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Download Hi-Res ImageDownload to MS-PowerPointCite This:Environ. Sci. Technol. 2023, 57, 31, 11572-11582
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Occurrence, Fate, and Transport of Contaminants in Indoor Air and Atmosphere

Time-Resolved Molecular Characterization of Secondary Organic Aerosol Formed from OH and NO3 Radical Initiated Oxidation of a Mixture of Aromatic Precursors
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Cite this: Environ. Sci. Technol. 2023, 57, 31, 11572–11582
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https://doi.org/10.1021/acs.est.3c00225
Published July 26, 2023

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Abstract

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Aromatic hydrocarbons (ArHCs) and oxygenated aromatic hydrocarbons (ArHC–OHs) are emitted from a variety of anthropogenic activities and are important precursors of secondary organic aerosol (SOA) in urban areas. Here, we analyzed and compared the composition of SOA formed from the oxidation of a mixture of aromatic VOCs by OH and NO3 radicals. The VOC mixture was composed of toluene (C7H8), p-xylene + ethylbenzene (C8H10), 1,3,5-trimethylbenzene (C9H12), phenol (C6H6O), cresol (C7H8O), 2,6-dimethylphenol (C8H10O), and 2,4,6-trimethylphenol (C9H12O) in a proportion where the aromatic VOCs were chosen to approximate day-time traffic-related emissions in Delhi, and the aromatic alcohols make up 20% of the mixture. These VOCs are prominent in other cities as well, including those influenced by biomass combustion. In the NO3 experiments, large contributions from CxHyOzN dimers (C15–C18) were observed, corresponding to fast SOA formation within 15–20 min after the start of chemistry. Additionally, the dimers were a mixture of different combinations of the initial VOCs, highlighting the importance of exploring SOAs from mixed VOC systems. In contrast, the experiments with OH radicals yielded gradual SOA mass formation, with CxHyOz monomers (C6–C9) being the dominant constituents. The evolution of SOA composition with time was tracked and a fast degradation of dimers was observed in the NO3 experiments, with concurrent formation of monomer species. The rates of dimer decomposition in NO3 SOA were ∼2–3 times higher compared to those previously determined for α-pinene + O3 SOA, highlighting the dependence of particle-phase reactions on VOC precursors and oxidants. In contrast, the SOA produced in the OH experiments did not dramatically change over the same time frame. No measurable effects of humidity were observed on the composition and evolution of SOA.

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Synopsis

This study examines the composition of SOA formed by the reactions of a mixture of aromatic VOCs with OH and NO3 radicals, as well as the role of intra-particle reactions in the evolution of SOA composition.

1. Introduction

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In urban areas, anthropogenic volatile organic compounds (VOCs), emitted by vehicular exhaust, biomass burning, and use of solid fuels, (2,3) are a major fraction of the total VOCs present. (1,4,5) The main contributors to anthropogenic VOCs present in these environments are aromatic hydrocarbons such as benzene (C6H6), toluene (C7H8), ethylbenzene (C8H10), and tri-methylbenzene (C9H12), which are henceforth termed as ArHCs in this study. ArHCs and their associated alcohols (denoted ArHC–OHs here) can contribute to urban O3 pollution, (6,7) photochemical smog, (8) and secondary organic aerosol (SOA) formation. (9,10) In addition, the SOA formed from oxidation of these precursors is known to have adverse effects on human health. (11−13) It has been shown that the oxidative potential (OP) of particulate matter (PM) (i.e., the ability of particles to generate reactive oxygen species (ROS) and create an imbalance in the favor of oxidants) depends on both its concentration and composition, (14−16) with SOA identified as an important contributor to OP. Recently, the non-exhaust vehicular emissions and anthropogenic SOA were shown to be the largest contributors to aerosol OP throughout most of Europe. (17) These findings support the observations in Delhi, (18) where the OP was highest during the afternoon period when the PM mass is dominated by SOA formed from aromatic precursors. (19) These observations suggest a link between the SOA formed from the anthropogenic precursors and increased health risks.
The oxidation of anthropogenic VOCs in the atmosphere is driven by the initial attack of an oxidant (OH or NO3) on the parent VOC followed by addition of O2, which generally results in the formation of a peroxy (RO2) radical. (20−22) The fate of these RO2 radicals depends upon the concentration of NOx (NO + NO2) and other radicals present in the atmosphere (e.g., HO2, RO2 and NO3). In a low-NOx regime, RO2 radicals predominantly react with HO2 and other RO2 radicals (including self-reactions), or undergo autoxidation to form highly oxygenated molecules. (23−25) In a high-NOx regime, RO2 radicals predominantly react with NO to produce organo-nitrates (RONO2) or proceed to form alkoxy radicals (RO) which fragment into smaller molecules, thereby reducing the amount of SOA formed. (26,27) Depending upon the fate of RO2 radicals, different oxidation products may be produced in the gas phase, some of which may then partition into the particle phase to form SOA.
Recent studies of α-pinene SOA have shown that the composition of SOA is not solely governed by gas-particle partitioning, but additionally by particle-phase reactions, which include reactions under dark conditions. (28,29) These reactions alter the chemical composition of the particles and may alter the physical properties of SOA. The changes brought about by the particle-phase reactions can be rapid, for example, half-lives of some decaying species are less than an hour. (28) In addition, the ROS such as peroxides, which are linked to oxidative stress and detrimental health effects, have been shown to be reactive and have short lifetimes. (30,31) Owing to these reasons, it becomes essential to conduct highly time-resolved measurements to study the changes occurring on timescales of minutes to hours in chamber/laboratory settings and accurately associate them with comparable atmospherically relevant time scales to better constrain the health effects and chemical properties of SOA.
Chamber studies focused on the oxidation of ArHCs have mostly concentrated on mechanistic and compositional aspects of SOA from single-component aromatic systems. (9,32−34) The atmosphere, however, comprises a mixture of different VOCs that oxidize simultaneously. The oxidation of a mixture of VOC precursors, together, may produce oxidation products from cross-reactions of RO2 radicals produced from different initial VOCs, thus leading to a different SOA composition than that expected from oxidation of single VOC precursors or a simple summation of their respective products. (35,36) Product interactions may produce SOA with different physical and chemical properties as compared to a single-component SOA. (35,37−39) Therefore, studying the oxidation of mixtures of VOC precursors will better represent the composition of SOA in urban areas. Additionally, as OH and NO3 radicals dominate the daytime and nighttime oxidation, respectively, of these VOCs, a comparison between SOA composition produced by OH and NO3 chemistry can provide valuable insights.
Here, we used an extractive electrospray ionization mass spectrometer (EESI-TOF) and an aerosol mass spectrometer (AMS) to measure the bulk composition of SOA formed from the oxidation of an aromatic mixture (including ArHC and ArHC–OH molecules) by either OH or NO3 radicals. The high time resolution of the EESI-TOF makes it possible to follow the changes in SOA composition in real-time, determining the processes driving compositional changes. We also compared the rates of decay of some high-molecular weight species observed in the aromatic + NO3 system in this study with those observed in the α-pinene + O3 system.

2. Methodology

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2.1. Instrumentation

The Aerodyne AMS (40,41) was used to obtain quantitative measurements of the size-resolved composition of non-refractory (NR; species that flash-vaporize at 600 °C) PM at high time resolution. Here, the sampled aerosol particles pass through an aerodynamic lens and get focused into a particle beam which impact on a heated tungsten surface (∼600 °C, and ∼10–7 Torr) and the NR components flash-vaporize. The resulting vapors are ionized by electron ionization (EI, ∼70 eV) and analyzed by a TOF mass spectrometer.
The extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) measured the near-molecular level composition (i.e., chemical formulae of the molecular ions) of the SOA formed in the chamber. (28,29,42,43) Here, the aerosol sample is drawn at 1 L min–1 through a multi-channel charcoal denuder (69 channels, volume of 38 cm3) to remove the gaseous components. After this, the aerosol sample intersects a charged spray of droplets (50:50 water/acetonitrile, doped with 100 ppm of NaI) emitted by an electrospray capillary (2900 V). The soluble components of the sampled aerosol are extracted in the charged droplets. During evaporation and subsequent Coulomb explosion, the analyte molecules are ejected as Na+ adducts. These adducts are guided into a commercial time-of-flight mass spectrometer and analyzed according to their m/z. The average resolution of the mass spectrometer was between 9000 and 10,000 M/ΔM at m/z 185 during all experiments. Additional details on AMS and EESI-TOF data analysis are given in Supporting Information S2 and a comparison of EESI-TOF mass flux, AMS and SMPS is given in Figure S2.

2.2. Chamber Experiments

A series of experiments was designed to study the composition and evolution of SOA formed from the oxidation of a mixture of aromatic compounds with OH and NO3 radicals. Experiments were conducted in the Paul Scherrer Institute (PSI) atmospheric simulation chamber, (44) which consists of a 9 m3 volume (2.5 m × 1.8 m × 1.9 m, L × W × H), 125 μm thick collapsible bag made of fluorinated ethylene propylene. In containers next to the chamber, the following instruments were installed: an O3 monitor (Thermo 49c), a NOx monitor (Thermo 42c), a proton-transfer reaction time-of-flight mass spectrometer (PTR-MS, Ionicon PTR 8000), a scanning mobility particle sizer (SMPS, TSI model 3938), a high-resolution time-of-flight AMS (Aerodyne Research, Inc.), and an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF, Tofwerk AG). Prior to each experiment, the chamber was cleaned overnight by continuously flushing with 40 L min–1 of pure air from a zero-air generation system (737-250 series, AADCO Instruments, Inc., USA). Prior to the start of each experiment, the particle number concentration was checked by the SMPS, and if the total number concentration was below 10 cm–3, the chamber was deemed clean.
These experiments focused on the oxidation of a mixture of ArHC and ArHC-OH molecules with both NO3 radicals and OH radicals at 40–50 and 70–90% relative humidity (RH). A single ArHC + ArHC–OH mixture was used for all experiments, and consisted of toluene (C7H8), p-xylene + ethylbenzene (1:1 (v/v); C8H10), 1,2,3-tri-methylbenzene and 1,3,5-tri-methylbenzene (1:1 (v/v); C9H12), phenol (C6H6O), o-, m- and p-cresol (1:1:1 (v/v); C7H8O), 2,3-dimethylphenol (C8H10O), and 2,4,6-trimethylphenol (C9H12O). This VOC mixture was designed such that the ratios of toluene, p-xylene + ethylbenzene, and tri-methylbenzene in this mixture were ∼6:4:1 on a volume-to-volume (v/v) basis and approximately similar to the ratios of these VOCs in the mass spectrum of a traffic-related factor from a recent VOC source apportionment study in Delhi, which dominated the daytime emissions. (1) Substituted aromatics, that is, phenol, cresol, 2,6-dimethylphenol, and 2,4,6-trimethylphenol, were added in equal amounts and constituted in total ∼20% by volume of this mixture. The approximate concentrations of the VOCs after injection into the chamber are given in Table S1.
The experimental protocols differed between the OH and NO3 experiments and are discussed in detail in the Supporting Information S1. Table S2 summarizes the experimental conditions of all experiments conducted. In all experiments, the mass measured by the SMPS was corrected for particle wall loss (Supporting Information S3). A size-dependent wall loss was applied to different species measured by the AMS (Figure S10).
During the course of the OH experiments, there was an integrated OH exposure of 5.67 × 107 molec cm–3 h, which is equivalent to about 56.7 h or 2.4 day equivalents of atmospheric aging assuming a global average OH concentration of 1 × 106 molec cm–3. Note that this value is taken from Experiment 5 (due to the PTR-MS not operating for the other OH experiments; see Table S2) and assumed to approximately hold for the other OH experiments, given the same lights and identical HONO production. More details on the calculation of OH exposure are given in Supporting Information S4.
The NO3 concentrations were modeled with F0AM (see next section) to provide an upper limit on the NO3 exposure in the chamber, which under our experimental conditions corresponds to ∼30 days of aging in ∼3 h of experimental time.

2.3. Chamber Box Modeling

The Framework for 0-D Atmospheric Modeling (F0AM) with the Master Chemical Mechanism (MCM) was used to model the radical chemistry and reactivity of precursor VOCs in the chamber. (45) The model incorporates the reactions in the MCM (46,47) to simulate atmospherically relevant chemical systems. The initial concentrations of VOCs in the chamber were used as model inputs. The model was run with the same initial concentrations of VOCs for simulating both OH and NO3 reactions.

3. Results and Discussion

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In this section, we will only discuss the experiments conducted at 50% RH. The experiments conducted at 90% RH were evaluated to determine whether there were any systematic changes in SOA composition with an increase in RH. As this was not the case (see Figure S1), the high RH experiments are treated here as replicates.

3.1. VOC Consumption and SOA Formation

In the experiments conducted here, SOA formation from the same mixture of ArHC and ArHC–OH was probed using either NO3 or OH radicals. The reactivity of the VOC mixture depends strongly on the oxidant identity: the ArHC and ArHC–OH molecules used here have reaction rates with OH radicals spanning roughly an order of magnitude (on the order of 10–11 to 10–12 cm3 molec–1 s–1) while with NO3 they differ by almost 5 orders of magnitude (for ArHC ∼ 10–17 cm3 molec–1 s–1 and for ArHC–OH ∼ 10–12 cm3 molec–1 s–1). (48,49) Figure S3 models the expected reactivity of NO3 and OH radicals toward both ArHC and ArHC–OH molecules using F0AM coupled to the MCM (see Section 2.3), which agrees with the observed ArHC and ArHC–OH time series from the PTR-MS (Figure S3). Therefore, the difference in reactivity will result in nearly exclusive reactions of ArHC–OH + NO3. In contrast, for the OH experiments, a constant mixing ratio of ∼50 ppbv of HONO in the chamber leads to the model prediction that both ArHC and ArHC–OH will steadily react away, which agrees with the measured VOC consumption and the corresponding calculated OH exposure based on the differential reactivity of d9-butanol (fragment at mass-to-charge ratio m/z 66.126, [C4D9]+) and toluene (fragment at m/z 93.15, [C7H8]H+). (50)
Figure 1a,b shows organics, sulfate, and nitrate concentrations measured by the AMS for the NO3 and OH experiment, respectively. In both sets of experiments, formation of organic mass is observed after the start of chemistry. However, the rate of SOA formation differs between the experiments, with formation occurring almost exclusively during the first 30 min for the NO3 experiment (Figure 1a), contrasting with steady formation over the entire 4 h for the OH experiment (Figure 1b). It should be noted that the initial rate of VOC consumption and SOA formation relates to different protocols used for radical introduction where a presumably large burst of NO3 radicals was formed in the starting vs a continuous formation of OH radicals. The formation rates of SOA in Figure 1a,b are consistent with the differences in VOC consumption shown in Figure S3. Additionally, the difference in the magnitude of SOA formed from each experiment relates to the concentration and identity of the VOCs available to react in the chamber. Because the same mixture was used for both experiments but only the ArHC–OH subset has significant reactivity with NO3, the OA concentrations obtained in these experiments are lower than in the OH experiments. The SOA yield from the OH experiment was 5.2%, which is higher than that from the NO3 system by more than a factor of 2. Further, Mutzel et al. (2021) (33) reported that the SOA yield from cresol + NO3 was only 1% in the experiments conducted at lower organic mass concentrations (a factor of ∼5 lower than in our experiments). In contrast, we observed an aggregate SOA yield of 2% for the NO3 experiment. This variation in yield could be attributed to different partitioning behaviors under different organic mass concentrations, as well as the impact of a mixture of VOCs (i.e., multiple VOCs with interacting products) on the overall SOA yield.

Figure 1

Figure 1. SOA mass evolution after the start of chemistry for (a) aromatics + NO3 and (b) aromatics + OH. Also included are the particle-phase nitrate and sulfate concentrations measured by the AMS. Note, the background of NO3– is ∼1 μg m–3 in our OH experiments, which may come from incorporation of HNO3 left over from the NO3 experiments. The zero on the x-axis represents the time of the start of the reaction, i.e., when VOCs are first exposed to radicals. Pink shading denotes the time periods used to determine representative mass spectra for the aromatics + NO3 (c) and aromatics + OH (d) systems. These mass spectra are represented as carbon number distributions, with bins divided into CHO (left bar, blue-purple-green shading) and CHON (right bar, yellow-red-brown shading), and stacked vertically by number of oxygen atoms.

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3.2. SOA Composition

3.2.1. SOA Composition Measurements by EESI-TOF

To highlight the detailed changes in the composition, the characteristic EESI-TOF mass spectra are binned according to the number of carbon atoms and stacked according to the number of oxygen atoms in Figure 1c,d, for the NO3 and OH experiment, respectively. For each carbon number, the column on the left indicates the observed CHO molecules and the column on the right indicates the observed CHON molecules. The molecular SOA composition in the NO3 experiment (Figure 1c) is dominated by nitrogen-containing species, with CxHyOzN molecules constituting ∼65.9% of the measured signal and the remainder (∼34.1%) comprising CxHyOz molecules. Dimers (with carbon numbers C12 to C18) make up 54.2% of the signal, with the majority being CxHyOzN dimers constituting 42.3% of the total signal. In contrast, the composition of SOA formed from OH radicals is dominated by CxHyOz molecules, constituting ∼75% of the total signal with the remainder (∼25%) coming from CxHyOzN species. Note, the dimer distribution peaks at C16 molecules while the other two most important dimers formed in the NO3 experiments (C15, C17) must come from reactions between pairs of different VOCs (e.g., C8 + C7 or C8 + C9). Table S3 shows the ratio of H-abstraction vs NO3 addition varies greatly with the molecular structure of the species. For less substituted alcohols, the H-abstraction is favored over NO3 addition but for highly substituted species such as trimethylbenzene, the NO3 addition is the dominant pathway. The H-abstraction pathway leads to an alkoxy radical, while the NO3-addition pathway leads to an RO2 radical. Therefore, we expect that the larger aromatic alcohols will form a larger fraction of dimers from RO2 radicals, which is consistent with our observations where there is higher prevalence of N-containing dimers with C > 15 in NO3 experiments. This highlights how the mixture of gases present will influence the amount of SOA formed, since they are dependent on the other oxidation products present. Similar results have been shown for mixtures of monoterpenes recently. (51,52) Further, for the OH experiment, dimers (C12–C18) only make up a small fraction of the total measured contribution (∼6.5% in total for CxHyOz (4.6%) and CxHyOzN (1.9%)), while the CxHyOz and CxHyOzN monomers (C5–C9) comprise ∼64.7 and ∼22.5% of the total EESI mass flux, respectively. It should be noted that the method used to produce OH radicals (HONO photolysis) results in a steady presence of NOx in the chamber. We observed the presence of approximately 1 ppbv of NO, with NO2 levels gradually increasing over time. This leads to a substantial fraction of CHON type species being formed in the particle phase, as observed. The remainder of the composition (∼6%) is composed of C10 (5.5%) and C11 (0.5%) species. Here, the importance of the mixed reaction products is smaller, given the smaller fraction of dimers, but odd carbon products (C13 and C15) again indicate the influence of mixed VOC reaction products.
Formation of SOA is governed by gas-particle partitioning of molecules possessing sufficiently low saturation vapor concentration to partition into the particle phase. The formation of low-volatility molecules occurs through oxidation reactions in the gas-phase and their subsequent radical reaction pathways. In reactions of ArHC–OH molecules with NO3 radicals, the dominant fate of RO2 radicals is either RO2 + RO2 or RO2 + NO3 reactions, because HO2 is not expected to be formed during these experiments. The radical balance in the chamber was modeled using F0AM to simulate the reactivity of first-generation RO2 radicals formed by the reaction of cresol with NO3 radicals (Figure S4a), where RO2 radicals are expected to react almost exclusively with other RO2 radicals forming self- or cross-reaction products (dimers). Recent work demonstrates the importance of RO2 + RO2 reactions as a pathway for dimer formation, (53−56) which is likely the dominant source of dimers observed in Figure 1c. Dimers formed via this pathway will possess sufficiently low saturation vapor concentrations for condensation, resulting in rapid formation of SOA mass, consistent with the large fraction of dimers present in Figure 1c. This pathway is also likely responsible for the formation of mixed oxidation products, and their inclusion in the SOA.
In contrast, the OH experiments have significant concentrations of HO2 radicals and relatively lower concentrations of RO2 radicals because of a continuous injection of HONO instead of a single large burst of radicals as occurs in the NO3 experiments. This leads to continuous reactions of precursor VOCs + OH, rather than prompt consumption of all reactive VOCs. In addition, in the case of the OH experiments, we have NO and HO2 radicals available which will drive the RO2 chemistry toward RO2 + NO and RO2 + HO2 reactions. Figure S4b shows the simulated reactivity of a representative first-generation RO2 radical formed from toluene + OH, where the expected fate of RO2 radicals is dominated by reactions with HO2 and NO, with negligible RO2 + RO2 reactions. Therefore, the contribution of dimers formed in the gas phase will also be minor, consistent with the small dimer fraction observed in Figure 1d. The difference in modeled radical regimes present in each experiment (NO3 vs OH) provides an initial explanation of the monomer and dimer distributions present in Figure 1c,d, and also why the magnitude of cross VOC products is smaller for the OH chemistry system.
In addition to the differences in the detailed chemical composition observed in both experiments, these experiments differ also in terms of bulk elemental ratios. As measured by the EESI-TOF, the average O/C ratios are ∼0.45 and ∼0.72 for the NO3 and OH experiments, respectively, while the N/C ratios are ∼0.055 and ∼0.030 for the NO3 and OH experiments, respectively. A point to note here is that the N/C ratios in the NO3 and OH experiments differ by less than a factor of 2, despite having substantially different contributions of nitrogen containing species (CxHyOzN) to the total EESI signal in the respective experiments (as mentioned above in this section). This can be explained by the fact that most of the nitrogen in the NO3 experiment is contained in the dimers which have lower N/C ratio than monomers, whereas in the OH experiment all the nitrogen are found in the monomer species. As a result, despite having substantially different contributions of nitrogen containing compounds, N/C is not substantially different in the NO3 and OH experiments. Nevertheless, the elemental ratios from the EESI-TOF show some differences in SOA composition between NO3 and OH experiments, but because the EESI-TOF has ion-dependent sensitivities, (42,57) a quantitative overview can only be obtained by analyzing the elemental ratios observed by the AMS.

3.2.2. AMS SOA Composition

Figure 2a,b shows the time series of elemental ratios (i.e., O/C, H/C and N/C) determined by the AMS (58,59) for the NO3 and OH experiments, respectively. There is a considerable difference in the level of oxygenation for the NO3 (mean value of 0.54) vs OH (mean value of 1.01) experiments, which is consistent with the differences observed by the EESI-TOF between the OH and NO3 experiments. The N/C ratios measured by the AMS lie in the range (0.012–0.016) for the NO3 experiments and (0.012–0.019) for the OH experiment and are, in both the NO3 and OH experiments, a factor of 3–5 lower than those of the EESI (Figure S5). This is most likely the result of a combination of two factors: (1) breakdown of organonitrates to the inorganic ions NO+ and NO2+ in the AMS, which are then not included in the SOA organic mass calculation nor the bulk elemental ratios, and potentially (2) uncertainties in ion-specific response factors in the EESI-TOF. (60) Nevertheless, the temporal experimental trends observed by the two instruments agree with each other for both the OH and NO3 experiments (Figure S5). As a comparison, the O/C ratios of logwood combustion emissions were reported to lie between 0.74 and 0.83 after 4 h of dark aging by NO3 radicals, (61) whereas for single component systems, for example, SOA from m-xylene or toluene with OH radicals under high NOx conditions were reported to lie between 0.68 and 0.72. (62) In the experiments presented here, oxidation by the OH radicals systematically yields a higher level of oxygenation in SOA than does oxidation by the NO3 radicals. One explanation for the lower degree of oxygenation in the NO3 experiments is that the dominance of RO2 + RO2 results in the formation of dimers with comparatively lower O/C ratios while in the OH experiments, the first- and second-generation products can undergo further oxidation with OH leading to a higher degree of oxygenation. These explanations also explain the evolution of the O/C ratio with time, where there is a large increase in the O/C ratio in the OH experiment, and a slightly increasing value in the NO3 experiment within the first 2 h.

Figure 2

Figure 2. Time-series O/C, H/C, and N/C ratios obtained from the AMS for (a) NO3 experiment and (b) OH experiment.

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Beyond the evolution of the O/C ratio, the N/C ratio also continually evolves in both experiments. In the OH experiments, the N/C ratio gradually grows from 0.013 to 0.019 (SD = 0.002), which may be explained by the increased formation of organonitrates from the increasing NOx availability in the chamber resulting from HONO photolysis. In the NO3 experiments, the N/C ratio measured by the AMS rapidly increases in the first 30 min and then steadily decreases from 0.016 to 0.012 (SD = 0.002) from 30 to 240 min. Similarly, the EESI-TOF N/C ratio shows a rapid increase and then a continuous decrease (Figure S5). This indicates that the chemical composition of the SOA in the NO3 experiments evolves with time even in the absence of large changes in OA mass concentration, and that these changes exert considerable influence on the bulk composition.

3.3. Evolution of the SOA Molecular Composition with Time

The ongoing changes in the bulk composition demonstrated in the previous section can be further interrogated by the EESI-TOF spectral evolution. Figure 3a,b shows the time-dependent evolution of the carbon number distributions (i.e., Figure 1c,d) for the NO3 and OH experiment, respectively, with CxHyOz and CxHyOzN molecules distinguished by the shading pattern. For the NO3 experiment, the fractional contribution of dimer species (C15–C18) decreases with time (Figure S7), corresponding to increases in the fraction of both CxHyOz (C7HyOz, C8HyOz, and C9HyOz) and CxHyOzN (C9) monomers. Figure S6 shows some key species that increase over the course of the experiment, including C9H12O3, C9H14O4, C9H13NO7, C8H12O4, and C7H8O3. The total wall loss-corrected organic mass slightly increases between 30 and 240 min after the start of chemistry (Figure 1a) coinciding with the period during which the dimer decay is most prevalent, indicating there is likely minimal evaporation from the particle phase. Because the relative sensitivities of the EESI-TOF toward dimers vs monomers are not well constrained, the actual dimer and monomer fractions might be different from what is observed here. Considering the VOCs are completely consumed after ∼10 min during the NO3 experiments, the changes in particle-phase composition are likely driven by intra-particle reactions. The loss of dimers cannot be explained by evaporation because dimers are expected to have lower saturation vapor concentrations than their corresponding monomers and should not readily evaporate under our experimental conditions. Particle-phase reactions have also been shown to occur in α-pinene SOA derived from both NO3 and O3. (28,29,43) In the experiments presented here, the main process governing the change in composition is the decay of dimers to form smaller molecules, specifically CHO and CHON monomers. This proposed dimer-to-monomer conversion differs from the particle-phase reactions observed in α-pinene + O3 experiments (28) where the dominant process was a shift from higher carbon number species to lower carbon number species within monomers and dimers (and without substantial evidence of dimer-to-monomer conversion). The presence of NO2 and O3 in the chamber can lead to the formation of N2O5 which can hydrolyze quickly and can lead to the formation of NO3 ions that react with organic material in the particle phase to form nitrogen containing SOA species. However, the absence of a significant increase in particle phase NO3 suggests that the majority of changes observed in the SOA composition during the NO3 experiments are due to particle phase reactions, rather than later generation gas-phase chemistry involving N2O5. It is worth noting that the MCM in its current form does not include pathways for multi-generation NO3 chemistry.

Figure 3

Figure 3. (a) Temporal evolution of fractional contributions from species in the aromatics + NO3 experiment color-coded by their carbon number (b) Same plot for the aromatics + OH experiment. (c) Mass-defect plot (exact mass minus nearest integer mass vs m/z) color-coded by ratio of intensity at 210 min to intensity at 30 min for the aromatics + NO3 system. Closed circles depict CHO C6–C9 monomers, whereas open circles depict CHO C13–C18 compounds. The closed and open diamonds depict CHON monomer and dimer species, respectively. (d) Mass-defect plot color-coded by ratio of intensity at 210 min to intensity at 30 min for the aromatics + OH system.

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Figure 3b shows the time evolution of the carbon number distribution for the OH experiment, showing much less change in the SOA composition than for the NO3 experiments (Figure 3a). Here, the fractional contribution from CHON species changes from ∼27% after ∼1 h to ∼19% after ∼4 h from the start of the experiment. Similarly, the fractional contribution of CHO species increases from ∼73 to ∼81% during the same time. The SOA composition from the OH oxidation (Figure 3b) is dominated by monomer CHO species with carbon number C6–C9. Although a slight increase in the fractional contributions from higher carbon number species (>C9) is observed with time, this is a minor contribution (increasing to a total of ∼4% at the end of experiment) in comparison with the NO3 experiments (∼55% at the beginning of the experiment and ∼27% at the end). However, this does not necessarily indicate the absence of particle-phase processes during OH oxidation, but rather that the overall SOA composition is dominated by the continuous formation of low-volatility material in the gas-phase which partitions into the particles, which could obscure the effects of particle-phase reactions in the OH system. Further, other studies have shown that multi-generation chemistry taking place in the gas-phase are responsible for the continued formation of SOA later in the experiment. (63) This contrasts with the NO3 experiments, where all reactive VOCs are consumed within the first 10–15 min, and limited multi-generation chemistry is taking place.
Figure S8 shows the time series of selected CHON dimers (grouped by hydrogen number), which decay during the course of the NO3 experiment. There are a variety of different decay rates during the initial aging period, with some of the molecules (e.g., C17H19NOx) decaying much faster (decay rate = 0.034 min–1) than others (e.g., C16H15NOx; decay rate = 0.022 min–1). Additionally, the extent of the decay (i.e., fraction remaining) differs from molecule to molecule. To highlight these differences, Figure 3c,d shows mass-defect plots color-coded by the ratio of signal at 210 vs 30 min after the start of chemistry, that is, EESI (t210)/EESI (t30) for the NO3 (Figure 3c) and OH experiments (Figure 3d). Different symbols denote CHO and CHON monomers (C6–C9) and dimers (C13–C16).
For the NO3 experiment (Figure 3c), nearly all CHON dimers (open diamonds) exhibit EESI (t210)/EESI (t30) < 1, with most decreasing by more than 75%. This feature is not observed for CHO dimers, which range from a ∼30% increase to ∼30% decrease. CHON monomers are quite variable, ranging from a ∼75% decrease to a ∼75% increase. CHO monomers show a similar behavior, though relative to CHON they are more likely to show an increase (or smaller decrease). Figure 3a,c implies that in the NO3 experiments, CHON dimers decompose into smaller molecules, likely including both CHON and CHO. The observations cannot be explained by evaporation, which would result in lower carbon number dimers decaying faster than higher carbon number dimers. The opposite trend is observed here (higher mass compounds decay more quickly) and is therefore attributed to particle-phase decomposition reactions.
Overall, the SOA composition changes dramatically over the course of the NO3 experiment, where the initial composition is ∼25% monomers and ∼75% dimers, ultimately changing to ∼65% monomers and ∼35% dimers. Although variations in molecule-dependent EESI-TOF sensitivities make these compositional changes difficult to interpret quantitatively, they correspond well with the changes in the bulk N/C ratio from the AMS shown in Figure 2a. There, the N/C ratio decreases by ∼25% from t = 30 min to t = 210 min, and likely reflects the conversion of CHON dimers to CHO monomers, which in turn suggests that the changes observed in the EESI-TOF indeed reflect a considerable change in bulk composition. Although the AMS measurements do not provide a comparable means of assessing CHON dimers vs CHON monomers, given the similar behavior of CHO and CHON monomers, we consider it likely that the CHON dimer-to-monomer conversion likewise has a considerable impact on the bulk composition. To further probe this effect, the fraction of organonitrates to total OA was calculated from the AMS NO/NO2 ratio following the method described in Kiendler-Scharr et al. (2016). (64) Figure S9 indicates rapid organonitrate formation consistent with the observations by the EESI-TOF. Over the course of the experiment, however, the total organonitrate fraction remains stable in the AMS data. This contrasts with the EESI-TOF signal where the contribution of CHON compounds to total signal decreases from a maximum of ∼60 to ∼45% over the course of 3 h. This may reflect a somewhat higher sensitivity of the EESI-TOF toward dimers, where the largest changes in CHON/CHO are observed.
Figure 3d shows the mass defect plot color-coded by the ratio of the intensity at 210 min after the start of chemistry to the intensity at 30 min, that is, EESI (t210)/EESI (t30) for the OH experiment. Most of the molecules that are increasing during the experiment are typically more highly oxygenated species consistent with an increasing O/C ratio observed by both AMS and EESI-TOF. Additionally, there are increases in smaller molecules (C6–C7), which could come from multi-generational chemistry from smaller early generation molecules (e.g., first-generation oxidation products of benzene/toluene or fragmentation products of C8/C9 species). The majority of species that decrease with experimental time are C9H12–14O4–7 and C9H11–15O5–8N. These molecules could either react (e.g., fragment) in the particle phase or undergo repartitioning into the gas-phase as they react away in the gas-phase and reestablish equilibrium. Distinguishing between these processes is not possible in the current experiments because they occur simultaneously. Nonetheless, these results highlight, for both radical systems, the continuously evolving composition of SOA.

3.4. Decay Rates of Dimer Species in the NO3 Experiment

For the NO3 experiment, decay rates were calculated for CxHyOzN species that decayed to less than 50% of their maximum signal (e.g., C7 and C8 monomers and C14–C17 dimers) by fitting an exponential (y = y0 + Ae–kt) to the individual time series from the time of the maximum signal to the end of the experiment. The offset (y0) is included because the species examined here do not decay to zero, presumably due to the presence of isomers with different functionalities as also concluded by Pospisilova et al. (2020). (28) The decay rate (k) determined by the fit is reported in min–1.
The decay rates shown in Figure 4 are aggregated according to the number of carbon atoms present in the molecular formulae. The fastest decaying dimers observed were C16 species, which had an average decay rate of 0.060 min–1 (n = 8), of which the fastest decaying species were C16H17NO4, C16H17NO5, and C16H19NO5 (decay rates of 0.08, 0.12, and 0.14 min–1, respectively). By comparison, the average decay rates of C17, C15, and C14 species were 0.034, 0.025, and 0.024 min–1, respectively. Figure 4 also shows the decay rates presented in Pospisilova et al. (2020) (28) from α-pinene + O3 SOA. For both monomers and dimers, the decay rates in the aromatic + NO3 system are faster than those in the α-pinene + O3 system. This may be due to the slower SOA formation in the α-pinene + O3 system compared to the aromatic + NO3 system studied here. The decay rates reported in both studies should be interpreted as lower limits, due to the potential for production during the decay period; the potential bias increases as SOA formation extends later into the experiment. For instance, in the α-pinene + O3 experiment, the maximum SOA mass was reached after 90–120 min, while for the mixture used in this study, the maximum SOA mass is reached after 15–20 min. A second difference is that all monomer and dimer species included are CxHyOz type compounds in the α-pinene + O3 system and CxHyOzN type compounds in the aromatic + NO3 system (CxHyOz type compounds excluded here). This suggests that the presence of a nitrate functional group may render a molecule more prone to particle-phase decomposition. The fast decomposition/decay of dimers implies the dimer linkage is likely prone to decomposition. This would fit the scenario that dimers are largely formed from RO2 + RO2 chemistry, where the peroxy linkage may be unstable, favoring decomposition to the constituent monomers.

Figure 4

Figure 4. Box–whisker plots of decay rates calculated for CxHyOz type C9–C10 monomers and C20 dimer species in α-pinene + O3 SOA (28) highlighted by green areas. The points inside the respective box depict the mean rate of decay, whereas the diamonds adjacent to the boxed depict the spread of data. Similarly, the decay rates highlighted by pink areas are from CxHyOzN type C7–C8 monomers and C14–C17 dimers observed in the aromatics + NO3 system in this study.

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4. Implications

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In the nocturnal atmosphere, the RO2 + RO2 reactions could be an important sink for RO2 radicals depending upon the availability of HO2 and NO3 radicals, (65) and NO. Our study demonstrates, in the NO3 experiments, the importance of nitrogen containing dimer species presumably formed through RO2 + RO2 reactions leading both to mixed VOC oxidation products and fast formation of SOA. After formation, the NO3-derived SOA evolves rapidly, in particular through the decomposition of CHON dimers to CHO and CHON monomer species. In the OH experiments, the chemical composition evolves steadily throughout the experiment; however, given the experimental conditions, this is presumably due to continuous formation of organic mass through the gas-phase chemistry.
The observation of rapid changes in composition in the absence of further oxidant exposure as observed in the NO3 experiments means that care is needed in relating SOA composition measured under controlled laboratory conditions to field observations. Specifically, aligning the chemical age of the laboratory and ambient SOA is critical to draw accurate conclusions regarding the contribution of reactive species in the particle phase (e.g., the CHON dimers observed here in the NO3 experiments), which likely contain health-relevant peroxy functionalities. Further, this suggests that semi-continuous measurement systems may systematically underestimate the importance of such decay-prone molecules due to ongoing decomposition reactions during the collection stage.
Our results also show that the evolution of SOA from aromatic + NO3 is significantly faster than of biogenic + O3 SOA, (28) implying that the identity of the precursor VOC and the oxidant affects the rate and extent of SOA evolution. This should, however, be determined by conducting comparison studies of SOA evolution formed from different precursor VOCs but under similar conditions and a range of different oxidants. In the ambient environment, the oxidation of VOCs will proceed at a much slower rate because of lower oxidant (OH and NO3) concentrations as compared to these chamber experiments, and the presence of both HO2 and NO will change the fate of RO2 radicals in the atmosphere. This will result in lower dimer concentrations due to the quadratic dependence of the dimer formation rate on the monomer RO2 radical concentration. Additionally, such fast decays would be difficult to observe because there would be a continued formation of all oxidation products due to a continuous exposure to radicals, as opposed to the NO3 experiments here where a single burst of NO3 radicals was used. This would create a near-constant source of the rapidly decaying molecules, and presumably they would decay after they partition to the particle phase. The fast decay reactions, hence, would not be easily observed in the atmosphere despite their effects on particle composition, underscoring the need for targeted laboratory studies, such as those performed here, to elucidate these reactions under controlled conditions.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.3c00225.

  • Detailed description of experimental protocols; data analysis and interpretation; and wall loss correction methods (PDF)

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Author Information

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  • Corresponding Authors
  • Authors
    • Varun Kumar - Laboratory of Atmospheric Chemistry, Paul Scherrer Institute (PSI), Villigen 5232, Switzerland;  Present Address: Institut National de l’Environnement Industriel et des Risques, Parc Technologique ALATA, 60550, Verneuil en Halatte, France
    • Urs Baltensperger - Laboratory of Atmospheric Chemistry, Paul Scherrer Institute (PSI), Villigen 5232, Switzerland
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This project was supported by the SDC Clean Air Project in India (grant no. 7F-10093.01.04), the Swiss National Science Foundation projects BSSGI0_155846 (IPR-SHOP), 200021_169787 (SAOPSOAG), 200020_188624 (MOLORG), and by the European Union’s Horizon 2020 research and innovation program through the EUROCHAMP-2020 Infrastructure Activity under grant agreement no. 730997.

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    Secondary org. aerosol (SOA) formation from the photooxidn. of m-xylene, toluene, and benzene is investigated in the Caltech environmental chambers. Expts. are performed under two limiting NOx conditions; under high-NOx conditions the peroxy radicals (RO2) react only with NO, while under low-NOx conditions they react only with HO2. For all three aroms. studied (m-xylene, toluene, and benzene), the SOA yields (defined as the ratio of the mass of org. aerosol formed to the mass of parent hydrocarbon reacted) under low-NOx conditions substantially exceed those under high-NOx conditions, suggesting the importance of peroxy radical chem. in SOA formation. Under low-NOx conditions, the SOA yields for m-xylene, toluene, and benzene are const. (36%, 30%, and 37%, resp.), indicating that the SOA formed is effectively nonvolatile under the range of Mo(>10 μg m-3) studied. Under high-NOx conditions, aerosol growth occurs essentially immediately, even when NO concn. is high. The SOA yield curves exhibit behavior similar to that obsd. by Odum et al. (1996, 1997a, b), although the values are somewhat higher than in the earlier study. The yields measured under high-NOx conditions are higher than previous measurements, suggesting a "rate effect" in SOA formation, in which SOA yields are higher when the oxidn. rate is faster. Expts. carried out in the presence of acidic seed aerosol reveal no change of SOA yields from the aroms. as compared with those using neutral seed aerosol.
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    Zhang, R.; Wang, G.; Guo, S.; Zamora, M. L.; Ying, Q.; Lin, Y.; Wang, W.; Hu, M.; Wang, Y. Formation of Urban Fine Particulate Matter. Chem. Rev. 2015, 115, 3803– 3855,  DOI: 10.1021/acs.chemrev.5b00067
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    Formation of Urban Fine Particulate Matter
    Zhang, Renyi; Wang, Gehui; Guo, Song; Zamora, Misti L.; Ying, Qi; Lin, Yun; Wang, Weigang; Hu, Min; Wang, Yuan
    Chemical Reviews (Washington, DC, United States) (2015), 115 (10), 3803-3855CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review concerning the fundamental chem. aspects relevant to urban fine particulate matter (PM) formation, particularly processes governing particle no., size, and chem. compn., are given. Topics discussed include: introduction; historical perspectives (London fog, Los Angeles smog, Beijing haze); urban fine PM origins (primary emissions, new particle formation); growth processes (org. matter gas/particle partitioning, org. matter particle phase reactions [hydration and acid-catalyzed reactions, basic species reactions], SO42- and NO3- formation, primary particle aging); atm. measurements (anal. techniques [gaseous aerosol precursors, PM], anal. approaches, spatiotemporal characteristics of no. concn., size, chem. compn.m,, and other urban fine PM properties); atm. modeling (primary PM and gas precursor emissions, gaseous and multi-phase chem. [gaseous photochem. oxidn. mechanism, new particle formation, multi-phase processes], regional transport and removal processes); and future directions and conclusions.
  11. 11
    Lund, A. K.; Doyle-Eisele, M.; Lin, Y.-H.; Arashiro, M.; Surratt, J. D.; Holmes, T.; Schilling, K. A.; Seinfeld, J. H.; Rohr, A. C.; Knipping, E. M.; McDonald, J. D. The effects of α-pinene versus toluene-derived secondary organic aerosol exposure on the expression of markers associated with vascular disease. Inhalation Toxicol. 2013, 25, 309– 324,  DOI: 10.3109/08958378.2013.782080
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    The effects of α-pinene versus toluene-derived secondary organic aerosol exposure on the expression of markers associated with vascular disease
    Lund, Amie K.; Doyle-Eisele, Melanie; Lin, Ying-Hsuan; Arashiro, Maiko; Surratt, Jason D.; Holmes, Tom; Schilling, Katherine A.; Seinfeld, John H.; Rohr, Annette C.; Knipping, Eladio M.; McDonald, Jacob D.
    Inhalation Toxicology (2013), 25 (6), 309-324CODEN: INHTE5; ISSN:0895-8378. (Informa Healthcare)
    To investigate the toxicol. effects of biogenic- vs. anthropogenic-source secondary org. aerosol (SOA) on the cardiovascular system, the Secondary Particulate Health Effects Research program irradn. chamber was used to expose atherosclerotic apolipoprotein E null (Apo E-/-) mice to SOA from the oxidn. of either α-pinene or toluene for 7 days. SOA atmospheres were produced to yield 250-300 μg/m3 of particulate matter and ratios of 10:1:1 α-pinene:nitrogen oxide (NOx):ammonia (NH3); 10:1:1:1 α-pinene:NOx:NH3:sulfur dioxide (SO2) or 10:1:1 toluene:NOx:NH3; and 10:1:1:1 toluene:NOx:NH3:SO2. Resulting effects on the cardiovascular system were assessed by measurement of vascular lipid peroxidn. (thiobarbituric acid reactive substance (TBARS)), as well as quantification of heme-oxygenase (HO)-1, endothelin (ET)-1, and matrix metalloproteinase (MMP)-9 mRNA expression for comparison to previous program exposure results. Consistent with similar previous studies, vascular TBARS were not increased significantly with any acute SOA exposure. However, vascular HO-1, MMP-9, and ET-1 obsd. in Apo E-/- mice exposed to α-pinene + NOx + NH3 + SO2 increased statistically, while α-pinene + NOx + NH3 exposure to either toluene + NOx + NH3 or toluene +NOx + NH3 + SO2 resulted in a decreased expression of these vascular factors. Such findings suggest that the specific chem. created by the presence or absence of acidic components may be important in SOA-mediated toxicity in the cardiovascular system and/or progression of cardiovascular disease.
  12. 12
    McDonald, J. D.; Doyle-Eisele, M.; Kracko, D.; Lund, A.; Surratt, J. D.; Hersey, S. P.; Seinfeld, J. H.; Rohr, A. C.; Knipping, E. M. Cardiopulmonary Response to Inhalation of Secondary Organic Aerosol Derived from Gas-Phase Oxidation of Toluene. Inhalation Toxicol. 2012, 24, 689– 697,  DOI: 10.3109/08958378.2012.712164
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    Cardiopulmonary response to inhalation of secondary organic aerosol derived from gas-phase oxidation of toluene
    McDonald, Jacob D.; Doyle-Eisele, Melanie; Kracko, Dean; Lund, Amie; Surratt, Jason D.; Hersey, Scott P.; Seinfeld, John H.; Rohr, Annette C.; Knipping, Eladio M.
    Inhalation Toxicology (2012), 24 (11), 689-697CODEN: INHTE5; ISSN:0895-8378. (Informa Healthcare)
    The biol. response to inhalation of secondary org. aerosol (SOA) was detd. in rodents exposed to SOA derived from the oxidn. of toluene, a precursor emitted from anthropogenic sources. SOA atmospheres were produced to yield 300 μg·m-3 of particulate matter (PM) plus accompanying gases. Whole-body exposures were conducted in mice to assess both pulmonary and cardiovascular effects. ApoE-/- mice were exposed for 7 days and measurements of TBARS and gene expression of heme-oxygenase-1 (HO-1), endothelin-1 (ET-1), and matrix metalloproteinase-9 (MMP-9) were made in aorta. Pulmonary inflammatory responses in both species were measured by bronchoalveolar lavage fluid (BALF) cell counts. No pulmonary inflammation was obsd. A mild response was obsd. in mouse aorta for the upregulation of ET-1 and HO-1, with a trend for increased MMP-9 and TBARS, and. Overall, toluene-derived SOA revealed limited biol. response compared with previous studies using this exposure protocol with other environmental pollutants.
  13. 13
    Tuet, W. Y.; Chen, Y.; Fok, S.; Champion, J. A.; Ng, N. L. Inflammatory Responses to Secondary Organic Aerosols (SOA) Generated from Biogenic and Anthropogenic Precursors. Atmos. Chem. Phys. 2017, 17, 11423– 11440,  DOI: 10.5194/acp-17-11423-2017
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    13
    Inflammatory responses to secondary organic aerosols (SOA) generated from biogenic and anthropogenic precursors
    Tuet, Wing Y.; Chen, Yunle; Fok, Shierly; Champion, Julie A.; Ng, Nga L.
    Atmospheric Chemistry and Physics (2017), 17 (18), 11423-11440CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Cardiopulmonary health implications resulting from exposure to secondary org. aerosols (SOA), which comprise a significant fraction of ambient particulate matter (PM), have received increasing interest in recent years. In this study, alveolar macrophages were exposed to SOA generated from the photooxidn. of biogenic and anthropogenic precursors (isoprene, α-pinene, β-caryophyllene, pentadecane, m-xylene, and naphthalene) under different formation conditions (RO2 + HO2 vs. RO2 + NO dominant, dry vs. humid). Various cellular responses were measured, including reactive oxygen and nitrogen species (ROS/RNS) prodn. and secreted levels of cytokines, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). SOA precursor identity and formation condition affected all measured responses in a hydrocarbon-specific manner. With the exception of naphthalene SOA, cellular responses followed a trend where TNF-α levels reached a plateau with increasing IL-6 levels. ROS/RNS levels were consistent with relative levels of TNF-α and IL-6, due to their resp. inflammatory and anti-inflammatory effects. Exposure to naphthalene SOA, whose arom.-ring-contg. products may trigger different cellular pathways, induced higher levels of TNF-α and ROS/RNS than suggested by the trend. Distinct cellular response patterns were identified for hydrocarbons whose photooxidn. products shared similar chem. functionalities and structures, which suggests that the chem. structure (carbon chain length and functionalities) of photooxidn. products may be important for detg. cellular effects. A pos. nonlinear correlation was also detected between ROS/RNS levels and previously measured DTT (dithiothreitol) activities for SOA samples. In the context of ambient samples collected during summer and winter in the greater Atlanta area, all lab.-generated SOA produced similar or higher levels of ROS/RNS and DTT activities. These results suggest that the health effects of SOA are important considerations for understanding the health implications of ambient aerosols.
  14. 14
    Shiraiwa, M.; Ueda, K.; Pozzer, A.; Lammel, G.; Kampf, C. J.; Fushimi, A.; Enami, S.; Arangio, A. M.; Fröhlich-Nowoisky, J.; Fujitani, Y.; Furuyama, A.; Lakey, P. S. J.; Lelieveld, J.; Lucas, K.; Morino, Y.; Pöschl, U.; Takahama, S.; Takami, A.; Tong, H.; Weber, B.; Yoshino, A.; Sato, K. Aerosol Health Effects from Molecular to Global Scales. Environ. Sci. Technol. 2017, 51, 13545– 13567,  DOI: 10.1021/acs.est.7b04417
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    14
    Aerosol Health Effects from Molecular to Global Scales
    Shiraiwa, Manabu; Ueda, Kayo; Pozzer, Andrea; Lammel, Gerhard; Kampf, Christopher J.; Fushimi, Akihiro; Enami, Shinichi; Arangio, Andrea M.; Frohlich-Nowoisky, Janine; Fujitani, Yuji; Furuyama, Akiko; Lakey, Pascale S. J.; Lelieveld, Jos; Lucas, Kurt; Morino, Yu; Poschl, Ulrich; Takahama, Satoshi; Takami, Akinori; Tong, Haijie; Weber, Bettina; Yoshino, Ayako; Sato, Kei
    Environmental Science & Technology (2017), 51 (23), 13545-13567CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    A review. Poor air quality is globally the largest environmental health risk. Epidemiol. studies have uncovered clear relationships of gaseous pollutants and particulate matter (PM) with adverse health outcomes, including mortality by cardiovascular and respiratory diseases. Studies of health impacts by aerosols are highly multidisciplinary with a broad range of scales in space and time. We assess recent advances and future challenges regarding aerosol effects on health from mol. to global scales through epidemiol. studies, field measurements, health-related properties of PM, and multiphase interactions of oxidants and PM upon respiratory deposition. Global modeling combined with epidemiol. exposure-response functions indicates that ambient air pollution causes more than four million premature deaths per yr. Epidemiol. studies usually refer to PM mass concns., but some health effects may relate to specific constituents such as bioaerosols, polycyclic arom. compds., and transition metals. Various anal. techniques and cellular and mol. assays are applied to assess the redox activity of PM and the formation of reactive oxygen species. Multiphase chem. interactions of lung antioxidants with atm. pollutants are crucial to the mechanistic and mol. understanding of oxidative stress upon respiratory deposition. The role of distinct PM components in health impacts and mortality needs to be clarified by integrated research on various spatiotemporal scales for better evaluation and mitigation of aerosol effects on public health in the Anthropocene.
  15. 15
    Liu, Q.; Baumgartner, J.; Zhang, Y.; Liu, Y.; Sun, Y.; Zhang, M. Oxidative Potential and Inflammatory Impacts of Source Apportioned Ambient Air Pollution in Beijing. Environ. Sci. Technol. 2014, 48, 12920– 12929,  DOI: 10.1021/es5029876
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    15
    Oxidative Potential and Inflammatory Impacts of Source Apportioned Ambient Air Pollution in Beijing
    Liu, Qingyang; Baumgartner, Jill; Zhang, Yuanxun; Liu, Yanju; Sun, Yongjun; Zhang, Meigen
    Environmental Science & Technology (2014), 48 (21), 12920-12929CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Air pollution exposure is assocd. with a range of adverse health impacts. Knowing the air pollution chem. components and sources most responsible for these health effects could lead to an improved understanding of effect mechanisms and more targeted risk redn. strategies. This work measured daily ambient fine particulate matter (PM2.5) for 2 mo in peri-urban and central Beijing, China, and assessed the contribution of its chem. components to the oxidative potential of ambient air pollution using the dithiothreitol assay. Compn. data were using in a multivariate source apportionment model to det. PM contributions of 6 factors/sources/: Zn, Al, and Pb point factors; and secondary source (e.g., SO42-, NO32-), Fe, and soil dust sources. The relationship between reactive oxygen species (ROS) activity-related PM sources and inflammatory responses in human bronchial epithelial cells was examd. In peri-urban Beijing, soil dust accounted for the largest fraction (47%) of measured ROS variability. In central Beijing, a secondary source explained the greatest fraction (29%) of measured ROS variability. ROS activity of PM collected in central Beijing was exponentially assocd. with in-vivo inflammatory responses in epithelial cells (R2 = 0.65-0.89). A high correlation was obsd. among 3 ROS-related PM sources (Pb point and Zn factors, secondary source) and inflammatory marker expression (r = 0.45-0.80). Results suggested large differences in the contribution of different PM sources to ROS variability in central vs. peri-urban sites in Beijing; secondary sources may play an important role in PM2.5-related oxidative potential and inflammatory health impacts.
  16. 16
    Bates, J. T.; Weber, R. J.; Abrams, J.; Verma, V.; Fang, T.; Klein, M.; Strickland, M. J.; Sarnat, S. E.; Chang, H. H.; Mulholland, J. A.; Tolbert, P. E.; Russell, A. G. Reactive Oxygen Species Generation Linked to Sources of Atmospheric Particulate Matter and Cardiorespiratory Effects. Environ. Sci. Technol. 2015, 49, 13605– 13612,  DOI: 10.1021/acs.est.5b02967
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    16
    Reactive Oxygen Species Generation Linked to Sources of Atmospheric Particulate Matter and Cardiorespiratory Effects
    Bates, Josephine T.; Weber, Rodney J.; Abrams, Joseph; Verma, Vishal; Fang, Ting; Klein, Mitchel; Strickland, Matthew J.; Sarnat, Stefanie Ebelt; Chang, Howard H.; Mulholland, James A.; Tolbert, Paige E.; Russell, Armistead G.
    Environmental Science & Technology (2015), 49 (22), 13605-13612CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Exposure to atm. fine particulate matter (PM2.5) is assocd. with cardiorespiratory morbidity and mortality, but the mechanisms are not well understood. We assess the hypothesis that PM2.5 induces oxidative stress in the body via catalytic generation of reactive oxygen species (ROS). A dithiothreitol (DTT) assay was used to measure the ROS-generation potential of water-sol. PM2.5. Source apportionment on ambient (Atlanta, GA) PM2.5 was performed using the chem. mass balance method with ensemble-averaged source impact profiles. Linear regression anal. was used to relate PM2.5 emission sources to ROS-generation potential and to est. historical levels of DTT activity for use in an epidemiol. anal. for the period of 1998-2009. Light-duty gasoline vehicles (LDGV) exhibited the highest intrinsic DTT activity, followed by biomass burning (BURN) and heavy-duty diesel vehicles (HDDV) (0.11 ± 0.02, 0.069 ± 0.02, and 0.052 ± 0.01 nmol/min μgsource, resp.). BURN contributed the largest fraction to total DTT activity over the study period, followed by LDGV and HDDV (45, 20, and 14%, resp.). DTT activity was more strongly assocd. with emergency department visits for asthma/wheezing and congestive heart failure than PM2.5. This work provides further epidemiol. evidence of a biol. plausible mechanism, that of oxidative stress, for assocns. of adverse health outcomes with PM2.5 mass and supports continued assessment of the utility of the DTT activity assay as a measure of ROS-generating potential of particles.
  17. 17
    Daellenbach, K. R.; Uzu, G.; Jiang, J.; Cassagnes, L.-E.; Leni, Z.; Vlachou, A.; Stefenelli, G.; Canonaco, F.; Weber, S.; Segers, A.; Kuenen, J. J. P.; Schaap, M.; Favez, O.; Albinet, A.; Aksoyoglu, S.; Dommen, J.; Baltensperger, U.; Geiser, M.; El Haddad, I.; Jaffrezo, J.-L.; Prévôt, A. S. H. Sources of Particulate-Matter Air Pollution and Its Oxidative Potential in Europe. Nature 2020, 587, 414– 419,  DOI: 10.1038/s41586-020-2902-8
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    Sources of particulate-matter air pollution and its oxidative potential in Europe
    Daellenbach, Kaspar R.; Uzu, Gaelle; Jiang, Jianhui; Cassagnes, Laure-Estelle; Leni, Zaira; Vlachou, Athanasia; Stefenelli, Giulia; Canonaco, Francesco; Weber, Samuel; Segers, Arjo; Kuenen, Jeroen J. P.; Schaap, Martijn; Favez, Olivier; Albinet, Alexandre; Aksoyoglu, Sebnem; Dommen, Josef; Baltensperger, Urs; Geiser, Marianne; El Haddad, Imad; Jaffrezo, Jean-Luc; Prevot, Andre S. H.
    Nature (London, United Kingdom) (2020), 587 (7834), 414-419CODEN: NATUAS; ISSN:0028-0836. (Nature Research)
    Abstr.: Particulate matter is a component of ambient air pollution that has been linked to millions of annual premature deaths globally1-3. Assessments of the chronic and acute effects of particulate matter on human health tend to be based on mass concn., with particle size and compn. also thought to play a part4. Oxidative potential has been suggested to be one of the many possible drivers of the acute health effects of particulate matter, but the link remains uncertain5-8. Studies investigating the particulate-matter components that manifest an oxidative activity have yielded conflicting results7. In consequence, there is still much to be learned about the sources of particulate matter that may control the oxidative potential concn.7. Here we use field observations and air-quality modeling to quantify the major primary and secondary sources of particulate matter and of oxidative potential in Europe. We find that secondary inorg. components, crustal material and secondary biogenic org. aerosols control the mass concn. of particulate matter. By contrast, oxidative potential concn. is assocd. mostly with anthropogenic sources, in particular with fine-mode secondary org. aerosols largely from residential biomass burning and coarse-mode metals from vehicular non-exhaust emissions. Our results suggest that mitigation strategies aimed at reducing the mass concns. of particulate matter alone may not reduce the oxidative potential concn. If the oxidative potential can be linked to major health impacts, it may be more effective to control specific sources of particulate matter rather than overall particulate mass.
  18. 18
    Puthussery, J. V.; Singh, A.; Rai, P.; Bhattu, D.; Kumar, V.; Vats, P.; Furger, M.; Rastogi, N.; Slowik, J. G.; Ganguly, D.; Prevot, A. S. H.; Tripathi, S. N.; Verma, V. Real-Time Measurements of PM2.5 Oxidative Potential Using a Dithiothreitol Assay in Delhi, India. Environ. Sci. Technol. Lett. 2020, 7, 504– 510,  DOI: 10.1021/acs.estlett.0c00342
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    18
    Real-Time Measurements of PM2.5 Oxidative Potential Using a Dithiothreitol Assay in Delhi, India
    Puthussery, Joseph V.; Singh, Atinderpal; Rai, Pragati; Bhattu, Deepika; Kumar, Varun; Vats, Pawan; Furger, Markus; Rastogi, Neeraj; Slowik, Jay G.; Ganguly, Dilip; Prevot, Andre S. H.; Tripathi, Sachchida Nand; Verma, Vishal
    Environmental Science & Technology Letters (2020), 7 (7), 504-510CODEN: ESTLCU; ISSN:2328-8930. (American Chemical Society)
    The oxidative potential (OP) of ambient particulate matter (PM) is a metric commonly used to link the aerosol exposure to its adverse health effects. In this study, we report the first-ever real-time measurements of ambient PM2.5 OP based on a dithiothreitol (DTT) assay in Delhi, during a late winter season (Feb. 2019). The chem. compn. of PM was also measured using various collocated online instruments to identify the chem. components driving the PM2.5 OP. The hourly averaged OP during the entire campaign ranged from 0.49 to 3.60 nmol min-1 m-3, with an av. value of 1.57 ± 0.7 nmol min-1 m-3. The secondary org. aerosols appear to be the major driver for the variation in the intrinsic OP of PM2.5. Although the av. PM1 mass concn. at Delhi was 13 times the av. PM2.5 mass concn. reported in Illinois, USA, in a similar study, it was not accompanied by a proportionate increase in the OP (the av. vol.-normalized DTT activity of PM2.5 was only 5 times that reported in Illinois). These findings reveal substantial spatial heterogeneity in the redox properties of PM and highlight the importance of detg. the PM chem. compn. along with its mass concns. for predicting the overall health impacts assocd. with aerosol exposure.
  19. 19
    Kumar, V.; Giannoukos, S.; Haslett, S. L.; Tong, Y.; Singh, A.; Bertrand, A.; Lee, C. P.; Wang, D. S.; Bhattu, D.; Stefenelli, G.; Dave, J. S.; Puthussery, J. V.; Qi, L.; Vats, P.; Rai, P.; Casotto, R.; Satish, R.; Mishra, S.; Pospisilova, V.; Mohr, C.; Bell, D. M.; Ganguly, D.; Verma, V.; Rastogi, N.; Baltensperger, U.; Tripathi, S. N.; Prévôt, A. S. H.; Slowik, J. G. Highly Time-Resolved Chemical Speciation and Source Apportionment of Organic Aerosol Components in Delhi, India, Using Extractive Electrospray Ionization Mass Spectrometry. Atmos. Chem. Phys. 2022, 22, 7739– 7761,  DOI: 10.5194/acp-22-7739-2022
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    Highly time-resolved chemical speciation and source apportionment of organic aerosol components in Delhi, India, using extractive electrospray ionization mass spectrometry
    Kumar, Varun; Giannoukos, Stamatios; Haslett, Sophie L.; Tong, Yandong; Singh, Atinderpal; Bertrand, Amelie; Lee, Chuan Ping; Wang, Dongyu S.; Bhattu, Deepika; Stefenelli, Giulia; Dave, Jay S.; Puthussery, Joseph V.; Qi, Lu; Vats, Pawan; Rai, Pragati; Casotto, Roberto; Satish, Rangu; Mishra, Suneeti; Pospisilova, Veronika; Mohr, Claudia; Bell, David M.; Ganguly, Dilip; Verma, Vishal; Rastogi, Neeraj; Baltensperger, Urs; Tripathi, Sachchida N.; Prevot, Andre S. H.; Slowik, Jay G.
    Atmospheric Chemistry and Physics (2022), 22 (11), 7739-7761CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    In recent years, the Indian capital city of Delhi has been impacted by very high levels of air pollution, esp. during winter. Comprehensive knowledge of the compn. and sources of the org. aerosol (OA), which constitutes a substantial fraction of total particulate mass (PM) in Delhi, is central to formulating effective public health policies. Previous source apportionment studies in Delhi identified key sources of primary OA (POA) and showed that secondary OA (SOA) played a major role but were unable to resolve specific SOA sources. We address the latter through the first field deployment of an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) in Delhi, together with a high-resoln. aerosol mass spectrometer (AMS). Measurements were conducted during the winter of 2018/19, and pos. matrix factorization (PMF) was used sep. on AMS and EESI-TOF datasets to apportion the sources of OA. AMS PMF anal. yielded three primary and two secondary factors which were attributed to hydrocarbon-like OA (HOA), biomass burning OA (BBOA-1 and BBOA-2), more oxidized oxygenated OA (MO-OOA), and less oxidized oxygenated OA (LO-OOA). On av., 40% of the total OA mass was apportioned to the secondary factors. The SOA contribution to total OA mass varied greatly between the daytime (76.8%, 10:00-16:00 local time (LT)) and nighttime (31.0%, 21:00-04:00 LT). The higher chem. resoln. of EESI-TOF data allowed identification of individual SOA sources. The EESI-TOF PMF anal. in total yielded six factors, two of which were primary factors (primary biomass burning and cooking-related OA). The remaining four factors were predominantly of secondary origin: arom. SOA, biogenic SOA, aged biomass burning SOA, and mixed urban SOA. Due to the uncertainties in the EESI-TOF ion sensitivities, mass concns. of EESI-TOF SOA-dominated factors were related to the total AMS SOA (i.e. MO-OOA + LO-OOA) by multiple linear regression (MLR). Arom. SOA was the major SOA component during the daytime, with a 55.2% contribution to total SOA mass (42.4% contribution to total OA). Its contribution to total SOA, however, decreased to 25.4% (7.9% of total OA) during the nighttime. This factor was attributed to the oxidn. of light arom. compds. emitted mostly from traffic. Biogenic SOA accounted for 18.4% of total SOA mass (14.2% of total OA) during the daytime and 36.1% of total SOA mass (11.2% of total OA) during the nighttime. Aged biomass burning and mixed urban SOA accounted for 15.2% and 11.0% of total SOA mass (11.7% and 8.5% of total OA mass), resp., during the daytime and 15.4% and 22.9% of total SOA mass (4.8% and 7.1% of total OA mass), resp., during the nighttime. A simple diln.-partitioning model was applied on all EESI-TOF factors to est. the fraction of obsd. daytime concns. resulting from local photochem. prodn. (SOA) or emissions (POA). Arom. SOA, aged biomass burning, and mixed urban SOA were all found to be dominated by local photochem. prodn., likely from the oxidn. of locally emitted volatile org. compds. (VOCs). In contrast, biogenic SOA was related to the oxidn. of diffuse regional emissions of isoprene and monoterpenes. The findings of this study show that in Delhi, the nighttime high concns. are caused by POA emissions led by traffic and biomass burning and the daytime OA is dominated by SOA, with arom. SOA accounting for the largest fraction. Because arom. SOA is possibly more toxic than biogenic SOA and primary OA, its dominance during the daytime suggests an increased OA toxicity and health-related consequences for the general public.
  20. 20
    Finlayson-Pitts, B. J.; Pitts, J. N. CHAPTER 6 - Rates and Mechanisms of Gas-Phase Reactions in Irradiated Organic – NOx – Air Mixtures. In Chemistry of the Upper and Lower Atmosphere; Finlayson-Pitts, B. J., Pitts, J. N., Eds.; Academic Press: San Diego, 2000, pp 179– 263. DOI: 10.1016/B978-012257060-5/50008-3 .
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    Hallquist, M.; Wenger, J. C.; Baltensperger, U.; Rudich, Y.; Simpson, D.; Claeys, M.; Dommen, J.; Donahue, N. M.; George, C.; Goldstein, A. H.; Hamilton, J. F.; Herrmann, H.; Hoffmann, T.; Iinuma, Y.; Jang, M.; Jenkin, M. E.; Jimenez, J. L.; Kiendler-Scharr, A.; Maenhaut, W.; McFiggans, G.; Mentel, T. F.; Monod, A.; Prévôt, A. S. H.; Seinfeld, J. H.; Surratt, J. D.; Szmigielski, R.; Wildt, J. The Formation, Properties and Impact of Secondary Organic Aerosol: Current and Emerging Issues. Atmos. Chem. Phys. 2009, 9, 5155– 5236,  DOI: 10.5194/acp-9-5155-2009
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    The formation, properties and impact of secondary organic aerosol: current and emerging issues
    Hallquist, M.; Wenger, J. C.; Baltensperger, U.; Rudich, Y.; Simpson, D.; Claeys, M.; Dommen, J.; Donahue, N. M.; George, C.; Goldstein, A. H.; Hamilton, J. F.; Herrmann, H.; Hoffmann, T.; Iinuma, Y.; Jang, M.; Jenkin, M. E.; Jimenez, J. L.; Kiendler-Scharr, A.; Maenhaut, W.; McFiggans, G.; Mentel, Th. F.; Monod, A.; Prevot, A. S. H.; Seinfeld, J. H.; Surratt, J. D.; Szmigielski, R.; Wildt, J.
    Atmospheric Chemistry and Physics (2009), 9 (14/2), 5155-5236CODEN: ACPTCE; ISSN:1680-7316. (Copernicus Publications)
    A review. Secondary org. aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atm. processes, climate and human health. The chem. and phys. processes assocd. with SOA formation are complex and varied, and, despite considerable progress in recent years, a quant. and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atm. science. This review begins with an update on the current state of knowledge on the global SOA budget and is followed by an overview of the atm. degrdn. mechanisms for SOA precursors, gas-particle partitioning theory and the anal. techniques used to det. the chem. compn. of SOA. A survey of recent lab., field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail: mol. characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atm. org. components with sulfuric acid, the chem. and photochem. processing of orgs. in the atm. aq. phase, aerosol formation from real plant emissions, interaction of atm. org. components with water, thermodn. and mixts. in atm. models. Finally, the major challenges ahead in lab., field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.
  22. 22
    Calvert, J. G. The Mechanisms of Atmospheric Oxidation of Aromatic Hydrocarbons; Oxford University Press., 2002.
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    Bianchi, F.; Kurtén, T.; Riva, M.; Mohr, C.; Rissanen, M. P.; Roldin, P.; Berndt, T.; Crounse, J. D.; Wennberg, P. O.; Mentel, T. F.; Wildt, J.; Junninen, H.; Jokinen, T.; Kulmala, M.; Worsnop, D. R.; Thornton, J. A.; Donahue, N.; Kjaergaard, H. G.; Ehn, M. Highly Oxygenated Organic Molecules (HOM) from Gas-Phase Autoxidation Involving Peroxy Radicals: A Key Contributor to Atmospheric Aerosol. Chem. Rev. 2019, 119, 3472– 3509,  DOI: 10.1021/acs.chemrev.8b00395
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    23
    Highly Oxygenated Molecules (HOM) from Gas-Phase Autoxidation Involving Organic Peroxy Radicals: A Key Contributor to Atmospheric Aerosol
    Bianchi, Federico; Kurten, Theo; Riva, Matthieu; Mohr, Claudia; Rissanen, Matti P.; Roldin, Pontus; Berndt, Torsten; Crounse, John D.; Wennberg, Paul O.; Mentel, Thomas F.; Wildt, Jurgen; Junninen, Heikki; Jokinen, Tuija; Kulmala, Markku; Worsnop, Douglas R.; Thornton, Joel A.; Donahue, Neil; Kjaergaard, Henrik G.; Ehn, Mikael
    Chemical Reviews (Washington, DC, United States) (2019), 119 (6), 3472-3509CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review which defines highly oxygenated org. mols. (HOM) formed in the atm. via auto-oxidn. involving peroxy radicals arising from volatile org. compds. describing currently available techniques for their identification/quantification, followed by a summary of the current knowledge on their formation mechanisms and physicochem. properties, is given. Major aims are to provide a common frame for the currently quite fragmented literature on HOM studies and highlighting existing gaps, and suggesting directions for future HOM research. Topics discussed include: introduction; HOM background (defining key concepts, HOM in relation to other classification schemes, historical naming conventions); HOM detection (gas and particle phases, uncertainties and anal. challenges of HOM detection); HOM formation mechanisms (auto-oxidn. involving peroxy radical as HOM source, bimol. RO2 reactions, factors affecting HOM formation); HOM properties and atm. fate (physicochem. properties, removal mechanisms); HOM atm. observations and impact (ambient HOM observation, atm. impact); and summary and perspectives.
  24. 24
    Crounse, J. D.; Nielsen, L. B.; Jørgensen, S.; Kjaergaard, H. G.; Wennberg, P. O. Autoxidation of Organic Compounds in the Atmosphere. J. Phys. Chem. Lett. 2013, 4, 3513– 3520,  DOI: 10.1021/jz4019207
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    24
    Autoxidation of Organic Compounds in the Atmosphere
    Crounse, John D.; Nielsen, Lasse B.; Joergensen, Solvejg; Kjaergaard, Henrik G.; Wennberg, Paul O.
    Journal of Physical Chemistry Letters (2013), 4 (20), 3513-3520CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    A hypothesis that auto-oxidn. (inter- and intra-mol. H abstraction by peroxy radicals) plays an important role in the atm. oxidn. of org. compds., particularly org. matter assocd. with aerosols, is discussed. The rate of this process at room temp. was detd. in the lab. for a model compd., 3-pentanone. Ab-initio calcns. assessed H-shifts within a broader group of substituted org. compds. The rate of H abstraction by peroxy radicals was largely detd. by the thermochem. of nascent alkyl radicals; thus, it was highly affected by neighboring substituents. As a result, auto-oxidn. rates increased rapidly as O-contg. functional groups (carbonyl, hydroxy, hydroperoxy) are added to org. compds. This mechanism was consistent with formation of the multi-functional hydroperoxides and carbonyls often obsd. in atm. aerosol particles.
  25. 25
    Jokinen, T.; Sipilä, M.; Richters, S.; Kerminen, V.-M.; Paasonen, P.; Stratmann, F.; Worsnop, D.; Kulmala, M.; Ehn, M.; Herrmann, H.; Berndt, T. Rapid Autoxidation Forms Highly Oxidized RO2 Radicals in the Atmosphere. Angew. Chem., Int. Ed. 2014, 53, 14596– 14600,  DOI: 10.1002/anie.201408566
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    25
    Rapid Autoxidation Forms Highly Oxidized RO2 Radicals in the Atmosphere
    Jokinen, Tuija; Sipilae, Mikko; Richters, Stefanie; Kerminen, Veli-Matti; Paasonen, Pauli; Stratmann, Frank; Worsnop, Douglas; Kulmala, Markku; Ehn, Mikael; Herrmann, Hartmut; Berndt, Torsten
    Angewandte Chemie, International Edition (2014), 53 (52), 14596-14600CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Gas-phase oxidn. routes of biogenic emissions, mainly isoprene and monoterpenes, in the atm. are still the subject of intensive research with special attention being paid to the formation of aerosol constituents. This lab. study shows that the most abundant monoterpenes (limonene and α-pinene) form highly oxidized RO2 radicals with up to 12 O atoms, along with related closed-shell products, within a few seconds after the initial attack of ozone or OH radicals. The overall process, an intramol. ROO→QOOH reaction and subsequent O2 addn. generating a next R'OO radical, is similar to the well-known autoxidn. processes in the liq. phase (QOOH stands for a hydroperoxyalkyl radical). Field measurements show the relevance of this process to atm. chem. Thus, the well-known reaction principle of autoxidn. is also applicable to the atm. gas-phase oxidn. of hydrocarbons leading to extremely low-volatility products which contribute to org. aerosol mass and hence influence the aerosol-cloud-climate system.
  26. 26
    Molteni, U.; Simon, M.; Heinritzi, M.; Hoyle, C. R.; Bernhammer, A.-K.; Bianchi, F.; Breitenlechner, M.; Brilke, S.; Dias, A.; Duplissy, J.; Frege, C.; Gordon, H.; Heyn, C.; Jokinen, T.; Kürten, A.; Lehtipalo, K.; Makhmutov, V.; Petäjä, T.; Pieber, S. M.; Praplan, A. P.; Schobesberger, S.; Steiner, G.; Stozhkov, Y.; Tomé, A.; Tröstl, J.; Wagner, A. C.; Wagner, R.; Williamson, C.; Yan, C.; Baltensperger, U.; Curtius, J.; Donahue, N. M.; Hansel, A.; Kirkby, J.; Kulmala, M.; Worsnop, D. R.; Dommen, J. Formation of Highly Oxygenated Organic Molecules from α-Pinene Ozonolysis: Chemical Characteristics, Mechanism, and Kinetic Model Development. ACS Earth Space Chem. 2019, 3, 873– 883,  DOI: 10.1021/acsearthspacechem.9b00035
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    26
    Formation of Highly Oxygenated Organic Molecules from α-Pinene Ozonolysis: Chemical Characteristics, Mechanism, and Kinetic Model Development
    Molteni, Ugo; Simon, Mario; Heinritzi, Martin; Hoyle, Christopher R.; Bernhammer, Anne-Kathrin; Bianchi, Federico; Breitenlechner, Martin; Brilke, Sophia; Dias, Antonio; Duplissy, Jonathan; Frege, Carla; Gordon, Hamish; Heyn, Claudia; Jokinen, Tuija; Kurten, Andreas; Lehtipalo, Katrianne; Makhmutov, Vladimir; Petaja, Tuukka; Pieber, Simone M.; Praplan, Arnaud P.; Schobesberger, Siegfried; Steiner, Gerhard; Stozhkov, Yuri; Tome, Antonio; Trostl, Jasmin; Wagner, Andrea C.; Wagner, Robert; Williamson, Christina; Yan, Chao; Baltensperger, Urs; Curtius, Joachim; Donahue, Neil M.; Hansel, Armin; Kirkby, Jasper; Kulmala, Markku; Worsnop, Douglas R.; Dommen, Josef
    ACS Earth and Space Chemistry (2019), 3 (5), 873-883CODEN: AESCCQ; ISSN:2472-3452. (American Chemical Society)
    Terpenes are emitted by vegetation, and their oxidn. in the atm. is an important source of secondary org. aerosol (SOA). A part of this oxidn. can proceed through an autoxidn. process, yielding highly oxygenated org. mols. (HOMs) with low satn. vapor pressure. They can therefore contribute, even in the absence of sulfuric acid, to new particle formation (NPF). The understanding of the autoxidn. mechanism and its kinetics is still far from complete. Here, we present a mechanistic and kinetic anal. of mass spectrometry data from α-pinene (AP) ozonolysis expts. performed during the CLOUD 8 campaign at CERN. We grouped HOMs in classes according to their identified chem. compn. and investigated the relative changes of these groups and their components as a function of the reagent concn. We detd. reaction rate consts. for the different HOM peroxy radical reaction pathways. The accretion reaction between HOM peroxy radicals was found to be extremely fast. We developed a pseudo-mechanism for HOM formation and added it to the AP oxidn. scheme of the Master Chem. Mechanism (MCM). With this extended model, the obsd. concns. and trends in HOM formation were successfully simulated.
  27. 27
    Surratt, J. D.; Chan, A. W. H.; Eddingsaas, N. C.; Chan, M.; Loza, C. L.; Kwan, A. J.; Hersey, S. P.; Flagan, R. C.; Wennberg, P. O.; Seinfeld, J. H. Reactive Intermediates Revealed in Secondary Organic Aerosol Formation from Isoprene. Proc. Natl. Acad. Sci. U.S.A. 2010, 107, 6640– 6645,  DOI: 10.1073/pnas.0911114107
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    Reactive intermediates revealed in secondary organic aerosol formation from isoprene
    Surratt, Jason D.; Chan, Arthur W. H.; Eddingsaas, Nathan C.; Chan, Mannin; Loza, Christine L.; Kwan, Alan J.; Hersey, Scott P.; Flagan, Richard C.; Wennberg, Paul O.; Seinfeld, John H.
    Proceedings of the National Academy of Sciences of the United States of America (2010), 107 (15), 6640-6645, S6640/1-S6640/10CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
    Isoprene is a significant source of atm. org. aerosol; however, the oxidn. pathways that lead to secondary org. aerosol (SOA) have remained elusive. Here, we identify the role of two key reactive intermediates, epoxydiols of isoprene (IEPOX = β-IEPOX + δ-IEPOX) and methacryloylperoxynitrate (MPAN), which are formed during isoprene oxidn. under low- and high-NOx conditions, resp. Isoprene low-NOx SOA is enhanced in the presence of acidified sulfate seed aerosol (mass yield 28.6%) over that in the presence of neutral aerosol (mass yield 1.3%). Increased uptake of IEPOX by acid-catalyzed particle-phase reactions is shown to explain this enhancement. Under high-NOx conditions, isoprene SOA formation occurs through oxidn. of its second-generation product, MPAN. The similarity of the compn. of SOA formed from the photooxidn. of MPAN to that formed from isoprene and methacrolein demonstrates the role of MPAN in the formation of isoprene high-NOx SOA. Reactions of IEPOX and MPAN in the presence of anthropogenic pollutants (i.e., acidic aerosol produced from the oxidn. of SO2 and NO2, resp.) could be a substantial source of "missing urban SOA" not included in current atm. models.
  28. 28
    Pospisilova, V.; Lopez-Hilfiker, F. D.; Bell, D. M.; El Haddad, I.; Mohr, C.; Huang, W.; Heikkinen, L.; Xiao, M.; Dommen, J.; Prevot, A. S. H.; Baltensperger, U.; Slowik, J. G. On the Fate of Oxygenated Organic Molecules in Atmospheric Aerosol Particles. Sci. Adv. 2020, 6(). DOI: 10.1126/sciadv.aax8922 .
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    Bell, D. M.; Wu, C.; Bertrand, A.; Graham, E. L.; Schoonbaert, J.; Giannoukos, S.; Baltensperger, U.; Prevot, A. S. H.; Riipinen, I.; El Haddad, I.; Mohr, C. Particle-phase processing of α-pinene NO3 secondary organic aerosol in the dark. Atmos. Chem. Phys. 2022, 22, 13167– 13182,  DOI: 10.5194/acp-22-13167-2022
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    Particle-phase processing of α-pinene NO3 secondary organic aerosol in the dark
    Bell, David M.; Wu, Cheng; Bertrand, Amelie; Graham, Emelie; Schoonbaert, Janne; Giannoukos, Stamatios; Baltensperger, Urs; Prevot, Andre S. H.; Riipinen, Ilona; El Haddad, Imad; Mohr, Claudia
    Atmospheric Chemistry and Physics (2022), 22 (19), 13167-13182CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    The NO3 radical represents a significant night time oxidant which is present downstream of polluted environments. Existing studies have investigated the formation of secondary org. aerosol (SOA) from NO3 radicals, focusing on the yields, general compn., and hydrolysis of organonitrates; however, there is limited knowledge about how the compn. of NO3-derived SOA evolves as a result of particle-phase reactions. Here, SOA was formed from the reaction of α-pinene with NO3 radicals generated from N2O5, and the resulting SOA was aged in the dark. The initial compn. of NO3-derived α-pinene SOA was slightly dependent upon the concn. of N2O5 injected (excess of NO3 or excess of α-pinene) but was largely dominated by dimer dinitrates (C20H32N2O8-13). Oxidn. reactions (e.g., C20H32N2O8 → C20H32N2O9 → C20H32N2O10) accounted for 60 %-70 % of the particle-phase reactions obsd. Fragmentation reactions and dimer degrdn. pathways made up the remainder of the particle-phase processes occurring. The exact oxidant is not known, although suggestions are offered (e.g., N2O5, org. peroxides, or peroxynitrates). Hydrolysis of -ONO2 functional groups was not an important loss term during dark aging under the relative humidity conditions of our expts. (58 %-62 %), and changes in the bulk organonitrate compn. were likely driven by evapn. of highly nitrogenated mols. Overall, 25 %-30 % of the particle-phase compn. changes as a function of particle-phase reactions during dark aging, representing an important atm. aging pathway.
  30. 30
    Krapf, M.; El Haddad, I.; Bruns, E. A.; Molteni, U.; Daellenbach, K. R.; Prévôt, A. S. H.; Baltensperger, U.; Dommen, J. Labile Peroxides in Secondary Organic Aerosol. Chem 2016, 1, 603– 616,  DOI: 10.1016/j.chempr.2016.09.007
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    Labile Peroxides in Secondary Organic Aerosol
    Krapf, Manuel; El Haddad, Imad; Bruns, Emily A.; Molteni, Ugo; Daellenbach, Kaspar R.; Prevot, Andre S. H.; Baltensperger, Urs; Dommen, Josef
    Chem (2016), 1 (4), 603-616CODEN: CHEMVE; ISSN:2451-9294. (Cell Press)
    Peroxide-contg. highly oxygenated mols. (HOMs) are formed upon ozonolysis of terpenes emitted from the biosphere and are expected to be a major driving force for the formation of new particles and secondary org. aerosol (SOA) in the atm. We evaluate and model the contribution of org. peroxides to α-pinene SOA and their evolution under different conditions. We det. a HOM molar yield of ∼5%, contributing 30% to the initial SOA mass. Although the formation of these compds. is kinetically favored, we demonstrate that they are thermodynamically unstable with half-lives shorter than 1 h under dark conditions. Their decompn. significantly alters SOA chem. compn., volatility, and oxidn. state. We show that photolysis of carbonyls occurring within a timescale of hours is an efficient but largely overlooked mechanism by which SOA may evolve in the atm. Both of these pathways add to a better understanding of the aerosol-climate interaction and the health effects of SOA.
  31. 31
    Zhang, Z.-H.; Hartner, E.; Utinger, B.; Gfeller, B.; Paul, A.; Sklorz, M.; Czech, H.; Yang, B. X.; Su, X. Y.; Jakobi, G.; Orasche, J.; Schnelle-Kreis, J.; Jeong, S.; Gröger, T.; Pardo, M.; Hohaus, T.; Adam, T.; Kiendler-Scharr, A.; Rudich, Y.; Zimmermann, R.; Kalberer, M. Are Reactive Oxygen Species (ROS) a Suitable Metric to Predict Toxicity of Carbonaceous Aerosol Particles?. Atmos. Chem. Phys. 2022, 22, 1793– 1809,  DOI: 10.5194/acp-22-1793-2022
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    Are reactive oxygen species (ROS) a suitable metric to predict toxicity of carbonaceous aerosol particles?
    Zhang, Zhi-Hui; Hartner, Elena; Utinger, Battist; Gfeller, Benjamin; Paul, Andreas; Sklorz, Martin; Czech, Hendryk; Yang, Bin Xia; Su, Xin Yi; Jakobi, Gert; Orasche, Jurgen; Schnelle-Kreis, Jurgen; Jeong, Seongho; Groger, Thomas; Pardo, Michal; Hohaus, Thorsten; Adam, Thomas; Kiendler-Scharr, Astrid; Rudich, Yinon; Zimmermann, Ralf; Kalberer, Markus
    Atmospheric Chemistry and Physics (2022), 22 (3), 1793-1809CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    It is being suggested that particle-bound or particle-induced reactive oxygen species (ROS), which significantly contribute to the oxidative potential (OP) of aerosol particles, are a promising metric linking aerosol compns. to toxicity and adverse health effects. However, accurate ROS quantification remains challenging due to the reactive and short-lived nature of many ROS components and the lack of appropriate anal. methods for a reliable quantification. Consequently, it remains difficult to gauge their impact on human health, esp. to identify how aerosol particle sources and atm. processes drive particle-bound ROS formation in a real-world urban environment. In this study, using a novel online particle-bound ROS instrument (OPROSI), we comprehensively characterized and compared the formation of ROS in secondary org. aerosols (SOAs) generated from org. compds. that represent anthropogenic (naphthalene, SOANAP) and biogenic (β-pinene, SOAβPIN) precursors. The SOA mass was condensed onto soot particles (SP) under varied atmospherically relevant conditions (photochem. aging and humidity) to mimic the SOA formation from a mixing of traffic-related carbonaceous primary aerosols and volatile org. compds. (VOCs). We systematically analyzed the ability of the aq. exts. of the two aerosol types (SOANAP-SP and SOAβPIN-SP) to induce ROS prodn. and OP. We further investigated cytotoxicity and cellular ROS prodn. after exposing human lung epithelial cell cultures (A549) to exts. of the two aerosols. A significant finding of this study is that more than 90% of all ROS components in both SOA types have a short lifetime, highlighting the need to develop online instruments for a meaningful quantification of ROS. Our results also show that photochem. aging promotes particle-bound ROS prodn. and enhances the OP of the aerosols. Compared to SOAβPIN-SP, SOANAP-SP elicited a higher acellular and cellular ROS prodn., a higher OP, and a lower cell viability. These consistent results between chem.-based and biol.-based analyses indicate that particle-bound ROS quantification could be a feasible metric to predict aerosol particle toxicity and adverse human effects. Moreover, the cellular ROS prodn. caused by SOA exposure not only depends on aerosol type but is also affected by exposure dose, highlighting a need to mimic the process of particle deposition onto lung cells and their interactions as realistically as possible to avoid unknown biases.
  32. 32
    Li, Y.; Zhao, J.; Wang, Y.; Seinfeld, J. H.; Zhang, R. Multigeneration Production of Secondary Organic Aerosol from Toluene Photooxidation. Environ. Sci. Technol. 2021, 55, 8592– 8603,  DOI: 10.1021/acs.est.1c02026
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    Multigeneration Production of Secondary Organic Aerosol from Toluene Photooxidation
    Li, Yixin; Zhao, Jiayun; Wang, Yuan; Seinfeld, John H.; Zhang, Renyi
    Environmental Science & Technology (2021), 55 (13), 8592-8603CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Photooxidn. of volatile org. compds. (VOCs) produces secondary org. aerosol (SOA) and light-absorbing brown carbon (BrC) via multiple reaction steps/pathways, reflecting significant chem. complexity relevant to gaseous oxidn. and subsequent gas-to-particle conversion. Toluene is an important VOC under urban conditions, but the fundamental chem. mechanism leading to SOA formation remains uncertain. Here, we elucidate multigeneration SOA prodn. from toluene by simultaneously tracking the evolutions of gas-phase oxidn. and aerosol formation in a reaction chamber. Large size increase and browning of monodisperse sub-micrometer seed particles occur shortly after initiating oxidn. by hydroxyl radical (OH) at 10-90% relative humidity (RH). The evolution in gaseous products and aerosol properties (size/d./optical properties) and chem. speciation of aerosol-phase products indicate that the aerosol growth and browning result from earlier generation products consisting dominantly of dicarbonyl and carboxylic functional groups. While volatile dicarbonyls engage in aq. reactions to yield nonvolatile oligomers and light-absorbing nitrogen heterocycles/heterochains (in the presence of NH3) at high RH, org. acids contribute to aerosol carboxylates via ionic dissocn. or acid-base reaction in a wide RH range. We conclude that toluene contributes importantly to SOA/BrC formation from dicarbonyls and org. acids because of their prompt and high yields from photooxidn. and unique functionalities for participation in aerosol-phase reactions.
  33. 33
    Mutzel, A.; Zhang, Y.; Böge, O.; Rodigast, M.; Kolodziejczyk, A.; Wang, X.; Herrmann, H. Importance of secondary organic aerosol formation of α-pinene, limonene, and m-cresol comparing day- and nighttime radical chemistry. Atmos. Chem. Phys. 2021, 21, 8479– 8498,  DOI: 10.5194/acp-21-8479-2021
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    Importance of secondary organic aerosol formation of α-pinene, limonene, and m-cresol comparing day- and nighttime radical chemistry
    Mutzel, Anke; Zhang, Yanli; Boege, Olaf; Rodigast, Maria; Kolodziejczyk, Agata; Wang, Xinming; Herrmann, Hartmut
    Atmospheric Chemistry and Physics (2021), 21 (11), 8479-8498CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    The oxidn. of biogenic and anthropogenic compds. leads to the formation of secondary org. aerosol mass (SOA). The present study aims to investigate α-pinene, limonene, and m-cresol with regards to their SOA formation potential dependent on relative humidity (RH) under night-(NO3 radicals) and daytime conditions (OH radicals) and the resulting chem. compn. It was found that SOA formation potential of limonene with NO3 under dry conditions significantly exceeds that of the OH-radical reaction, with SOA yields of 15-30%and 10-21%, resp. Addnl., the nocturnal SOA yield was found to be very sensitive towards RH, yielding more SOA under dry conditions. In contrast, the SOA formation potential of α-pinene with NO3 slightly exceeds that of the OH-radical reaction, independent from RH. On av., α-pinene yielded SOA with about 6-7% from NO3 radicals and 3-4% from OH-radical reaction. Surprisingly, unexpectedly high SOA yields were found for m-cresol oxidn. with OH radicals (3-9%), with the highest yield under elevated RH (9%), which is most likely attributable to a higher fraction of 3-methyl-6-nitro-catechol (MNC). While α-pinene and m-cresol SOA was found to be mainly composed of water-sol. compds., 50-68% of nocturnal SOA and 22-39% of daytime limonene SOA are water-insol. The fraction of SOA-bound peroxides which originated from α-pinene varied between 2 and 80% as a function of RH. Furthermore, SOA from α-pinene revealed pinonic acid as the most important particle-phase constituent under day- and nighttime conditions with a fraction of 1-4%. Other compds. detected are norpinonic acid (0.05-1.1% mass fraction), terpenylic acid (0.1-1.1% mass fraction), pinic acid (0.1-1.8% mass fraction), and 3-methyl-1,2,3-tricarboxylic acid (0.05-0.5% mass fraction). All marker compds. showed higher fractions under dry conditions when formed during daytime and showed almost no RH effect when formed during night.
  34. 34
    Zaytsev, A.; Koss, A. R.; Breitenlechner, M.; Krechmer, J. E.; Nihill, K. J.; Lim, C. Y.; Rowe, J. C.; Cox, J. L.; Moss, J.; Roscioli, J. R.; Canagaratna, M. R.; Worsnop, D. R.; Kroll, J. H.; Keutsch, F. N. Mechanistic Study of the Formation of Ring-Retaining and Ring-Opening Products from the Oxidation of Aromatic Compounds under Urban Atmospheric Conditions. Atmos. Chem. Phys. 2019, 19, 15117– 15129,  DOI: 10.5194/acp-19-15117-2019
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    Mechanistic study of the formation of ring-retaining and ring-opening products from the oxidation of aromatic compounds under urban atmospheric conditions
    Zaytsev, Alexander; Koss, Abigail R.; Breitenlechner, Martin; Krechmer, Jordan E.; Nihill, Kevin J.; Lim, Christopher Y.; Rowe, James C.; Cox, Joshua L.; Moss, Joshua; Roscioli, Joseph R.; Canagaratna, Manjula R.; Worsnop, Douglas R.; Kroll, Jesse H.; Keutsch, Frank N.
    Atmospheric Chemistry and Physics (2019), 19 (23), 15117-15129CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Arom. hydrocarbons make up a large fraction of anthropogenic volatile org. compds. and contribute significantly to the prodn. of tropospheric ozone and secondary org. aerosol (SOA). Four toluene and four 1,2,4-trimethylbenzene (1,2,4-TMB) photooxidn. expts. were performed in an environmental chamber under relevant polluted conditions (NOx ∼ 10 ppb). An extensive suite of instrumentation including two proton-transfer-reaction mass spectrometers (PTR-MS) and two chem. ionisation mass spectrometers (NH4+ CIMS and I-CIMS) allowed for quantification of reactive carbon in multiple generations of hydroxyl radical (OH)-initiated oxidn. Oxidn. of both species produces ring-retaining products such as cresols, benzaldehydes, and bicyclic intermediate compds., as well as ring-scission products such as epoxides and dicarbonyls. We report the elemental compn. of these compds. formed under relevant urban high-NO conditions. We show that ring-retaining products for these two precursors are more diverse and abundant than predicted by current mechanisms. We present the speciated elemental compn. of SOA for both precursors and confirm that highly oxygenated products make up a significant fraction of SOA. Ring-scission products are also detected in both the gas and particle phases, and their yields and speciation generally agree with the kinetic model prediction.
  35. 35
    Voliotis, A.; Wang, Y.; Shao, Y.; Du, M.; Bannan, T. J.; Percival, C. J.; Pandis, S. N.; Alfarra, M. R.; McFiggans, G. Exploring the composition and volatility of secondary organic aerosols in mixed anthropogenic and biogenic precursor systems. Atmos. Chem. Phys. 2021, 21, 14251– 14273,  DOI: 10.5194/acp-21-14251-2021
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    Exploring the composition and volatility of secondary organic aerosols in mixed anthropogenic and biogenic precursor systems
    Voliotis, Aristeidis; Wang, Yu; Shao, Yunqi; Du, Mao; Bannan, Thomas J.; Percival, Carl J.; Pandis, Spyros N.; Alfarra, M. Rami; McFiggans, Gordon
    Atmospheric Chemistry and Physics (2021), 21 (18), 14251-14273CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Secondary org. aerosol (SOA) formation from mixts. of volatile precursors may be influenced by the mol. interactions of the components of the mixt. Here, we report measurements of the volatility distribution of SOA formed from the photo-oxidn. of o-cresol, α-pinene, and their mixts., representative anthropogenic and biogenic precursors, in an atm. simulation chamber. The combination of two independent thermal techniques (thermal denuder, TD, and the Filter Inlet for Gases and Aerosols coupled to a high-resoln. time-of-flight chem. ionization mass spectrometer, FIGAERO-CIMS) to measure the particle volatility, along with detailed gas- and particle-phase compn. measurements, provides links between the chem. compn. of the mixt. and the resultant SOA particle volatility. The SOA particle volatility obtained by the two independent techniques showed substantial discrepancies. The particle volatility obtained by the TD was wider, spanning across the LVOC and SVOC range, while the resp. FIGAERO-CIMS derived using two different methods (i.e. calibrated Tmax and partitioning calcns.) was substantially higher (mainly in the SVOC and IVOC, resp.) and narrow. Although the quantification of the SOA particle volatility was challenging, both techniques and methods showed similar trends, with the volatility of the SOA formed from the photo-oxidn. of α-pinene being higher than that measured in the o-cresol system, while the volatility of the SOA particles of the mixt. was between those measured at the single-precursor systems. This behavior could be explained by two opposite effects, the scavenging of the larger mols. with lower volatility produced in the single-precursor expts. that led to an increase in the av. volatility and the formation of unique-to-the-mixt. products that had higher O:C, MW, [Formula Omitted] and, consequently, lower volatility compared to those derived from the individual precursors. We further discuss the potential limitations of FIGAERO-CIMS to report quant. volatilities and their implications for the reported results, and we show that the particle volatility changes can be qual. assessed, while caution should be taken when linking the chem. compn. to the particle volatility. These results present the first detailed observations of SOA particle volatility and compn. in mixed anthropogenic and biogenic systems and provide an anal. context that can be used to explore particle volatility in chamber expts.
  36. 36
    McFiggans, G.; Mentel, T. F.; Wildt, J.; Pullinen, I.; Kang, S.; Kleist, E.; Schmitt, S.; Springer, M.; Tillmann, R.; Wu, C.; Zhao, D.; Hallquist, M.; Faxon, C.; Le Breton, M.; Hallquist, Å. M.; Simpson, D.; Bergström, R.; Jenkin, M. E.; Ehn, M.; Thornton, J. A.; Alfarra, M. R.; Bannan, T. J.; Percival, C. J.; Priestley, M.; Topping, D.; Kiendler-Scharr, A. Secondary Organic Aerosol Reduced by Mixture of Atmospheric Vapours. Nature 2019, 565, 587– 593,  DOI: 10.1038/s41586-018-0871-y
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    Secondary organic aerosol reduced by mixture of atmospheric vapours
    McFiggans, Gordon; Mentel, Thomas F.; Wildt, Jurgen; Pullinen, Iida; Kang, Sungah; Kleist, Einhard; Schmitt, Sebastian; Springer, Monika; Tillmann, Ralf; Wu, Cheng; Zhao, Defeng; Hallquist, Mattias; Faxon, Cameron; Le Breton, Michael; Hallquist, Asa M.; Simpson, David; Bergstrom, Robert; Jenkin, Michael E.; Ehn, Mikael; Thornton, Joel A.; Alfarra, M. Rami; Bannan, Thomas J.; Percival, Carl J.; Priestley, Michael; Topping, David; Kiendler-Scharr, Astrid
    Nature (London, United Kingdom) (2019), 565 (7741), 587-593CODEN: NATUAS; ISSN:0028-0836. (Nature Research)
    Secondary org. aerosol (SOA) contributes to the atm. particulate burden with implications for air quality and climate. Biogenic volatile org. compds. (BVOC), e.g., plant-emitted terpenoids, are important SOA precursors with isoprene dominating BVOC emissions globally; however, the isoprene oxidn. particle mass is generally modest vs. other terpenoids. This work showed isoprene, CO, and CH4 can each suppress the instantaneous mass and overall mass yield derived from monoterpenes in atm. vapor mixts. Isoprene scavenges OH-, preventing their reaction with monoterpenes, and the resulting isoprene peroxy radicals scavenge highly oxygenated monoterpene products. These effects reduce the yield of low volatility products which would otherwise form SOA. Global model calcns. indicated oxidant and product scavenging can operate effectively in the atm. Thus, highly reactive compds. (e.g., isoprene) which produce a modest amt. of aerosol are not necessarily net producers of SOA particle mass and their oxidn. in atm. vapor mixts. can suppress particle no. and SOA mass. SOA atm. formation mechanisms should be considered more realistically to account for mechanistic interactions between products of oxidizing precursor mols. (recognized to be necessary when modeling O3 prodn.).
  37. 37
    Kramer, A. L.; Suski, K. J.; Bell, D. M.; Zelenyuk, A.; Massey Simonich, S. L. Formation of Polycyclic Aromatic Hydrocarbon Oxidation Products in α-Pinene Secondary Organic Aerosol Particles Formed through Ozonolysis. Environ. Sci. Technol. 2019, 53, 6669– 6677,  DOI: 10.1021/acs.est.9b01732
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    Formation of Polycyclic Aromatic Hydrocarbon Oxidation Products in α-Pinene Secondary Organic Aerosol Particles Formed through Ozonolysis
    Kramer, Amber L.; Suski, Kaitlyn J.; Bell, David M.; Zelenyuk, Alla; Massey Simonich, Staci L.
    Environmental Science & Technology (2019), 53 (12), 6669-6677CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Accurate long-range atm. transport (LRAT) modeling of polycyclic arom. hydrocarbons (PAH) and PAH oxidn. products (PAH-OP) in secondary org. aerosol (SOA) particles relies on particle known chem. compn. Four PAH (phenanthrene [PHE] dibenzothiophene [DBT], pyrene [PYR], benz(a)anthracene [BaA]), were studied individually to identify and quantify PAH-OP produced and incorporated into SOA particles formed by ozonolysis of α-pinene in the presence of PAH vapor. SOA particles, characterized by real-time in-situ instrumentation, were collected on quartz fiber filters for off-line PAH and PAH-OP analyses. PAH-OP were measured in all PAH expts. at equal or greater concns. than the individual PAH they were produced from. Total PAH and PAH-OP mass relative to total SOA mass varied for different expts. on individual parent PAH: PHE and 6 quantified PHE-OP (3.0%); DBT and dibenzothiophene sulfone (4.9%); PYR and 3 quantified PYR-OP (3.1%); and BaA and benz(a)anthracene-7,12-dione (0.26%). Further exposure of PAH-SOA to O3 generally increased PAH-OP:PAH concn. ratios, suggesting longer atm. lifetimes for PAH-OP vs. PAH. These data indicated PAH-OP are formed during SOA particle formation and growth.
  38. 38
    Zelenyuk, A.; Imre, D. G.; Wilson, J.; Bell, D. M.; Suski, K. J.; Shrivastava, M.; Beránek, J.; Alexander, M. L.; Kramer, A. L.; Massey Simonich, S. L. The Effect of Gas-Phase Polycyclic Aromatic Hydrocarbons on the Formation and Properties of Biogenic Secondary Organic Aerosol Particles. Faraday Discuss. 2017, 200, 143– 164,  DOI: 10.1039/C7FD00032D
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    The effect of gas-phase polycyclic aromatic hydrocarbons on the formation and properties of biogenic secondary organic aerosol particles
    Zelenyuk, Alla; Imre, Dan G.; Wilson, Jacqueline; Bell, David M.; Suski, Kaitlyn J.; Shrivastava, Manish; Beranek, Josef; Alexander, M. Lizabeth; Kramer, Amber L.; Massey Simonich, Staci L.
    Faraday Discussions (2017), 200 (Atomospheric Chemistry in the Anthropocene), 143-164CODEN: FDISE6; ISSN:1359-6640. (Royal Society of Chemistry)
    When secondary org. aerosol (SOA) particles are formed by ozonolysis in the presence of gas-phase polycyclic arom. hydrocarbons (PAHs), their formation and properties are significantly different from SOA particles formed without PAHs. For all SOA precursors and all PAHs, discussed in this study, the presence of the gas-phase PAHs during SOA formation significantly affects particle mass loadings, compn., growth, evapn. kinetics, and viscosity. SOA particles formed in the presence of PAHs have, as part of their compns., trapped unreacted PAHs and products of heterogeneous reactions between PAHs and ozone. Compared to 'pure' SOA particles, these particles exhibit slower evapn. kinetics, have higher fractions of non-volatile components, like oligomers, and higher viscosities, assuring their longer atm. lifetimes. In turn, the increased viscosity and decreased volatility provide a shield that protects PAHs from chem. degrdn. and evapn., allowing for the long-range transport of these toxic pollutants. The magnitude of the effect of PAHs on SOA formation is surprisingly large. The presence of PAHs during SOA formation increases mass loadings by factors of two to five, and particle no. concns., in some cases, by more than a factor of 100. Increases in SOA mass, particle no. concns., and lifetime have important implications to many atm. processes related to climate, weather, visibility, and human health, all of which relate to the interactions between biogenic SOA and anthropogenic PAHs. The synergistic relationship between SOA and PAHs presented here are clearly complex and call for future research to elucidate further the underlying processes and their exact atm. implications.
  39. 39
    Shrivastava, M.; Cappa, C. D.; Fan, J.; Goldstein, A. H.; Guenther, A. B.; Jimenez, J. L.; Kuang, C.; Laskin, A.; Martin, S. T.; Ng, N. L.; Petaja, T.; Pierce, J. R.; Rasch, P. J.; Roldin, P.; Seinfeld, J. H.; Shilling, J.; Smith, J. N.; Thornton, J. A.; Volkamer, R.; Wang, J.; Worsnop, D. R.; Zaveri, R. A.; Zelenyuk, A.; Zhang, Q. Recent Advances in Understanding Secondary Organic Aerosol: Implications for Global Climate Forcing. Rev. Geophys. 2017, 55, 509– 559,  DOI: 10.1002/2016RG000540
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    Platt, S. M.; El Haddad, I.; Zardini, A. A.; Clairotte, M.; Astorga, C.; Wolf, R.; Slowik, J. G.; Temime-Roussel, B.; Marchand, N.; Ježek, I.; Drinovec, L.; Močnik, G.; Möhler, O.; Richter, R.; Barmet, P.; Bianchi, F.; Baltensperger, U.; Prévôt, A. S. H. Secondary Organic Aerosol Formation from Gasoline Vehicle Emissions in a New Mobile Environmental Reaction Chamber. Atmos. Chem. Phys. 2013, 13, 9141– 9158,  DOI: 10.5194/acp-13-9141-2013
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    Secondary organic aerosol formation from gasoline vehicle emissions in a new mobile environmental reaction chamber
    Platt, S. M.; El Haddad, I.; Zardini, A. A.; Clairotte, M.; Astorga, C.; Wolf, R.; Slowik, J. G.; Temime-Roussel, B.; Marchand, N.; Jezek, I.; Drinovec, L.; Mocnik, G.; Moehler, O.; Richter, R.; Barmet, P.; Bianchi, F.; Baltensperger, U.; Prevot, A. S. H.
    Atmospheric Chemistry and Physics (2013), 13 (18), 9141-9158, 18 pp.CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    We present a new mobile environmental reaction chamber for the simulation of the atm. aging of different emission sources without limitation from the instruments or facilities available at any single site. Photochem. is simulated using a set of 40 UV lights (total power 4 KW). Characterization of the emission spectrum of these lights shows that atm. aging of emissions may be simulated over a range of temps. (-7 to 25 °C). A photolysis rate of NO2, JNO2, of (8.0 ± 0.7) × 10-3 s-1 was detd. at 25°C. We demonstrate the utility of this new system by presenting results on the aging (OH = 12 × 106 cm-3 h) of emissions from a modern (Euro 5) gasoline car operated during a driving cycle (New European Driving Cycle, NEDC) on a chassis dynamometer in a vehicle test cell. Emissions from the entire NEDC were sampled and aged in the chamber. Total org. aerosol (OA; primary org. aerosol (POA) emission + secondary org. aerosol (SOA) formation) was (369.8-397.5) 10-3 g kg-1 fuel, or (13.2-15.4) × 10-3 g km-1, after aging, with aged OA/POA in the range 9-15. A thorough investigation of the compn. of the gas phase emissions suggests that the obsd. SOA is from previously unconsidered precursors and processes. This large enhancement in particulate matter mass from gasoline vehicle aerosol emissions due to SOA formation, if it occurs across a wider range of gasoline vehicles, would have significant implications for our understanding of the contribution of on-road gasoline vehicles to ambient aerosols.
  41. 41
    DeCarlo, P. F.; Kimmel, J. R.; Trimborn, A.; Northway, M. J.; Jayne, J. T.; Aiken, A. C.; Gonin, M.; Fuhrer, K.; Horvath, T.; Docherty, K. S.; Worsnop, D. R.; Jimenez, J. L. Field-Deployable, High-Resolution, Time-of-Flight Aerosol Mass Spectrometer. Anal. Chem. 2006, 78, 8281– 8289,  DOI: 10.1021/ac061249n
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    Field-Deployable, High-Resolution, Time-of-Flight Aerosol Mass Spectrometer
    DeCarlo, Peter F.; Kimmel, Joel R.; Trimborn, Achim; Northway, Megan J.; Jayne, John T.; Aiken, Allison C.; Gonin, Marc; Fuhrer, Katrin; Horvath, Thomas; Docherty, Kenneth S.; Worsnop, Doug R.; Jimenez, Jose L.
    Analytical Chemistry (2006), 78 (24), 8281-8289CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
    Development of a new, high-resoln. time-of-flight aerosol mass spectrometer (HR-ToF-AMS) is reported. High-resoln. capability of this instrument allows direct sepn. of most org. and inorg. ions at the same nominal m/z, quantification of several types of org. fragments (CxHy, CxHyOz, CxHyNp, CxHyOzNp), and direct identification of org. N and organo-S content. This real-time instrument is field-deployable and its high time resoln. (0.5 Hz was demonstrated) makes it well-suited for studies in which time resoln. is crit., e.g., aircraft studies. The instrument has 2 ion optical modes: a single-reflection configuration offering higher sensitivity and lower resolving power (≤∼2100 at m/z 200); and a 2-reflectron configuration yielding higher resolving power (≤∼4300 at m/z 200) with lower sensitivity. It also detns. the size distribution of all ions. One-minute detection limits for sub-micrometer aerosol was <0.04 μg/m3 for all species in high-sensitivity mode and <0.4 μg/m3 in high-resoln. mode. Examples of ambient aerosol data are presented from the SOAR-1 study in Riverside, California, in which ambient org. species spectra were dominated by CxHy and CxHyOz fragments; different org. and inorg. fragments at the same nominal m/z showed different size distributions. Data are also presented from the MIRAGE C-130 aircraft study near Mexico City, Mexico, showing high correlation with independent measurements of surrogate aerosol mass concn.
  42. 42
    Canagaratna, M. R.; Jayne, J. T.; Jimenez, J. L.; Allan, J. D.; Alfarra, M. R.; Zhang, Q.; Onasch, T. B.; Drewnick, F.; Coe, H.; Middlebrook, A.; Delia, A.; Williams, L. R.; Trimborn, A. M.; Northway, M. J.; DeCarlo, P. F.; Kolb, C. E.; Davidovits, P.; Worsnop, D. R. Chemical and Microphysical Characterization of Ambient Aerosols with the Aerodyne Aerosol Mass Spectrometer. Mass Spectrom. Rev. 2007, 26, 185– 222,  DOI: 10.1002/mas.20115
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    Chemical and microphysical characterization of ambient aerosols with the aerodyne aerosol mass spectrometer
    Canagaratna, M. R.; Jayne, J. T.; Jimenez, J. L.; Allan, J. D.; Alfarra, M. R.; Zhang, Q.; Onasch, T. B.; Drewnick, F.; Coe, H.; Middlebrook, A.; Delia, A.; Williams, L. R.; Trimborn, A. M.; Northway, M. J.; DeCarlo, P. F.; Kolb, C. E.; Davidovits, P.; Worsnop, D. R.
    Mass Spectrometry Reviews (2007), 26 (2), 185-222CODEN: MSRVD3; ISSN:0277-7037. (John Wiley & Sons, Inc.)
    A review. The application of mass spectrometric techniques to the real-time measurement and characterization of aerosols represents a significant advance in the field of atm. science. This review focuses on the aerosol mass spectrometer (AMS), an instrument designed and developed at Aerodyne Research, Inc. (ARI) that is the most widely used thermal vaporization AMS. The AMS uses aerodynamic lens inlet technol. together with thermal vaporization and electron-impact mass spectrometry to measure the real-time non-refractory (NR) chem. speciation and mass loading as a function of particle size of fine aerosol particles with aerodynamic diams. between ∼50 and 1,000 nm. The original AMS utilizes a quadrupole mass spectrometer (Q) with electron impact (EI) ionization and produces ensemble av. data of particle properties. Later versions employ time-of-flight (ToF) mass spectrometers and can produce full mass spectral data for single particles. This manuscript presents a detailed discussion of the strengths and limitations of the AMS measurement approach and reviews how the measurements are used to characterize particle properties. Results from selected lab. expts. and field measurement campaigns are also presented to highlight the different applications of this instrument. Recent instrumental developments, such as the incorporation of softer ionization techniques (vacuum UV (VUV) photo-ionization, Li+ ion, and electron attachment) and high-resoln. ToF mass spectrometers, that yield more detailed information about the org. aerosol component are also described.
  43. 43
    Lopez-Hilfiker, F. D.; Pospisilova, V.; Huang, W.; Kalberer, M.; Mohr, C.; Stefenelli, G.; Thornton, J. A.; Baltensperger, U.; Prevot, A. S. H.; Slowik, J. G. An Extractive Electrospray Ionization Time-of-Flight Mass Spectrometer (EESI-TOF) for Online Measurement of Atmospheric Aerosol Particles. Atmos. Meas. Tech. 2019, 12, 4867– 4886,  DOI: 10.5194/amt-12-4867-2019
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    An extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) for online measurement of atmospheric aerosol particles
    Lopez-Hilfiker, Felipe D.; Pospisilova, Veronika; Huang, Wei; Kalberer, Markus; Mohr, Claudia; Stefenelli, Giulia; Thornton, Joel A.; Baltensperger, Urs; Prevot, Andre S. H.; Slowik, Jay G.
    Atmospheric Measurement Techniques (2019), 12 (9), 4867-4886CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
    Real-time, online measurements of atm. org. aerosol (OA) compn. are an essential tool for detg. the emissions sources and physicochem. processes governing aerosol effects on climate and health. Aerosol particles are continuously sampled into the EESI-TOF, where they intersect a spray of charged droplets generated by a conventional electrospray probe. Sol. components are extd. and then ionized as the droplets are evapd. The EESI-TOF achieves a linear response to mass, with detection limits on the order of 1 to 10 ng m-3 in 5 s for typical atmospherically relevant compds. In contrast to conventional electrospray systems, the EESI-TOF response is not significantly affected by a changing OA matrix for the systems investigated. Although the relative sensitivities to a variety of com. available org. stds. vary by more than a factor of 30, the bulk sensitivity to secondary org. aerosol generated from individual precursor gases varies by only a factor of 15. Further, the ratio of compd.-by-compd. sensitivities between the EESI-TOF and an iodide adduct FIGAERO-I-CIMS varies by only ±50%, suggesting that EESI-TOF mass spectra indeed reflect the actual distribution of detectable compds. in the particle phase. Successful deployments of the EESI-TOF for lab. environmental chamber measurements, ground-based ambient sampling, and proof-of-concept measurements aboard a research aircraft highlight the versatility and potential of the EESI-TOF system.
  44. 44
    Wu, C.; Bell, D. M.; Graham, E. L.; Haslett, S.; Riipinen, I.; Baltensperger, U.; Bertrand, A.; Giannoukos, S.; Schoonbaert, J.; El Haddad, I.; Prevot, A. S. H.; Huang, W.; Mohr, C. Photolytically Induced Changes in Composition and Volatility of Biogenic Secondary Organic Aerosol from Nitrate Radical Oxidation during Night-to-Day Transition. Atmos. Chem. Phys. 2021, 21, 14907– 14925,  DOI: 10.5194/acp-21-14907-2021
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    Photolytically induced changes in composition and volatility of biogenic secondary organic aerosol from nitrate radical oxidation during night-to-day transition
    Wu, Cheng; Bell, David M.; Graham, Emelie L.; Haslett, Sophie; Riipinen, Ilona; Baltensperger, Urs; Bertrand, Amelie; Giannoukos, Stamatios; Schoonbaert, Janne; El Haddad, Imad; Prevot, Andre S. H.; Huang, Wei; Mohr, Claudia
    Atmospheric Chemistry and Physics (2021), 21 (19), 14907-14925CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Night-time reactions of biogenic volatile org. compds. (BVOCs) and nitrate radicals (NO3) can lead to the formation of NO3-initiated biogenic secondary org. aerosol (BSOANO3). Here, we study the impacts of light exposure on the chem. compn. and volatility of BSOANO3 formed in the dark from three precursors (isoprene, α-pinene, and β-caryophyllene) in atm. simulation chamber expts. Our study represents BSOANO3 formation conditions where reactions between peroxy radicals (RO2 + RO2) and between RO2 and NO3 are favored. The emphasis here is on the identification of particle-phase organonitrates (ONs) formed in the dark and their changes during photolytic ageing on timescales of ~ 1 h. The chem. compn. of particle-phase compds. was measured with a chem. ionization mass spectrometer with a filter inlet for gases and aerosols (FIGAERO-CIMS) and an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF). Volatility information on BSOANO3 was derived from FIGAERO-CIMS desorption profiles (thermograms) and a volatility tandem differential mobility analyzer (VTDMA). During photolytic ageing, there was a relatively small change in mass due to evapn. (< 5% for the isoprene and α-pinene BSOANO3, and 12% for the β-caryophyllene BSOANO3), but we obsd. significant changes in the chem. compn. of the BSOANO3. Overall, 48%, 44%, and 60% of the resp. total signal for the isoprene, α-pinene, and β-caryophyllene BSOANO3 was sensitive to photolytic ageing and exhibited decay. The photolabile compds. include both monomers and oligomers. Oligomers can decomp. into their monomer units through photolysis of the bonds (e.g. likely O-O) between them. Fragmentation of both oligomers and monomers also happened at other positions, causing the formation of compds. with shorter carbon skeletons. The cleavage of the nitrate functional group from the carbon chain was likely not a main degrdn. pathway in our expts. In addn., photolytic degrdn. of compds. changes their volatility and can lead to evapn. We use different methods to assess bulk volatilities and discuss their changes during both dark ageing and photolysis in the context of the chem. changes that we obsd. We also reveal large uncertainties in satn. vapor pressure estd. from parameterizations for the ON oligomers with multiple nitrate groups. Overall, our results suggest that photolysis causes photodegrdn. of a substantial fraction of BSOANO3, changes both the chem. compn. and the bulk volatility of the particles, and might be a potentially important loss pathway of BSOANO3 during the night-to-day transition.
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    Wolfe, G. M.; Marvin, M. R.; Roberts, S. J.; Travis, K. R.; Liao, J. The Framework for 0-D Atmospheric Modeling (F0AM) v3.1. Geosci. Model Dev. 2016, 9, 3309– 3319,  DOI: 10.5194/gmd-9-3309-2016
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    Saunders, S. M.; Jenkin, M. E.; Derwent, R. G.; Pilling, M. J. Protocol for the Development of the Master Chemical Mechanism, MCM v3 (Part A): Tropospheric Degradation of Non-Aromatic Volatile Organic Compounds. Atmos. Chem. Phys. 2003, 3, 161– 180,  DOI: 10.5194/acp-3-161-2003
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    Protocol for the development of the master chemical mechanism, MCM v3 (part A): tropospheric degradation of non-aromatic volatile organic compounds
    Saunders, S. M.; Jenkin, M. E.; Derwent, R. G.; Pilling, M. J.
    Atmospheric Chemistry and Physics (2003), 3 (1), 161-180CODEN: ACPTCE; ISSN:1680-7324. (European Geophysical Society)
    Kinetic and mechanistic data relevant to the tropospheric degrdn. of volatile org. compds. (VOC), and the prodn. of secondary pollutants, were previously used to define a protocol which underpinned the construction of a near-explicit Master Chem. Mechanism. An update to the previous protocol is presented, which was used to define degrdn. schemes for 107 nonarom. VOC as part of version 3 of the Master Chem. Mechanism (MCM v3). The treatment of 18 arom. VOC is described in a companion paper. The protocol is divided into subsections describing initiation reactions, the reactions of the radical intermediates and the further degrdn. of 1st and subsequent generation products. Emphasis is placed on updating the previous information, and outlining the methodol. which is specifically applicable to VOC not considered previously (e.g., α- and β-pinene). The present protocol aims to take into consideration work available in the open literature up to the beginning of 2001, and some other studies known by the authors which were under review at the time. Application of MCM v3 in appropriate box models indicates that the representation of isoprene degrdn. provides a good description of the speciated distribution of oxygenated org. products obsd. in reported field studies where isoprene was the dominant emitted hydrocarbon, and that the α-pinene degrdn. chem. provides a good description of the time dependence of key gas phase species in α-pinene/NOX photooxidn. expts. carried out in the European Photoreactor (EUPHORE). Photochem. Ozone Creation Potentials (POCP) were calcd. for the 106 non-arom. non-methane VOC in MCM v3 for idealized conditions appropriate to north-west Europe, using a photochem. trajectory model. The POCP values provide a measure of the relative ozone forming abilities of the VOC. Where applicable, the values are compared with those calcd. with previous versions of the MCM.
  47. 47
    Jenkin, M. E.; Saunders, S. M.; Pilling, M. J. The Tropospheric Degradation of Volatile Organic Compounds: A Protocol for Mechanism Development. Atmos. Environ. 1997, 31, 81– 104,  DOI: 10.1016/S1352-2310(96)00105-7
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    The tropospheric degradation of volatile organic compounds: a protocol for mechanism development
    Jenkin, Michael E.; Saunders, Sandra M.; Pilling, Michael J.
    Atmospheric Environment (1996), 31 (1), 81-104CODEN: AENVEQ; ISSN:1352-2310. (Elsevier)
    Kinetic and mechanistic data relevant to the tropospheric oxidn. of volatile org. compds. (VOCs) were used to define a series of rules for the construction of detailed degrdn. schemes for use in numerical models. These rules are intended to apply to the treatment of a wide range of non-arom. hydrocarbons and oxygenated and chlorinated VOCs, and are currently used to provide an up-to-date mechanism describing the degrdn. of a range of VOCs, and the formation of secondary oxidants, for use in a model of the boundary layer over Europe. The schemes constructed using this protocol are applicable, however, to a wide range of ambient conditions, and may be employed in models of urban, rural, or remote tropospheric environments, or for the simulation of secondary pollutant formation for a range of NOx or VOC emission scenarios. These schemes are believed to be particularly appropriate for comparative assessments of the formation of oxidants, such as ozone, from the degrdn. of org. compds. The protocol is divided into a series of subsections dealing with initiation reactions, the reactions of the radical intermediates and the further degrdn. of first and subsequent generation products. The present work draws heavily on previous reviews and evaluations of data relevant to tropospheric chem. Where necessary, however, existing recommendations are adapted, or new rules are defined, to reflect recent improvements in the database, particularly with regard to the treatment of peroxy radical (RO2) reactions for which there have been major advances, even since comparatively recent reviews. The present protocol aims to take into consideration work available in the open literature up to the end of 1994, and some further studies known by the authors, which were under review at that time. A major disadvantage of explicit chem. mechanisms is the very large no. of reactions potentially generated, if a series of rules is rigorously applied. The protocol aims to limit the no. of reactions in a degrdn. scheme by applying a degree of strategic simplication, while maintaining the essential features of the chem. These simplication measures are described, and their influence is demonstrated and discussed. The resultant mechanisms are believed to provide a suitable starting point for the generation of reduced chem. mechanisms.
  48. 48
    Mellouki, A.; Ammann, M.; Cox, R. A.; Crowley, J. N.; Herrmann, H.; Jenkin, M. E.; Mcneill, V. F.; Troe, J.; Wallington, T. J. Evaluated Kinetic and Photochemical Photochemical Data for Atmospheric Chemistry: Volume VIII - Gas-Phase Reactions of Organic Species with Four, or More, Carbon Atoms (≥ C4). Atmos. Chem. Phys. 2021, 21, 4797– 4808,  DOI: 10.5194/acp-21-4797-2021
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    Evaluated kinetic and photochemical data for atmospheric chemistry: volume VIII - gas-phase reactions of organic species with four, or more, carbon atoms (≥ C4)
    Mellouki, Abdelwahid; Ammann, Markus; Cox, R. Anthony; Crowley, John N.; Herrmann, Hartmut; Jenkin, Michael E.; McNeill, V. Faye; Troe, Jurgen; Wallington, Timothy J.
    Atmospheric Chemistry and Physics (2021), 21 (6), 4797-4808CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    This article, the eighth in the series, presents kinetic and photochem. data sheets evaluated by the IUPAC Task Group on Atm. Chem. Kinetic Data Evaluation. It covers the gas phase thermal and photochem. reactions of org. species with four, or more, carbon atoms (C4) available on the IUPAC website in 2021, including thermal reactions of closed-shell org. species with HO and NO3 radicals and their photolysis. The present work is a continuation of vol. II, with new reactions and updated data sheets for reactions of HO (77 reactions) and NO3 (36 reactions) with C4 orgs., including alkanes, alkenes, dienes, aroms., oxygenated, org. nitrates and nitro compds. in addn. to photochem. processes for nine species. The article consists of a summary table, contg. the recommended kinetic parameters for the evaluated reactions, and a supplement contg. the data sheets, which provide information upon which recommendations are made.
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    Jenkin, M. E.; Valorso, R.; Aumont, B.; Rickard, A. R.; Wallington, T. J. Estimation of Rate Coefficients and Branching Ratios for Gas-Phase Reactions of OH with Aromatic Organic Compounds for Use in Automated Mechanism Construction. Atmos. Chem. Phys. 2018, 18, 9329– 9349,  DOI: 10.5194/acp-18-9329-2018
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    Estimation of rate coefficients and branching ratios for gas-phase reactions of OH with aromatic organic compounds for use in automated mechanism construction
    Jenkin, Michael E.; Valorso, Richard; Aumont, Bernard; Rickard, Andrew R.; Wallington, Timothy J.
    Atmospheric Chemistry and Physics (2018), 18 (13), 9329-9349CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Reaction with the hydroxyl (OH) radical is the dominant removal process for volatile org. compds. (VOCs) in the atm. Rate coeffs. for the reactions of OH with VOCs are therefore essential parameters for chem. mechanisms used in chem. transport models, and are required more generally for impact assessments involving estn. of atm. lifetimes or oxidn. rates for VOCs. A structure-activity relationship (SAR) method is presented for the reactions of OH with arom. org. compds., with the reactions of aliph. org. compds. considered in the preceding companion paper. The SAR is optimized using a preferred set of data including reactions of OH with 67 monocyclic arom. hydrocarbons and oxygenated org. compds. In each case, the rate coeff. is defined in terms of a summation of partial rate coeffs. for H abstraction or OH addn. at each relevant site in the given org. compd., so that the attack distribution is defined. The SAR can therefore guide the representation of the OH reactions in the next generation of explicit detailed chem. mechanisms. Rules governing the representation of the reactions of the product radicals under tropospheric conditions are also summarized, specifically the rapid reaction sequences initiated by their reactions with O2.
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    Barmet, P.; Dommen, J.; DeCarlo, P. F.; Tritscher, T.; Praplan, A. P.; Platt, S. M.; Prévôt, A. S. H.; Donahue, N. M.; Baltensperger, U. OH clock determination by proton transfer reaction mass spectrometry at an environmental chamber. Atmos. Meas. Tech. 2012, 5, 647– 656,  DOI: 10.5194/amt-5-647-2012
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    OH clock determination by proton transfer reaction mass spectrometry at an environmental chamber
    Barmet, P.; Dommen, J.; DeCarlo, P. F.; Tritscher, T.; Praplan, A. P.; Platt, S. M.; Prevot, A. S. H.; Donahue, N. M.; Baltensperger, U.
    Atmospheric Measurement Techniques (2012), 5 (3), 647-656CODEN: AMTTC2; ISSN:1867-1381. (Copernicus Publications)
    The hydroxyl free radical (OH) is the major oxidizing species in the lower atm. Measuring the OH concn. is generally difficult and involves elaborate, expensive, custom-made exptl. setups. Thus other more economical techniques, capable of detg. OH concns. at environmental chambers, would be valuable. This work is based on an indirect method of OH concn. measurement, by monitoring an appropriate OH tracer by proton transfer reaction mass spectrometry (PTR-MS). 3-Pentanol, 3-pentanone and pinonaldehyde (PA) were used as OH tracers in α-pinene (AP) secondary org. aerosol (SOA) aging studies. In addn. we tested butanol-d9 as a potential "universal" OH tracer and detd. its reaction rate const. with OH: kbutanol-d9 = 3-4(±0.88) × 10-12 cm3 mol.-1 s-1. In order to make the chamber studies more comparable among each other as well as to atm. measurements we suggest the use of a chem. (time) dimension: the OH clock, which corresponds to the integrated OH concn. over time.
  51. 51
    Thomsen, D.; Thomsen, L. D.; Iversen, E. M.; Björgvinsdóttir, T. N.; Vinther, S. F.; Skønager, J. T.; Hoffmann, T.; Elm, J.; Bilde, M.; Glasius, M. Ozonolysis of α-Pinene and Δ3-Carene Mixtures: Formation of Dimers with Two Precursors. Environ. Sci. Technol. 2022, 56, 16643– 16651,  DOI: 10.1021/acs.est.2c04786
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    Ozonolysis of α-Pinene and Δ3-Carene Mixtures: Formation of Dimers with Two Precursors
    Thomsen, Ditte; Thomsen, Lotte Dyrholm; Iversen, Emil Mark; Bjorgvinsdottir, Thuridjur Nott; Vinther, Sofie Falk; Skoenager, Jane Tygesen; Hoffmann, Thorsten; Elm, Jonas; Bilde, Merete; Glasius, Marianne
    Environmental Science & Technology (2022), 56 (23), 16643-16651CODEN: ESTHAG; ISSN:1520-5851. (American Chemical Society)
    The formation of secondary org. aerosol (SOA) from the structurally similar monoterpenes, α-pinene and Δ3-carene, differs substantially. The aerosol phase is already complex for a single precursor, and when mixts. are oxidized, products, e.g., dimers, may form between different volatile org. compds. (VOCs). This work investigates whether differences in SOA formation and properties from the oxidn. of individual monoterpenes persist when a mixt. of the monoterpenes is oxidized. Ozonolysis of α-pinene, Δ3-carene, and a 1:1 mixt. of them was performed in the Aarhus University Research on Aerosol (AURA) atm. simulation chamber. Here, ~ 100 ppb of monoterpene was oxidized by 200 ppb O3 under dark conditions at 20°C. The particle no. concn. and particle mass concn. for ozonolysis of α-pinene exceed those from ozonolysis of Δ3-carene alone, while their mixt. results in concns. similar to α-pinene ozonolysis. Detailed offline anal. reveals evidence of VOC-cross-product dimers in SOA from ozonolysis of the monoterpene mixt.: a VOC-cross-product dimer likely composed of the monomeric units cis-caric acid and 10-hydroxy-pinonic acid and a VOC-cross-product dimer ester likely from the monomeric units caronaldehyde and terpenylic acid were tentatively identified by liq. chromatog.-mass spectrometry. To improve the understanding of chem. mechanisms detg. SOA, it is relevant to identify VOC-cross-products.
  52. 52
    Bell, D. M.; Pospisilova, V.; Lopez-Hilfiker, F.; Bertrand, A.; Xiao, M.; Zhou, X.; Huang, W.; Wang, D. S.; Lee, C. P.; Dommen, J.; Baltensperger, U.; Prevot, A. S. H.; El Haddad, I.; Slowik, J. G. Effect of OH scavengers on the chemical composition of α-pinene secondary organic aerosol. Environ. Sci.: Atmos. 2023, 3, 115– 123,  DOI: 10.1039/D2EA00105E
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    Effect of OH scavengers on the chemical composition of α-pinene secondary organic aerosol
    Bell, David M.; Pospisilova, Veronika; Lopez-Hilfiker, Felipe; Bertrand, Amelie; Xiao, Mao; Zhou, Xueqin; Huang, Wei; Wang, Dongyu S.; Lee, Chuan Ping; Dommen, Josef; Baltensperger, Urs; Prevot, Andre S. H.; El Haddad, Imad; Slowik, Jay G.
    Environmental Science: Atmospheres (2023), 3 (1), 115-123CODEN: ESANC9; ISSN:2634-3606. (Royal Society of Chemistry)
    OH scavengers are extensively used in studies of secondary org. aerosol (SOA) because they create an idealized environment where only a single oxidn. pathway is occurring. Here, we present a detailed mol. characterization of SOA produced from α-pinene + O3 with a variety of OH scavengers using the extractive electrospray time-of-flight mass spectrometer in our atm. simulation chamber, which is complemented by characterizing the gas phase compn. in flow reactor expts. Under our exptl. conditions, radical chem. largely controls the compn. of SOA. Besides playing their desired role in suppressing the reaction of α-pinene with OH, OH scavengers alter the reaction pathways of radicals produced from α-pinene + O3. This involves changing the HO2 : RO2 ratio, the identity of the RO2 radicals present, and the RO2 major sinks. As a result, the use of the OH scavengers has significant effects on the compn. of SOA, including inclusions of scavenger mols. in SOA, the promotion of fragmentation reactions, and depletion of dimers formed via α-pinene RO2-RO2 reactions. To date fragmentation reactions and inclusion of OH scavenger products into secondary org. aerosol have not been reported in atm. simulation chamber studies. Therefore, care should be considered if and when to use an OH scavenger during expts.
  53. 53
    Berndt, T.; Richters, S.; Jokinen, T.; Hyttinen, N.; Kurtén, T.; Otkjær, R. V.; Kjaergaard, H. G.; Stratmann, F.; Herrmann, H.; Sipilä, M.; Kulmala, M.; Ehn, M. Hydroxyl Radical-Induced Formation of Highly Oxidized Organic Compounds. Nat. Commun. 2016, 7, 13677,  DOI: 10.1038/ncomms13677
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    Hydroxyl radical-induced formation of highly oxidized organic compounds
    Berndt, Torsten; Richters, Stefanie; Jokinen, Tuija; Hyttinen, Noora; Kurten, Theo; Otkjaer, Rasmus V.; Kjaergaard, Henrik G.; Stratmann, Frank; Herrmann, Hartmut; Sipilae, Mikko; Kulmala, Markku; Ehn, Mikael
    Nature Communications (2016), 7 (), 13677CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
    Explaining the formation of secondary org. aerosol is an intriguing question in atm. sciences because of its importance for Earth's radiation budget and the assocd. effects on health and ecosystems. A breakthrough was recently achieved in the understanding of secondary org. aerosol formation from ozone reactions of biogenic emissions by the rapid formation of highly oxidized multifunctional org. compds. via autoxidn. However, the important daytime hydroxyl radical reactions have been considered to be less important in this process. Here we report measurements on the reaction of hydroxyl radicals with α- and β-pinene applying improved mass spectrometric methods. Our lab. results prove that the formation of highly oxidized products from hydroxyl radical reactions proceeds with considerably higher yields than previously reported. Field measurements support these findings. Our results allow for a better description of the diurnal behavior of the highly oxidized product formation and subsequent secondary org. aerosol formation in the atm.
  54. 54
    Ehn, M.; Thornton, J. A.; Kleist, E.; Sipilä, M.; Junninen, H.; Pullinen, I.; Springer, M.; Rubach, F.; Tillmann, R.; Lee, B.; Lopez-Hilfiker, F.; Andres, S.; Acir, I.-H.; Rissanen, M.; Jokinen, T.; Schobesberger, S.; Kangasluoma, J.; Kontkanen, J.; Nieminen, T.; Kurtén, T.; Nielsen, L. B.; Jørgensen, S.; Kjaergaard, H. G.; Canagaratna, M.; Maso, M. D.; Berndt, T.; Petäjä, T.; Wahner, A.; Kerminen, V.-M.; Kulmala, M.; Worsnop, D. R.; Wildt, J.; Mentel, T. F. A Large Source of Low-Volatility Secondary Organic Aerosol. Nature 2014, 506, 476– 479,  DOI: 10.1038/nature13032
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    A large source of low-volatility secondary organic aerosol
    Ehn, Mikael; Thornton, Joel A.; Kleist, Einhard; Sipilae, Mikko; Junninen, Heikki; Pullinen, Iida; Springer, Monika; Rubach, Florian; Tillmann, Ralf; Lee, Ben; Lopez-Hilfiker, Felipe; Andres, Stefanie; Acir, Ismail-Hakki; Rissanen, Matti; Jokinen, Tuija; Schobesberger, Siegfried; Kangasluoma, Juha; Kontkanen, Jenni; Nieminen, Tuomo; Kurten, Theo; Nielsen, Lasse B.; Jorgensen, Solvejg; Kjaergaard, Henrik G.; Canagaratna, Manjula; Dal Maso, Miikka; Berndt, Torsten; Petaejae, Tuukka; Wahner, Andreas; Kerminen, Veli-Matti; Kulmala, Markku; Worsnop, Douglas R.; Wildt, Juergen; Mentel, Thomas F.
    Nature (London, United Kingdom) (2014), 506 (7489), 476-479CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
    Forests emit large quantities of volatile org. compds. (VOC) to the atm. Their condensable oxidn. products can form secondary org. aerosols (SOA), a significant, ubiquitous component of atm. aerosol known to affect the Earth radiation balance by scattering solar radiation and acting as cloud condensation nuclei. A quant. assessment of such climate effects is hampered by several factors, including an incomplete understanding of how biogenic VOC contribute to formation of atm. SOA. Growth of newly formed particle sizes from <3 nm to cloud condensation nuclei (∼100 nm) in many continental ecosystems requires abundant, essentially non-volatile org. vapor, but sources and compns. of such vapors are unknown. This work examd. oxidn. of VOC, particularly the terpene, α-pinene, under atmospherically relevant conditions in chamber expts. A direct pathway leads from several biogenic VOC, e.g., monoterpenes, to formation of large amts. of extremely low-volatility vapors. These vapors form at significant mass yields in the gas phase and condense irreversibly onto aerosol surfaces producing SOA, helping to explain the discrepancy between the obsd. atm. burden of SOA and that reported in many model studies. Results further demonstrated how these low-volatility vapors can enhance or even dominate, aerosol formation and growth over forested regions, providing a missing link between biogenic VOC and their conversion to aerosol particles. Results could help improve biosphere-aerosol-climate feedback mechanism assessments, and biogenic emissions/air quality and climate effects generally.
  55. 55
    Kristensen, K.; Watne, Å. K.; Hammes, J.; Lutz, A.; Petäjä, T.; Hallquist, M.; Bilde, M.; Glasius, M. High-Molecular Weight Dimer Esters Are Major Products in Aerosols from α-Pinene Ozonolysis and the Boreal Forest. Environ. Sci. Technol. Lett. 2016, 3, 280– 285,  DOI: 10.1021/acs.estlett.6b00152
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    High-Molecular Weight Dimer Esters Are Major Products in Aerosols from α-Pinene Ozonolysis and the Boreal Forest
    Kristensen, Kasper; Watne, Aagot K.; Hammes, Julia; Lutz, Anna; Petaja, Tuukka; Hallquist, Mattias; Bilde, Merete; Glasius, Marianne
    Environmental Science & Technology Letters (2016), 3 (8), 280-285CODEN: ESTLCU; ISSN:2328-8930. (American Chemical Society)
    This study studies the contribution of high-mol. wt. dimer esters to lab.-generated α-pinene gas- and particle-phase secondary org. aerosol (SOA) and particulate matter (PM) collected at the Nordic boreal forest site in Finland. Lab. flow reactor expts. (25°) show that dimer esters from ozonolysis of α-pinene contribute between 5 and 16% of the freshly formed α-pinene particle-phase SOA mass. An increased level of formation is obsd. at a higher relative humidity of ∼40%, and the presence of a hydroxyl radical (OH) scavenger is shown to affect the formation of dimer esters. Of the 28 dimer esters identified in lab. α-pinene SOA, 15 are also obsd. in ambient PM samples, contributing between 0.5 and 1.6% of the total PM1. The obsd. esters show good correlation with known α-pinene SOA tracers in collected PM samples. This work reveals an, until now, unrecognized contribution of dimer esters from α-pinene oxidn. to boreal forest PM.
  56. 56
    Zhang, X.; McVay, R. C.; Huang, D. D.; Dalleska, N. F.; Aumont, B.; Flagan, R. C.; Seinfeld, J. H. Formation and evolution of molecular products in α-pinene secondary organic aerosol. Proc. Natl. Acad. Sci. U.S.A. 2015, 112, 14168– 14173,  DOI: 10.1073/pnas.1517742112
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    Formation and evolution of molecular products in α-pinene secondary organic aerosol
    Zhang, Xuan; McVay, Renee C.; Huang, Dan D.; Dalleska, Nathan F.; Aumont, Bernard; Flagan, Richard C.; Seinfeld, John H.
    Proceedings of the National Academy of Sciences of the United States of America (2015), 112 (46), 14168-14173CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
    Much of the understanding of atm. secondary org. aerosol (SOA) formation from volatile org. compds. is from lab. chamber measurements, including mass yield and elemental compn. These measurements alone are insufficient to identify chem. mechanisms for SOA prodn. A comprehensive dataset on the mol. identity, abundance, and kinetics of α-pinene SOA, a canonical system which received much attention due to its importance as an org. aerosol source in the pristine atm., is presented. Identified org. species accounted for ∼58-72% of the α-pinene SOA mass and were characterized as semi-volatile/low-volatility monomers and extremely low volatility dimers, which exhibited comparable oxidn. states yet different functionalities. For the first time, the α-pinene SOA formation process features are revealed from the dynamics of individual particle-phase components. Although monomeric products dominate the overall aerosol mass, rapid prodn. of dimers plays a key role in initiating particle growth. Continuous monomer prodn. is obsd. after the parent (α-pinene) is consumed, which cannot be explained solely by gas-phase photochem. prodn. Also, distinct monomer and dimer responses to α-pinene oxidn. by O3 vs. OH-, temp., and relative humidity were obsd. Gas-phase radical combination reactions in conjunction with labile mol. condensed phase rearrangement potentially explain the newly characterized SOA features and open up further avenues to understand α-pinene SOA formation and evolution mechanisms.
  57. 57
    Wang, D. S.; Lee, C. P.; Krechmer, J. E.; Majluf, F.; Tong, Y.; Canagaratna, M. R.; Schmale, J.; Prévôt, A. S. H.; Baltensperger, U.; Dommen, J.; El Haddad, I.; Slowik, J. G.; Bell, D. M. Constraining the Response Factors of an Extractive Electrospray Ionization Mass Spectrometer for Near-Molecular Aerosol Speciation. Atmos. Meas. Tech. 2021, 14, 6955– 6972,  DOI: 10.5194/amt-14-6955-2021
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    Constraining the response factors of an extractive electrospray ionization mass spectrometer for near-molecular aerosol speciation
    Wang, Dongyu S.; Lee, Chuan Ping; Krechmer, Jordan E.; Majluf, Francesca; Tong, Yandong; Canagaratna, Manjula R.; Schmale, Julia; Prevot, Andre S. H.; Baltensperger, Urs; Dommen, Josef; El Haddad, Imad; Slowik, Jay G.; Bell, David M.
    Atmospheric Measurement Techniques (2021), 14 (11), 6955-6972CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
    Online characterization of aerosol compn. at the near-mol. level is key to understanding chem. reaction mechanisms, kinetics, and sources under various atm. conditions. The recently developed extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) is capable of detecting a wide range of org. oxidn. products in the particle phase in real time with minimal fragmentation. Quantification can sometimes be hindered by a lack of available com. stds. for aerosol constituents, however. Good correlations between the EESI-TOF and other aerosol speciation techniques have been reported, though no attempts have yet been made to parameterize the EESI-TOF response factor for different chem. species. Here, we report the first parameterization of the EESI-TOF response factor for secondary org. aerosol (SOA) at the near-mol. level based on its elemental compn. SOA was formed by ozonolysis of monoterpene or OH oxidn. of aroms. inside an oxidn. flow reactor (OFR) using ammonium nitrate as seed particles. A Vocus proton-transfer reaction mass spectrometer (Vocus-PTR) and a high-resoln. aerosol mass spectrometer (AMS) were used to det. the gas-phase mol. compn. and the particle-phase bulk chem. compn., resp. The EESI response factors towards bulk SOA coating and the inorg. seed particle core were constrained by intercomparison with the AMS. The highest bulk EESI response factor was obsd. for SOA produced from 1,3,5-trimethylbenzene, followed by those produced from d-limonene and o-cresol, consistent with previous findings. The near-mol. EESI response factors were derived from intercomparisons with VocusPTR measurements and were found to vary from 103 to 106 ion counts s-1 ppb-1, mostly within ±1 order of magnitude of their geometric mean of 104.6 ion counts s-1 ppb-1. For arom. SOA components, the EESI response factors correlated with mol. wt. and oxygen content and inversely correlated with volatility. The near-mol. response factors mostly agreed within a factor of 20 for isomers obsd. across the aroms. and biogenic systems. Parameterization of the near-mol. response factors based on the measured elemental formulas could reproduce the empirically detd. response factor for a single volatile org. compd. (VOC) system to within a factor of 5 for the configuration of our mass spectrometers. The results demonstrate that std.-free quantification using the EESI-TOF is possible.
  58. 58
    Canagaratna, M. R.; Jimenez, J. L.; Kroll, J. H.; Chen, Q.; Kessler, S. H.; Massoli, P.; Hildebrandt Ruiz, L.; Fortner, E.; Williams, L. R.; Wilson, K. R.; Surratt, J. D.; Donahue, N. M.; Jayne, J. T.; Worsnop, D. R. Elemental Ratio Measurements of Organic Compounds Using Aerosol Mass Spectrometry: Characterization, Improved Calibration, and Implications. Atmos. Chem. Phys. 2015, 15, 253– 272,  DOI: 10.5194/acp-15-253-2015
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    Elemental ratio measurements of organic compounds using aerosol mass spectrometry: characterization, improved calibration, and implications
    Canagaratna, M. R.; Jimenez, J. L.; Kroll, J. H.; Chen, Q.; Kessler, S. H.; Massoli, P.; Hildebrandt Ruiz, L.; Fortner, E.; Williams, L. R.; Wilson, K. R.; Surratt, J. D.; Donahue, N. M.; Jayne, J. T.; Worsnop, D. R.
    Atmospheric Chemistry and Physics (2015), 15 (1), 253-272/1-253-272/20, 20 pp.CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Elemental compns. of org. aerosol (OA) particles provide useful constraints on OA sources, chem. evolution, and effects. The Aerodyne high-resoln. time-of-flight aerosol mass spectrometer (HR-ToF-AMS) is widely used to measure OA elemental compn. This study evaluates AMS measurements of at. oxygen-to-carbon (O : C), hydrogen-to-carbon (H : C), and org. mass-to-org. carbon (OM : OC) ratios, and of carbon oxidn. state ‾(O‾ SC) for a vastly expanded lab. data set of multifunctional oxidized OA stds. For the expanded std. data set, the method introduced by Aiken et al. (2008), which uses exptl. measured ion intensities at all ions to det. elemental ratios (referred to here as "Aiken-Explicit"), reproduces known O : C and H : C ratio values within 20% (av. abs. value of relative errors) and 12%, resp. The more commonly used method, which uses empirically estd. H2O+ and CO+ ion intensities to avoid gas phase air interferences at these ions (referred to here as "Aiken-Ambient"), reproduces O : C and H : C of multifunctional oxidized species within 28 and 14% of known values. The values from the latter method are systematically biased low, however, with larger biases obsd. for alcs. and simple diacids. A detailed examn. of the H2O+, CO+, and CO2+ fragments in the high-resoln. mass spectra of the std. compds. indicates that the Aiken-Ambient method underestimates the CO+ and esp. H2O+ produced from many oxidized species. Combined AMS-vacuum UV (VUV) ionization measurements indicate that these ions are produced by dehydration and decarboxylation on the AMS vaporizer (usually operated at 600 °C). Thermal decompn. is obsd. to be efficient at vaporizer temps. down to 200 °C. These results are used together to develop an "Improved-Ambient" elemental anal. method for AMS spectra measured in air. The Improved-Ambient method uses specific ion fragments as markers to correct for mol. functionality-dependent systematic biases and reproduces known O : C (H : C) ratios of individual oxidized stds. within 28% (13%) of the known mol. values. The error in Improved-Ambient O : C (H : C) values is smaller for theor. std. mixts. of the oxidized org. stds., which are more representative of the complex mix of species present in ambient OA. For ambient OA, the Improved-Ambient method produces O : C (H : C) values that are 27% (11%) larger than previously published Aiken-Ambient values; a corresponding increase of 9% is obsd. for OM : OC values. These results imply that ambient OA has a higher relative oxygen content than previously estd. The‾ ‾OSC values calcd. for ambient OA by the two methods agree well, however (av. relative difference of 0.06‾ ‾OSC units). This indicates that‾ ‾OSC is a more robust metric of oxidn. than O : C, likely since‾ ‾OSC is not affected by hydration or dehydration, either in the atm. or during anal.
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    Aiken, A. C.; DeCarlo, P. F.; Jimenez, J. L. Elemental Analysis of Organic Species with Electron Ionization High-Resolution Mass Spectrometry. Anal. Chem. 2007, 79, 8350– 8358,  DOI: 10.1021/ac071150w
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    Elemental analysis of organic species with electron ionization high-resolution mass spectrometry
    Aiken, Allison C.; DeCarlo, Peter F.; Jimenez, Jose L.
    Analytical Chemistry (Washington, DC, United States) (2007), 79 (21), 8350-8358CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
    The authors present a new elemental anal. (EA) technique for org. species (CHNO) that allows fast online anal. (10 s) and reduces the required sample size to ∼1 ng, ∼6 orders of magnitude less than std. techniques. The compn. of the analyzed samples is approximated by the av. elemental compn. of the ions from high-resoln. electron ionization (EI) mass spectra. EA of org. species can be performed on org./inorg. mixts. Elemental ratios for the total org. mass, such as oxygen/carbon (O/C), hydrogen/carbon (H/C), and nitrogen/carbon (N/C), in addn. to the org. mass to org. carbon ratio (OM/OC), can be detd. As deviations between the mol. and the ionic compn. can appear due to chem. influences on the ion fragmentation processes, the method was evaluated and calibrated using spectra from 20 compds. from the NIST database and from 35 lab. stds. sampled with the high-resoln. time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The anal. of AMS (NIST) spectra indicates that quantification of O/C is possible with an error (av. abs. value of the relative error) of 30% (17%) for individual species. Precision is much better than accuracy at ±5% in the absence of air for AMS data. AMS OM/OC has an av. error of 5%. Addnl. calibration is recommended for types of species very different from those analyzed here. EA was applied to org. mixts. and ambient aerosols (sampled at 20 s from aircraft). The technique is also applicable to other EI-HRMS measurements such as direct injection MS.
  60. 60
    Stefenelli, G.; Pospisilova, V.; Lopez-Hilfiker, F. D.; Daellenbach, K. R.; Hüglin, C.; Tong, Y.; Baltensperger, U.; Prévôt, A. S. H.; Slowik, J. G. Organic Aerosol Source Apportionment in Zurich Using an Extractive Electrospray Ionization Time-of-Flight Mass Spectrometer (EESI-TOF-MS) -- Part 1: Biogenic Influences and Day-Night Chemistry in Summer. Atmos. Chem. Phys. 2019, 19, 14825– 14848,  DOI: 10.5194/acp-19-14825-2019
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    Organic aerosol source apportionment in Zurich using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) - part 1: biogenic influences and day-night chemistry in summer
    Stefenelli, Giulia; Pospisilova, Veronika; Lopez-Hilfiker, Felipe D.; Daellenbach, Kaspar R.; Huglin, Christoph; Tong, Yandong; Baltensperger, Urs; Prevot, Andre S. H.; Slowik, Jay G.
    Atmospheric Chemistry and Physics (2019), 19 (23), 14825-14848CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Improving the understanding of the health and climate impacts of aerosols remains challenging and is restricted by the limitations of current measurement techniques. Detailed investigation of secondary org. aerosol (SOA), which is typically the dominating fraction of the org. aerosol (OA), requires instrumentation capable of real-time, in situ measurements of mol. compn. In this study, we present the first ambient measurements by a novel extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS). The EESI-TOF-MS was deployed along with a high-resoln. time-of-flight aerosol mass spectrometer (HR-ToF-AMS) during summer 2016 at an urban location (Zurich, Switzerland). Pos. matrix factorization (PMF), implemented within the Multilinear Engine (ME-2), was applied to the data from both instruments to quantify the primary and secondary contributions to OA. From the EESI-TOF-MS anal., a six-factor soln. was selected as the most representative and interpretable soln. for the investigated dataset, including two primary and four secondary factors. The primary factors are dominated by cooking and cigarette smoke signatures while the secondary factors are discriminated according to their daytime (two factors) and night-time (two factors) chem. All four factors showed strong influence by biogenic emissions but exhibited significant day-night differences.
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    Tiitta, P.; Leskinen, A.; Hao, L.; Yli-Pirilä, P.; Kortelainen, M.; Grigonyte, J.; Tissari, J.; Lamberg, H.; Hartikainen, A.; Kuuspalo, K.; Kortelainen, A.-M.; Virtanen, A.; Lehtinen, K. E. J.; Komppula, M.; Pieber, S.; Prévôt, A. S. H.; Onasch, T. B.; Worsnop, D. R.; Czech, H.; Zimmermann, R.; Jokiniemi, J.; Sippula, O. Transformation of Logwood Combustion Emissions in a Smog Chamber: Formation of Secondary Organic Aerosol and Changes in the Primary Organic Aerosol upon Daytime and Nighttime Aging. Atmos. Chem. Phys. 2016, 16, 13251– 13269,  DOI: 10.5194/acp-16-13251-2016
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    Transformation of logwood combustion emissions in a smog chamber: formation of secondary organic aerosol and changes in the primary organic aerosol upon daytime and nighttime aging
    Tiitta, Petri; Leskinen, Ari; Hao, Liqing; Yli-Pirila, Pasi; Kortelainen, Miika; Grigonyte, Julija; Tissari, Jarkko; Lamberg, Heikki; Hartikainen, Anni; Kuuspalo, Kari; Kortelainen, Aki-Matti; Virtanen, Annele; Lehtinen, Kari E. J.; Komppula, Mika; Pieber, Simone; Prevot, Andre S. H.; Onasch, Timothy B.; Worsnop, Douglas R.; Czech, Hendryk; Zimmermann, Ralf; Jokiniemi, Jorma; Sippula, Olli
    Atmospheric Chemistry and Physics (2016), 16 (20), 13251-13269CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Org. aerosols (OA) derived from small-scale wood combustion emissions are not well represented by current emissions inventories and models, although they contribute substantially to the atm. particulate matter (PM) levels. In this work, a 29 m3 smog chamber in the ILMARI facility of the University of Eastern Finland was utilized to investigate the formation of secondary org. aerosol (SOA) from a small-scale modern masonry heater commonly used in northern Europe. Emissions were oxidatively aged in the smog chamber for a variety of dark (i.e., O3 and NO3) and UV (i.e., OH) conditions, with OH concn. levels of (0.5-5) × 106 mols. cm-3, achieving equiv. atm. aging of up to 18 h. An aerosol mass spectrometer characterized the direct OA emissions and the SOA formed from the combustion of three wood species (birch, beech and spruce) using two ignition processes (fast ignition with a VOC-to-NOx ratio of 3 and slow ignition with a ratio of 5). Dark and UV aging increased the SOA mass fraction with av. SOA productions 2.0 times the initial OA mass loadings. SOA enhancement was found to be higher for the slow ignition compared with fast ignition conditions. Pos. matrix factorization (PMF) was used to sep. SOA, primary org. aerosol (POA) and their subgroups from the total OA mass spectra. PMF anal. identified two POA and three SOA factors that correlated with the three major oxidizers: ozone, the nitrate radical and the OH radical. Organonitrates (ONs) were obsd. to be emitted directly from the wood combustion and addnl. formed during oxidn. via NO3 radicals (dark aging), suggesting small-scale wood combustion may be a significant ON source. POA was oxidized after the ozone addn., forming aged POA, and after 7 h of aging more than 75 % of the original POA was transformed. This process may involve evapn. and homogeneous gas-phase oxidn. as well as heterogeneous oxidn. of particulate org. matter. The results generally prove that logwood burning emissions are the subject of intensive chem. processing in the atm., and the timescale for these transformations is relatively short, i.e., hours.
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    Chhabra, P. S.; Flagan, R. C.; Seinfeld, J. H. Elemental Analysis of Chamber Organic Aerosol Using an Aerodyne High-Resolution Aerosol Mass Spectrometer. Atmos. Chem. Phys. 2010, 10, 4111– 4131,  DOI: 10.5194/acp-10-4111-2010
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    Elemental analysis of chamber organic aerosol using an aerodyne high-resolution aerosol mass spectrometer
    Chhabra, P. S.; Flagan, R. C.; Seinfeld, J. H.
    Atmospheric Chemistry and Physics (2010), 10 (9), 4111-4131CODEN: ACPTCE; ISSN:1680-7316. (Copernicus Publications)
    The elemental compn. of lab. chamber secondary org. aerosol (SOA) from glyoxal uptake, α-pinene ozonolysis, isoprene photooxidn., single-ring arom. photooxidn., and naphthalene photooxidn. is evaluated using Aerodyne high-resoln. time-of-flight mass spectrometer data. SOA O/C ratios range from 1.13 for glyoxal uptake expts. to 0.30-0.43 for α-pinene ozonolysis. The elemental compn. of α-pinene and naphthalene SOA is also confirmed by offline mass spectrometry. The fraction of org. signal at m/z 44 is generally a good measure of SOA oxygenation for α-pinene/O3, isoprene/high-NOx, and naphthalene SOA systems. The agreement between measured and estd. O/C ratios tends to get closer as the fraction of org. signal at m/z 44 increases. This is in contrast to the glyoxal uptake system, in which m/z 44 substantially underpredicts O/C. Although chamber SOA has generally been considered less oxygenated than ambient SOA, single-ring arom.- and naphthalene-derived SOA can reach O/C ratios upward of 0.7, well within the range of ambient PMF component OOA, though still not as high as some ambient measurements. The spectra of arom. and isoprene-high-NOx SOA resemble that of OOA, but the spectrum of glyoxal uptake does not resemble that of any ambient org. aerosol PMF component.
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    Garmash, O.; Rissanen, M. P.; Pullinen, I.; Schmitt, S.; Kausiala, O.; Tillmann, R.; Zhao, D.; Percival, C.; Bannan, T. J.; Priestley, M.; Hallquist, Å. M.; Kleist, E.; Kiendler-Scharr, A.; Hallquist, M.; Berndt, T.; McFiggans, G.; Wildt, J.; Mentel, T. F.; Ehn, M. Multi-Generation OH Oxidation as a Source for Highly Oxygenated Organic Molecules from Aromatics. Atmos. Chem. Phys. 2020, 20, 515– 537,  DOI: 10.5194/acp-20-515-2020
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    Atmospheric Chemistry and Physics (2020), 20 (1), 515-537CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Recent studies have recognized highly oxygenated org. mols. (HOMs) in the atm. as important in the formation of secondary org. aerosol (SOA). A large no. of studies have focused on HOM formation from oxidn. of biogenically emitted monoterpenes. However, HOM formation from anthropogenic vapors has so far received much less attention. Previous studies have identified the importance of arom. volatile org. compds. (VOCs) for SOA formation. In this study, we investigated several arom. compds., benzene (C6H6), toluene (C7H8), and naphthalene (C10H8), for their potential to form HOMs upon reaction with hydroxyl radicals (OH). We performed flow tube expts. with all three VOCs and focused in detail on benzene HOM formation in the Julich Plant Atm. Chamber (JPAC). In JPAC, we also investigated the response of HOMs to NOx and seed aerosol. Using a nitrate-based chem. ionisation mass spectrometer (CI-APi-TOF), we obsd. the formation of HOMs in the flow reactor oxidn. of benzene from the first OH attack. However, in the oxidn. of toluene and naphthalene, which were injected at lower concns., multigeneration OH oxidn. seemed to impact the HOM compn. We tested this in more detail for the benzene system in the JPAC, which allowed for studying longer residence times. The results showed that the apparent molar benzene HOM yield under our exptl. conditions varied from 4.1% to 14.0%, with a strong dependence on the OH concn., indicating that the majority of obsd. HOMs formed through multiple OH-oxidn. steps. The compn. of the identified HOMs in the mass spectrum also supported this hypothesis. By injecting only phenol into the chamber, we found that phenol oxidn. cannot be solely responsible for the obsd. HOMs in benzene expts. When NOx was added to the chamber, HOM compn. changed and many oxygenated nitrogen-contg. products were obsd. in CI-APi-TOF. Upon seed aerosol injection, the HOM loss rate was higher than predicted by irreversible condensation, suggesting that some undetected oxygenated intermediates also condensed onto seed aerosol, which is in line with the hypothesis that some of the HOMs were formed in multi-generation OH oxidn. Based on our results, we conclude that HOM yield and compn. in arom. systems strongly depend on OH and VOC concn. and more studies are needed to fully understand this effect on the formation of HOMs and, consequently, SOA. We also suggest that the dependence of HOM yield on chamber conditions may explain part of the variability in SOA yields reported in the literature and strongly advise monitoring HOMs in future SOA studies.
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    Kiendler-Scharr, A.; Mensah, A. A.; Friese, E.; Topping, D.; Nemitz, E.; Prevot, A. S. H.; Äijälä, M.; Allan, J.; Canonaco, F.; Canagaratna, M.; Carbone, S.; Crippa, M.; Dall Osto, M.; Day, D. A.; De Carlo, P.; Di Marco, C. F.; Elbern, H.; Eriksson, A.; Freney, E.; Hao, L.; Herrmann, H.; Hildebrandt, L.; Hillamo, R.; Jimenez, J. L.; Laaksonen, A.; McFiggans, G.; Mohr, C.; O’Dowd, C.; Otjes, R.; Ovadnevaite, J.; Pandis, S. N.; Poulain, L.; Schlag, P.; Sellegri, K.; Swietlicki, E.; Tiitta, P.; Vermeulen, A.; Wahner, A.; Worsnop, D.; Wu, H.-C. Ubiquity of Organic Nitrates from Nighttime Chemistry in the European Submicron Aerosol. Geophys. Res. Lett. 2016, 43, 7735– 7744,  DOI: 10.1002/2016GL069239
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    Ubiquity of organic nitrates from night time chemistry in the European submicron aerosol
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    In the atm. nighttime removal of volatile org. compds. is initiated to a large extent by reaction with the nitrate radical (NO3) forming org. nitrates which partition between gas and particulate phase. Here we show based on particle phase measurements performed at a suburban site in the Netherlands that org. nitrates contribute substantially to particulate nitrate and org. mass. Comparisons with a chem. transport model indicate that most of the measured particulate org. nitrates are formed by NO3 oxidn. Using aerosol compn. data from three intensive observation periods at numerous measurement sites across Europe, we conclude that org. nitrates are a considerable fraction of fine particulate matter (PM1) at the continental scale. Org. nitrates represent 34% to 44% of measured submicron aerosol nitrate and are found at all urban and rural sites, implying a substantial potential of PM redn. by NOx emission control.
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    Pye, H. O. T.; Luecken, D. J.; Xu, L.; Boyd, C. M.; Ng, N. L.; Baker, K. R.; Ayres, B. R.; Bash, J. O.; Baumann, K.; Carter, W. P. L.; Edgerton, E.; Fry, J. L.; Hutzell, W. T.; Schwede, D. B.; Shepson, P. B. Modeling the Current and Future Roles of Particulate Organic Nitrates in the Southeastern United States. Environ. Sci. Technol. 2015, 49, 14195– 14203,  DOI: 10.1021/acs.est.5b03738
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    Environmental Science & Technology (2015), 49 (24), 14195-14203CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Org. nitrates are an important aerosol constituent in locations where biogenic hydrocarbon emissions mix with anthropogenic NOx sources. While regional and global chem. transport models may include a representation of org. aerosol from monoterpene reactions with NO3- radicals (primary source of particle-phase org. NO3- in the southeastern US), secondary org. aerosol (SOA) models can underestimate yields. SOA parametrizations do not explicitly account for org. NO3- compds. produced in the gas phase. This work developed a coupled gas/aerosol system to describe formation and subsequent aerosol-phase partitioning of org. NO3- from isoprene and monoterpenes, focusing on the southeastern US. Org. aerosol and gas-phase org. NO3- concns. improved when particulate org. NO3- were assumed to undergo rapid (τ = 3 h) pseudo-hydrolysis resulting in HNO3 and non-volatile secondary org. aerosol formation. Also, up to 60% of less oxidized-oxygenated org. aerosol could be accounted for by org. NO3--mediated chem. during the Southern Oxidants and Aerosol Study (SOAS). A 25% redn. in NOx (NO + NO2) emissions was predicted to cause a 9% redn. in org. aerosols for June 2013 SOAS conditions at Centerville, Alabama.

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  • Abstract

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    Figure 1

    Figure 1. SOA mass evolution after the start of chemistry for (a) aromatics + NO3 and (b) aromatics + OH. Also included are the particle-phase nitrate and sulfate concentrations measured by the AMS. Note, the background of NO3– is ∼1 μg m–3 in our OH experiments, which may come from incorporation of HNO3 left over from the NO3 experiments. The zero on the x-axis represents the time of the start of the reaction, i.e., when VOCs are first exposed to radicals. Pink shading denotes the time periods used to determine representative mass spectra for the aromatics + NO3 (c) and aromatics + OH (d) systems. These mass spectra are represented as carbon number distributions, with bins divided into CHO (left bar, blue-purple-green shading) and CHON (right bar, yellow-red-brown shading), and stacked vertically by number of oxygen atoms.

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    Figure 2

    Figure 2. Time-series O/C, H/C, and N/C ratios obtained from the AMS for (a) NO3 experiment and (b) OH experiment.

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    Figure 3

    Figure 3. (a) Temporal evolution of fractional contributions from species in the aromatics + NO3 experiment color-coded by their carbon number (b) Same plot for the aromatics + OH experiment. (c) Mass-defect plot (exact mass minus nearest integer mass vs m/z) color-coded by ratio of intensity at 210 min to intensity at 30 min for the aromatics + NO3 system. Closed circles depict CHO C6–C9 monomers, whereas open circles depict CHO C13–C18 compounds. The closed and open diamonds depict CHON monomer and dimer species, respectively. (d) Mass-defect plot color-coded by ratio of intensity at 210 min to intensity at 30 min for the aromatics + OH system.

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    Figure 4

    Figure 4. Box–whisker plots of decay rates calculated for CxHyOz type C9–C10 monomers and C20 dimer species in α-pinene + O3 SOA (28) highlighted by green areas. The points inside the respective box depict the mean rate of decay, whereas the diamonds adjacent to the boxed depict the spread of data. Similarly, the decay rates highlighted by pink areas are from CxHyOzN type C7–C8 monomers and C14–C17 dimers observed in the aromatics + NO3 system in this study.

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  • References

    This article references 65 other publications.

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      3
      Wood burning: A major source of Volatile Organic Compounds during wintertime in the Paris region
      Languille, Baptiste; Gros, Valerie; Petit, Jean-Eudes; Honore, Cecile; Baudic, Alexia; Perrussel, Olivier; Foret, Gilles; Michoud, Vincent; Truong, Francois; Bonnaire, Nicolas; Sarda-Esteve, Roland; Delmotte, Marc; Feron, Anais; Maisonneuve, Franck; Gaimoz, Cecile; Formenti, Paola; Kotthaus, Simone; Haeffelin, Martial; Favez, Olivier
      Science of the Total Environment (2020), 711 (), 135055CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
      Wood burning, widely used for domestic heating, was identified as a ubiquitous pollution source in urban areas, particularly during cold months. This work, based on a 3.5 half winter months field campaign in Paris, France, measured volatile org. compds. (VOC) by proton transfer reaction mass spectrometry, and black C (BC) concns. Several VOC were identified as strongly wood burning-influenced (e.g., acetic acid, furfural), or traffic-influenced (e.g., toluene, C8 aroms.). Methylbutenone, benzenediol, and butandione were identified for the first time in ambient air as wood burning-related. A pos. matrix factorization anal. highlighted wood burning as the most important VOC source during the winter season. (47%). Traffic accounted for ∼22% of VOC measured in the same period; solvent use plus background together accounted for the remaining fraction. A comparison with a regional emission inventory showed good consistency for benzene and xylenes but inventory revisions should be considered for several VOC, e.g., acetic acid, C9 aroms., and methanol. Complementary measurements simultaneously acquired at other sites in Ile-de-France (Paris region) enabled spatial variabilities to be evaluated. Traffic emissions effect on studied pollutants showed a clear neg. gradient from roadside to suburban sites; wood burning pollution was fairly homogeneous over the region.
    4. 4
      Borbon, A.; Gilman, J. B.; Kuster, W. C.; Grand, N.; Chevaillier, S.; Colomb, A.; Dolgorouky, C.; Gros, V.; Lopez, M.; Sarda-Esteve, R.; Holloway, J.; Stutz, J.; Petetin, H.; McKeen, S.; Beekmann, M.; Warneke, C.; Parrish, D. D.; de Gouw, J. A. Emission Ratios of Anthropogenic Volatile Organic Compounds in Northern Mid-Latitude Megacities: Observations versus Emission Inventories in Los Angeles and Paris. J. Geophys. Res.: Atmos. 2013, 118, 2041– 2057,  DOI: 10.1002/jgrd.50059
      4
      Emission ratios of anthropogenic volatile organic compounds in northern mid-latitude megacities: observations versus emission inventories in Los Angeles and Paris
      Borbon, Agnes; Gilman, J. B.; Kuster, W. C.; Grand, N.; Chevaillier, S.; Colomb, A.; Dolgorouky, C.; Gros, V.; Lopez, M.; Sarda-Esteve, R.; Holloway, J.; Stutz, J.; Petetin, H.; McKeen, S.; Beekmann, M.; Warneke, C.; Parrish, D. D.; de Gouw, J. A.
      Journal of Geophysical Research: Atmospheres (2013), 118 (4), 2041-2057CODEN: JGRDE3; ISSN:2169-8996. (Wiley-Blackwell)
      Ground-based and airborne volatile org. compd. (VOC) measurements in Los Angeles, California, and Paris, France, during the Research at the Nexus of Air Quality and Climate Change (CalNex) and Megacities: Emissions, Urban, Regional and Global Atm. Pollution and Climate Effects, and Integrated Tools for Assessment and Mitigation (MEGAPOLI) campaigns, resp., are used to examine the spatial variability of the compn. of anthropogenic VOC urban emissions and to evaluate regional emission inventories. Two independent methods that take into account the effect of chem. were used to det. the emission ratios of anthropogenic VOCs (including anthropogenic isoprene and oxygenated VOCs) over carbon monoxide (CO) and acetylene. Emission ratios from both methods agree within ±20%, showing the reliability of our approach. Emission ratios for alkenes, alkanes, and benzene are fairly similar between Los Angeles and Paris, whereas the emission ratios for C7-C9 aroms. in Paris are higher than in Los Angeles and other French and European Union urban areas by a factor of 2-3. The results suggest that the emissions of gasoline-powered vehicles still dominate the hydrocarbon distribution in northern mid-latitude urban areas, which disagrees with emission inventories. However, regional characteristics like the gasoline compn. could affect the compn. of hydrocarbon emissions. The obsd. emission ratios show large discrepancies by a factor of 2-4 (alkanes and oxygenated VOC) with the ones derived from four ref. emission databases. A bias in CO emissions was also evident for both megacities. Nevertheless, the difference between measurements and inventory in terms of the overall OH reactivity is, in general, lower than 40%, and the potential to form secondary org. aerosols (SOA) agrees within 30% when considering volatile org. emissions as the main SOA precursors.
    5. 5
      Mehra, A.; Wang, Y.; Krechmer, J. E.; Lambe, A.; Majluf, F.; Morris, M. A.; Priestley, M.; Bannan, T. J.; Bryant, D. J.; Pereira, K. L.; Hamilton, J. F.; Rickard, A. R.; Newland, M. J.; Stark, H.; Croteau, P.; Jayne, J. T.; Worsnop, D. R.; Canagaratna, M. R.; Wang, L.; Coe, H. Evaluation of the Chemical Composition of Gas- and Particle-Phase Products of Aromatic Oxidation. Atmos. Chem. Phys. 2020, 20, 9783– 9803,  DOI: 10.5194/acp-20-9783-2020
      5
      Evaluation of the chemical composition of gas- and particle-phase products of aromatic oxidation
      Mehra, Archit; Wang, Yuwei; Krechmer, Jordan E.; Lambe, Andrew; Majluf, Francesca; Morris, Melissa A.; Priestley, Michael; Bannan, Thomas J.; Bryant, Daniel J.; Pereira, Kelly L.; Hamilton, Jacqueline F.; Rickard, Andrew R.; Newland, Mike J.; Stark, Harald; Croteau, Philip; Jayne, John T.; Worsnop, Douglas R.; Canagaratna, Manjula R.; Wang, Lin; Coe, Hugh
      Atmospheric Chemistry and Physics (2020), 20 (16), 9783-9803CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Arom. volatile org. compds. (VOCs) are key anthropogenic pollutants emitted to the atm. and are important for both ozone and secondary org. aerosol (SOA) formation in urban areas. Recent studies have indicated that arom. hydrocarbons may follow previously unknown oxidn. chem. pathways, including autoxidn. that can lead to the formation of highly oxidised products. In this study we evaluate the gas- and particle-phase ions measured by online mass spectrometry during the hydroxyl radical oxidn. of substituted C9-arom. isomers (1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, propylbenzene and isopropylbenzene) and a substituted polyarom. hydrocarbon (1-methylnaphthalene) under low- and medium-NOx conditions. A time-of-flight chem. ionisation mass spectrometer (ToF-CIMS) with iodide-anion ionisation was used with a filter inlet for gases and aerosols (FIGAERO) for the detection of products in the particle phase, while a Vocus protontransfer-reaction mass spectrometer (Vocus-PTR-MS) was used for the detection of products in the gas phase. The signal of product ions obsd. in the mass spectra were compared for the different precursors and exptl. conditions. The majority of mass spectral product signal in both the gas and particle phases comes from ions which are common to all precursors, though signal distributions are distinct for different VOCs. Gas- and particle-phase compn. are distinct from one another. Ions corresponding to products contained in the near-explicit gas phase Master Chem. Mechanism (MCM version 3.3.1) are utilized as a benchmark of current scientific understanding, and a comparison of these with observations shows that the MCM is missing a range of highly oxidised products from its mechanism. In the particle phase, the bulk of the product signal from all precursors comes from ring scission ions, a large proportion of which are more oxidised than previously reported and have undergone further oxidn. to form highly oxygenated org. mols. (HOMs). Under the perturbation of OH oxidn. with increased NOx, the contribution of HOM-ion signals to the particle-phase signal remains elevated for more substituted arom. precursors. Up to 43 % of product signal comes from ring-retaining ions including HOMs; this is most important for the more substituted aroms. Unique products are a minor component in these systems, and many of the dominant ions have ion formulas concurrent with other systems, highlighting the challenges in utilizing marker ions for SOA.
    6. 6
      Seinfeld, J. H.; Pandis, S. N. Atmospheric Chemistry and Physics: From Air Pollution to Climate Change; John Wiley & Sons, Ltd, 2016.
      There is no corresponding record for this reference.
    7. 7
      Finlayson-Pitts, B. J.; Pitts, J. N. CHAPTER 9─Particles in the Troposphere. In Chemistry of the Upper and Lower Atmosphere; Finlayson-Pitts, B. J., Pitts, J. N., Eds.; Academic Press: San Diego, 2000; pp 349– 435.
      There is no corresponding record for this reference.
    8. 8
      Guo, S.; Hu, M.; Zamora, M. L.; Peng, J.; Shang, D.; Zheng, J.; Du, Z.; Wu, Z.; Shao, M.; Zeng, L.; Molina, M. J.; Zhang, R. Elucidating Severe Urban Haze Formation in China. Proc. Natl. Acad. Sci. U.S.A. 2014, 111, 17373– 17378,  DOI: 10.1073/pnas.1419604111
      8
      Elucidating severe urban haze formation in China
      Guo, Song; Hu, Min; Zamora, Misti L.; Peng, Jianfei; Shang, Dongjie; Zheng, Jing; Du, Zhuofei; Wu, Zhijun; Shao, Min; Zeng, Limin; Molina, Mario J.; Zhang, Renyi
      Proceedings of the National Academy of Sciences of the United States of America (2014), 111 (49), 17373-17378CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
      As the world's 2nd largest economy, China has experienced severe haze pollution, with fine particulate matter (PM) recently reaching unprecedentedly high levels across many cities, and an understanding of the PM formation mechanism is crit. in the development of efficient mediation policies to minimize its regional to global impacts. We demonstrate a periodic cycle of PM episodes in Beijing that is governed by meteorol. conditions and characterized by 2 distinct aerosol formation processes of nucleation and growth, but with a small contribution from primary emissions and regional transport of particles. Nucleation consistently precedes a polluted period, producing a high no. concn. of nano-sized particles under clean conditions. Accumulation of the particle mass concn. exceeding several hundred micrograms per cubic meter is accompanied by a continuous size growth from the nucleation-mode particles over multiple days to yield numerous larger particles, distinctive from the aerosol formation typically obsd. in other regions worldwide. The particle compns. in Beijing, on the other hand, exhibit a similarity to those commonly measured in many global areas, consistent with the chem. constituents dominated by secondary aerosol formation. Our results highlight that regulatory controls of gaseous emissions for volatile org. compds. and NOx from local transportation and SO2 from regional industrial sources represent the key steps to reduce the urban PM level in China.
    9. 9
      Ng, N. L.; Kroll, J. H.; Chan, A. W. H.; Chhabra, P. S.; Flagan, R. C.; Seinfeld, J. H. Secondary organic aerosol formation from m-xylene, toluene, and benzene. Atmos. Chem. Phys. 2007, 7, 3909– 3922,  DOI: 10.5194/acp-7-3909-2007
      9
      Secondary organic aerosol formation from m-xylene, toluene, and benzene
      Ng, N. L.; Kroll, J. H.; Chan, A. W. H.; Chhabra, P. S.; Flagan, R. C.; Seinfeld, J. H.
      Atmospheric Chemistry and Physics (2007), 7 (14), 3909-3922CODEN: ACPTCE; ISSN:1680-7316. (European Geosciences Union)
      Secondary org. aerosol (SOA) formation from the photooxidn. of m-xylene, toluene, and benzene is investigated in the Caltech environmental chambers. Expts. are performed under two limiting NOx conditions; under high-NOx conditions the peroxy radicals (RO2) react only with NO, while under low-NOx conditions they react only with HO2. For all three aroms. studied (m-xylene, toluene, and benzene), the SOA yields (defined as the ratio of the mass of org. aerosol formed to the mass of parent hydrocarbon reacted) under low-NOx conditions substantially exceed those under high-NOx conditions, suggesting the importance of peroxy radical chem. in SOA formation. Under low-NOx conditions, the SOA yields for m-xylene, toluene, and benzene are const. (36%, 30%, and 37%, resp.), indicating that the SOA formed is effectively nonvolatile under the range of Mo(>10 μg m-3) studied. Under high-NOx conditions, aerosol growth occurs essentially immediately, even when NO concn. is high. The SOA yield curves exhibit behavior similar to that obsd. by Odum et al. (1996, 1997a, b), although the values are somewhat higher than in the earlier study. The yields measured under high-NOx conditions are higher than previous measurements, suggesting a "rate effect" in SOA formation, in which SOA yields are higher when the oxidn. rate is faster. Expts. carried out in the presence of acidic seed aerosol reveal no change of SOA yields from the aroms. as compared with those using neutral seed aerosol.
    10. 10
      Zhang, R.; Wang, G.; Guo, S.; Zamora, M. L.; Ying, Q.; Lin, Y.; Wang, W.; Hu, M.; Wang, Y. Formation of Urban Fine Particulate Matter. Chem. Rev. 2015, 115, 3803– 3855,  DOI: 10.1021/acs.chemrev.5b00067
      10
      Formation of Urban Fine Particulate Matter
      Zhang, Renyi; Wang, Gehui; Guo, Song; Zamora, Misti L.; Ying, Qi; Lin, Yun; Wang, Weigang; Hu, Min; Wang, Yuan
      Chemical Reviews (Washington, DC, United States) (2015), 115 (10), 3803-3855CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review concerning the fundamental chem. aspects relevant to urban fine particulate matter (PM) formation, particularly processes governing particle no., size, and chem. compn., are given. Topics discussed include: introduction; historical perspectives (London fog, Los Angeles smog, Beijing haze); urban fine PM origins (primary emissions, new particle formation); growth processes (org. matter gas/particle partitioning, org. matter particle phase reactions [hydration and acid-catalyzed reactions, basic species reactions], SO42- and NO3- formation, primary particle aging); atm. measurements (anal. techniques [gaseous aerosol precursors, PM], anal. approaches, spatiotemporal characteristics of no. concn., size, chem. compn.m,, and other urban fine PM properties); atm. modeling (primary PM and gas precursor emissions, gaseous and multi-phase chem. [gaseous photochem. oxidn. mechanism, new particle formation, multi-phase processes], regional transport and removal processes); and future directions and conclusions.
    11. 11
      Lund, A. K.; Doyle-Eisele, M.; Lin, Y.-H.; Arashiro, M.; Surratt, J. D.; Holmes, T.; Schilling, K. A.; Seinfeld, J. H.; Rohr, A. C.; Knipping, E. M.; McDonald, J. D. The effects of α-pinene versus toluene-derived secondary organic aerosol exposure on the expression of markers associated with vascular disease. Inhalation Toxicol. 2013, 25, 309– 324,  DOI: 10.3109/08958378.2013.782080
      11
      The effects of α-pinene versus toluene-derived secondary organic aerosol exposure on the expression of markers associated with vascular disease
      Lund, Amie K.; Doyle-Eisele, Melanie; Lin, Ying-Hsuan; Arashiro, Maiko; Surratt, Jason D.; Holmes, Tom; Schilling, Katherine A.; Seinfeld, John H.; Rohr, Annette C.; Knipping, Eladio M.; McDonald, Jacob D.
      Inhalation Toxicology (2013), 25 (6), 309-324CODEN: INHTE5; ISSN:0895-8378. (Informa Healthcare)
      To investigate the toxicol. effects of biogenic- vs. anthropogenic-source secondary org. aerosol (SOA) on the cardiovascular system, the Secondary Particulate Health Effects Research program irradn. chamber was used to expose atherosclerotic apolipoprotein E null (Apo E-/-) mice to SOA from the oxidn. of either α-pinene or toluene for 7 days. SOA atmospheres were produced to yield 250-300 μg/m3 of particulate matter and ratios of 10:1:1 α-pinene:nitrogen oxide (NOx):ammonia (NH3); 10:1:1:1 α-pinene:NOx:NH3:sulfur dioxide (SO2) or 10:1:1 toluene:NOx:NH3; and 10:1:1:1 toluene:NOx:NH3:SO2. Resulting effects on the cardiovascular system were assessed by measurement of vascular lipid peroxidn. (thiobarbituric acid reactive substance (TBARS)), as well as quantification of heme-oxygenase (HO)-1, endothelin (ET)-1, and matrix metalloproteinase (MMP)-9 mRNA expression for comparison to previous program exposure results. Consistent with similar previous studies, vascular TBARS were not increased significantly with any acute SOA exposure. However, vascular HO-1, MMP-9, and ET-1 obsd. in Apo E-/- mice exposed to α-pinene + NOx + NH3 + SO2 increased statistically, while α-pinene + NOx + NH3 exposure to either toluene + NOx + NH3 or toluene +NOx + NH3 + SO2 resulted in a decreased expression of these vascular factors. Such findings suggest that the specific chem. created by the presence or absence of acidic components may be important in SOA-mediated toxicity in the cardiovascular system and/or progression of cardiovascular disease.
    12. 12
      McDonald, J. D.; Doyle-Eisele, M.; Kracko, D.; Lund, A.; Surratt, J. D.; Hersey, S. P.; Seinfeld, J. H.; Rohr, A. C.; Knipping, E. M. Cardiopulmonary Response to Inhalation of Secondary Organic Aerosol Derived from Gas-Phase Oxidation of Toluene. Inhalation Toxicol. 2012, 24, 689– 697,  DOI: 10.3109/08958378.2012.712164
      12
      Cardiopulmonary response to inhalation of secondary organic aerosol derived from gas-phase oxidation of toluene
      McDonald, Jacob D.; Doyle-Eisele, Melanie; Kracko, Dean; Lund, Amie; Surratt, Jason D.; Hersey, Scott P.; Seinfeld, John H.; Rohr, Annette C.; Knipping, Eladio M.
      Inhalation Toxicology (2012), 24 (11), 689-697CODEN: INHTE5; ISSN:0895-8378. (Informa Healthcare)
      The biol. response to inhalation of secondary org. aerosol (SOA) was detd. in rodents exposed to SOA derived from the oxidn. of toluene, a precursor emitted from anthropogenic sources. SOA atmospheres were produced to yield 300 μg·m-3 of particulate matter (PM) plus accompanying gases. Whole-body exposures were conducted in mice to assess both pulmonary and cardiovascular effects. ApoE-/- mice were exposed for 7 days and measurements of TBARS and gene expression of heme-oxygenase-1 (HO-1), endothelin-1 (ET-1), and matrix metalloproteinase-9 (MMP-9) were made in aorta. Pulmonary inflammatory responses in both species were measured by bronchoalveolar lavage fluid (BALF) cell counts. No pulmonary inflammation was obsd. A mild response was obsd. in mouse aorta for the upregulation of ET-1 and HO-1, with a trend for increased MMP-9 and TBARS, and. Overall, toluene-derived SOA revealed limited biol. response compared with previous studies using this exposure protocol with other environmental pollutants.
    13. 13
      Tuet, W. Y.; Chen, Y.; Fok, S.; Champion, J. A.; Ng, N. L. Inflammatory Responses to Secondary Organic Aerosols (SOA) Generated from Biogenic and Anthropogenic Precursors. Atmos. Chem. Phys. 2017, 17, 11423– 11440,  DOI: 10.5194/acp-17-11423-2017
      13
      Inflammatory responses to secondary organic aerosols (SOA) generated from biogenic and anthropogenic precursors
      Tuet, Wing Y.; Chen, Yunle; Fok, Shierly; Champion, Julie A.; Ng, Nga L.
      Atmospheric Chemistry and Physics (2017), 17 (18), 11423-11440CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Cardiopulmonary health implications resulting from exposure to secondary org. aerosols (SOA), which comprise a significant fraction of ambient particulate matter (PM), have received increasing interest in recent years. In this study, alveolar macrophages were exposed to SOA generated from the photooxidn. of biogenic and anthropogenic precursors (isoprene, α-pinene, β-caryophyllene, pentadecane, m-xylene, and naphthalene) under different formation conditions (RO2 + HO2 vs. RO2 + NO dominant, dry vs. humid). Various cellular responses were measured, including reactive oxygen and nitrogen species (ROS/RNS) prodn. and secreted levels of cytokines, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). SOA precursor identity and formation condition affected all measured responses in a hydrocarbon-specific manner. With the exception of naphthalene SOA, cellular responses followed a trend where TNF-α levels reached a plateau with increasing IL-6 levels. ROS/RNS levels were consistent with relative levels of TNF-α and IL-6, due to their resp. inflammatory and anti-inflammatory effects. Exposure to naphthalene SOA, whose arom.-ring-contg. products may trigger different cellular pathways, induced higher levels of TNF-α and ROS/RNS than suggested by the trend. Distinct cellular response patterns were identified for hydrocarbons whose photooxidn. products shared similar chem. functionalities and structures, which suggests that the chem. structure (carbon chain length and functionalities) of photooxidn. products may be important for detg. cellular effects. A pos. nonlinear correlation was also detected between ROS/RNS levels and previously measured DTT (dithiothreitol) activities for SOA samples. In the context of ambient samples collected during summer and winter in the greater Atlanta area, all lab.-generated SOA produced similar or higher levels of ROS/RNS and DTT activities. These results suggest that the health effects of SOA are important considerations for understanding the health implications of ambient aerosols.
    14. 14
      Shiraiwa, M.; Ueda, K.; Pozzer, A.; Lammel, G.; Kampf, C. J.; Fushimi, A.; Enami, S.; Arangio, A. M.; Fröhlich-Nowoisky, J.; Fujitani, Y.; Furuyama, A.; Lakey, P. S. J.; Lelieveld, J.; Lucas, K.; Morino, Y.; Pöschl, U.; Takahama, S.; Takami, A.; Tong, H.; Weber, B.; Yoshino, A.; Sato, K. Aerosol Health Effects from Molecular to Global Scales. Environ. Sci. Technol. 2017, 51, 13545– 13567,  DOI: 10.1021/acs.est.7b04417
      14
      Aerosol Health Effects from Molecular to Global Scales
      Shiraiwa, Manabu; Ueda, Kayo; Pozzer, Andrea; Lammel, Gerhard; Kampf, Christopher J.; Fushimi, Akihiro; Enami, Shinichi; Arangio, Andrea M.; Frohlich-Nowoisky, Janine; Fujitani, Yuji; Furuyama, Akiko; Lakey, Pascale S. J.; Lelieveld, Jos; Lucas, Kurt; Morino, Yu; Poschl, Ulrich; Takahama, Satoshi; Takami, Akinori; Tong, Haijie; Weber, Bettina; Yoshino, Ayako; Sato, Kei
      Environmental Science & Technology (2017), 51 (23), 13545-13567CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      A review. Poor air quality is globally the largest environmental health risk. Epidemiol. studies have uncovered clear relationships of gaseous pollutants and particulate matter (PM) with adverse health outcomes, including mortality by cardiovascular and respiratory diseases. Studies of health impacts by aerosols are highly multidisciplinary with a broad range of scales in space and time. We assess recent advances and future challenges regarding aerosol effects on health from mol. to global scales through epidemiol. studies, field measurements, health-related properties of PM, and multiphase interactions of oxidants and PM upon respiratory deposition. Global modeling combined with epidemiol. exposure-response functions indicates that ambient air pollution causes more than four million premature deaths per yr. Epidemiol. studies usually refer to PM mass concns., but some health effects may relate to specific constituents such as bioaerosols, polycyclic arom. compds., and transition metals. Various anal. techniques and cellular and mol. assays are applied to assess the redox activity of PM and the formation of reactive oxygen species. Multiphase chem. interactions of lung antioxidants with atm. pollutants are crucial to the mechanistic and mol. understanding of oxidative stress upon respiratory deposition. The role of distinct PM components in health impacts and mortality needs to be clarified by integrated research on various spatiotemporal scales for better evaluation and mitigation of aerosol effects on public health in the Anthropocene.
    15. 15
      Liu, Q.; Baumgartner, J.; Zhang, Y.; Liu, Y.; Sun, Y.; Zhang, M. Oxidative Potential and Inflammatory Impacts of Source Apportioned Ambient Air Pollution in Beijing. Environ. Sci. Technol. 2014, 48, 12920– 12929,  DOI: 10.1021/es5029876
      15
      Oxidative Potential and Inflammatory Impacts of Source Apportioned Ambient Air Pollution in Beijing
      Liu, Qingyang; Baumgartner, Jill; Zhang, Yuanxun; Liu, Yanju; Sun, Yongjun; Zhang, Meigen
      Environmental Science & Technology (2014), 48 (21), 12920-12929CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Air pollution exposure is assocd. with a range of adverse health impacts. Knowing the air pollution chem. components and sources most responsible for these health effects could lead to an improved understanding of effect mechanisms and more targeted risk redn. strategies. This work measured daily ambient fine particulate matter (PM2.5) for 2 mo in peri-urban and central Beijing, China, and assessed the contribution of its chem. components to the oxidative potential of ambient air pollution using the dithiothreitol assay. Compn. data were using in a multivariate source apportionment model to det. PM contributions of 6 factors/sources/: Zn, Al, and Pb point factors; and secondary source (e.g., SO42-, NO32-), Fe, and soil dust sources. The relationship between reactive oxygen species (ROS) activity-related PM sources and inflammatory responses in human bronchial epithelial cells was examd. In peri-urban Beijing, soil dust accounted for the largest fraction (47%) of measured ROS variability. In central Beijing, a secondary source explained the greatest fraction (29%) of measured ROS variability. ROS activity of PM collected in central Beijing was exponentially assocd. with in-vivo inflammatory responses in epithelial cells (R2 = 0.65-0.89). A high correlation was obsd. among 3 ROS-related PM sources (Pb point and Zn factors, secondary source) and inflammatory marker expression (r = 0.45-0.80). Results suggested large differences in the contribution of different PM sources to ROS variability in central vs. peri-urban sites in Beijing; secondary sources may play an important role in PM2.5-related oxidative potential and inflammatory health impacts.
    16. 16
      Bates, J. T.; Weber, R. J.; Abrams, J.; Verma, V.; Fang, T.; Klein, M.; Strickland, M. J.; Sarnat, S. E.; Chang, H. H.; Mulholland, J. A.; Tolbert, P. E.; Russell, A. G. Reactive Oxygen Species Generation Linked to Sources of Atmospheric Particulate Matter and Cardiorespiratory Effects. Environ. Sci. Technol. 2015, 49, 13605– 13612,  DOI: 10.1021/acs.est.5b02967
      16
      Reactive Oxygen Species Generation Linked to Sources of Atmospheric Particulate Matter and Cardiorespiratory Effects
      Bates, Josephine T.; Weber, Rodney J.; Abrams, Joseph; Verma, Vishal; Fang, Ting; Klein, Mitchel; Strickland, Matthew J.; Sarnat, Stefanie Ebelt; Chang, Howard H.; Mulholland, James A.; Tolbert, Paige E.; Russell, Armistead G.
      Environmental Science & Technology (2015), 49 (22), 13605-13612CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Exposure to atm. fine particulate matter (PM2.5) is assocd. with cardiorespiratory morbidity and mortality, but the mechanisms are not well understood. We assess the hypothesis that PM2.5 induces oxidative stress in the body via catalytic generation of reactive oxygen species (ROS). A dithiothreitol (DTT) assay was used to measure the ROS-generation potential of water-sol. PM2.5. Source apportionment on ambient (Atlanta, GA) PM2.5 was performed using the chem. mass balance method with ensemble-averaged source impact profiles. Linear regression anal. was used to relate PM2.5 emission sources to ROS-generation potential and to est. historical levels of DTT activity for use in an epidemiol. anal. for the period of 1998-2009. Light-duty gasoline vehicles (LDGV) exhibited the highest intrinsic DTT activity, followed by biomass burning (BURN) and heavy-duty diesel vehicles (HDDV) (0.11 ± 0.02, 0.069 ± 0.02, and 0.052 ± 0.01 nmol/min μgsource, resp.). BURN contributed the largest fraction to total DTT activity over the study period, followed by LDGV and HDDV (45, 20, and 14%, resp.). DTT activity was more strongly assocd. with emergency department visits for asthma/wheezing and congestive heart failure than PM2.5. This work provides further epidemiol. evidence of a biol. plausible mechanism, that of oxidative stress, for assocns. of adverse health outcomes with PM2.5 mass and supports continued assessment of the utility of the DTT activity assay as a measure of ROS-generating potential of particles.
    17. 17
      Daellenbach, K. R.; Uzu, G.; Jiang, J.; Cassagnes, L.-E.; Leni, Z.; Vlachou, A.; Stefenelli, G.; Canonaco, F.; Weber, S.; Segers, A.; Kuenen, J. J. P.; Schaap, M.; Favez, O.; Albinet, A.; Aksoyoglu, S.; Dommen, J.; Baltensperger, U.; Geiser, M.; El Haddad, I.; Jaffrezo, J.-L.; Prévôt, A. S. H. Sources of Particulate-Matter Air Pollution and Its Oxidative Potential in Europe. Nature 2020, 587, 414– 419,  DOI: 10.1038/s41586-020-2902-8
      17
      Sources of particulate-matter air pollution and its oxidative potential in Europe
      Daellenbach, Kaspar R.; Uzu, Gaelle; Jiang, Jianhui; Cassagnes, Laure-Estelle; Leni, Zaira; Vlachou, Athanasia; Stefenelli, Giulia; Canonaco, Francesco; Weber, Samuel; Segers, Arjo; Kuenen, Jeroen J. P.; Schaap, Martijn; Favez, Olivier; Albinet, Alexandre; Aksoyoglu, Sebnem; Dommen, Josef; Baltensperger, Urs; Geiser, Marianne; El Haddad, Imad; Jaffrezo, Jean-Luc; Prevot, Andre S. H.
      Nature (London, United Kingdom) (2020), 587 (7834), 414-419CODEN: NATUAS; ISSN:0028-0836. (Nature Research)
      Abstr.: Particulate matter is a component of ambient air pollution that has been linked to millions of annual premature deaths globally1-3. Assessments of the chronic and acute effects of particulate matter on human health tend to be based on mass concn., with particle size and compn. also thought to play a part4. Oxidative potential has been suggested to be one of the many possible drivers of the acute health effects of particulate matter, but the link remains uncertain5-8. Studies investigating the particulate-matter components that manifest an oxidative activity have yielded conflicting results7. In consequence, there is still much to be learned about the sources of particulate matter that may control the oxidative potential concn.7. Here we use field observations and air-quality modeling to quantify the major primary and secondary sources of particulate matter and of oxidative potential in Europe. We find that secondary inorg. components, crustal material and secondary biogenic org. aerosols control the mass concn. of particulate matter. By contrast, oxidative potential concn. is assocd. mostly with anthropogenic sources, in particular with fine-mode secondary org. aerosols largely from residential biomass burning and coarse-mode metals from vehicular non-exhaust emissions. Our results suggest that mitigation strategies aimed at reducing the mass concns. of particulate matter alone may not reduce the oxidative potential concn. If the oxidative potential can be linked to major health impacts, it may be more effective to control specific sources of particulate matter rather than overall particulate mass.
    18. 18
      Puthussery, J. V.; Singh, A.; Rai, P.; Bhattu, D.; Kumar, V.; Vats, P.; Furger, M.; Rastogi, N.; Slowik, J. G.; Ganguly, D.; Prevot, A. S. H.; Tripathi, S. N.; Verma, V. Real-Time Measurements of PM2.5 Oxidative Potential Using a Dithiothreitol Assay in Delhi, India. Environ. Sci. Technol. Lett. 2020, 7, 504– 510,  DOI: 10.1021/acs.estlett.0c00342
      18
      Real-Time Measurements of PM2.5 Oxidative Potential Using a Dithiothreitol Assay in Delhi, India
      Puthussery, Joseph V.; Singh, Atinderpal; Rai, Pragati; Bhattu, Deepika; Kumar, Varun; Vats, Pawan; Furger, Markus; Rastogi, Neeraj; Slowik, Jay G.; Ganguly, Dilip; Prevot, Andre S. H.; Tripathi, Sachchida Nand; Verma, Vishal
      Environmental Science & Technology Letters (2020), 7 (7), 504-510CODEN: ESTLCU; ISSN:2328-8930. (American Chemical Society)
      The oxidative potential (OP) of ambient particulate matter (PM) is a metric commonly used to link the aerosol exposure to its adverse health effects. In this study, we report the first-ever real-time measurements of ambient PM2.5 OP based on a dithiothreitol (DTT) assay in Delhi, during a late winter season (Feb. 2019). The chem. compn. of PM was also measured using various collocated online instruments to identify the chem. components driving the PM2.5 OP. The hourly averaged OP during the entire campaign ranged from 0.49 to 3.60 nmol min-1 m-3, with an av. value of 1.57 ± 0.7 nmol min-1 m-3. The secondary org. aerosols appear to be the major driver for the variation in the intrinsic OP of PM2.5. Although the av. PM1 mass concn. at Delhi was 13 times the av. PM2.5 mass concn. reported in Illinois, USA, in a similar study, it was not accompanied by a proportionate increase in the OP (the av. vol.-normalized DTT activity of PM2.5 was only 5 times that reported in Illinois). These findings reveal substantial spatial heterogeneity in the redox properties of PM and highlight the importance of detg. the PM chem. compn. along with its mass concns. for predicting the overall health impacts assocd. with aerosol exposure.
    19. 19
      Kumar, V.; Giannoukos, S.; Haslett, S. L.; Tong, Y.; Singh, A.; Bertrand, A.; Lee, C. P.; Wang, D. S.; Bhattu, D.; Stefenelli, G.; Dave, J. S.; Puthussery, J. V.; Qi, L.; Vats, P.; Rai, P.; Casotto, R.; Satish, R.; Mishra, S.; Pospisilova, V.; Mohr, C.; Bell, D. M.; Ganguly, D.; Verma, V.; Rastogi, N.; Baltensperger, U.; Tripathi, S. N.; Prévôt, A. S. H.; Slowik, J. G. Highly Time-Resolved Chemical Speciation and Source Apportionment of Organic Aerosol Components in Delhi, India, Using Extractive Electrospray Ionization Mass Spectrometry. Atmos. Chem. Phys. 2022, 22, 7739– 7761,  DOI: 10.5194/acp-22-7739-2022
      19
      Highly time-resolved chemical speciation and source apportionment of organic aerosol components in Delhi, India, using extractive electrospray ionization mass spectrometry
      Kumar, Varun; Giannoukos, Stamatios; Haslett, Sophie L.; Tong, Yandong; Singh, Atinderpal; Bertrand, Amelie; Lee, Chuan Ping; Wang, Dongyu S.; Bhattu, Deepika; Stefenelli, Giulia; Dave, Jay S.; Puthussery, Joseph V.; Qi, Lu; Vats, Pawan; Rai, Pragati; Casotto, Roberto; Satish, Rangu; Mishra, Suneeti; Pospisilova, Veronika; Mohr, Claudia; Bell, David M.; Ganguly, Dilip; Verma, Vishal; Rastogi, Neeraj; Baltensperger, Urs; Tripathi, Sachchida N.; Prevot, Andre S. H.; Slowik, Jay G.
      Atmospheric Chemistry and Physics (2022), 22 (11), 7739-7761CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      In recent years, the Indian capital city of Delhi has been impacted by very high levels of air pollution, esp. during winter. Comprehensive knowledge of the compn. and sources of the org. aerosol (OA), which constitutes a substantial fraction of total particulate mass (PM) in Delhi, is central to formulating effective public health policies. Previous source apportionment studies in Delhi identified key sources of primary OA (POA) and showed that secondary OA (SOA) played a major role but were unable to resolve specific SOA sources. We address the latter through the first field deployment of an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) in Delhi, together with a high-resoln. aerosol mass spectrometer (AMS). Measurements were conducted during the winter of 2018/19, and pos. matrix factorization (PMF) was used sep. on AMS and EESI-TOF datasets to apportion the sources of OA. AMS PMF anal. yielded three primary and two secondary factors which were attributed to hydrocarbon-like OA (HOA), biomass burning OA (BBOA-1 and BBOA-2), more oxidized oxygenated OA (MO-OOA), and less oxidized oxygenated OA (LO-OOA). On av., 40% of the total OA mass was apportioned to the secondary factors. The SOA contribution to total OA mass varied greatly between the daytime (76.8%, 10:00-16:00 local time (LT)) and nighttime (31.0%, 21:00-04:00 LT). The higher chem. resoln. of EESI-TOF data allowed identification of individual SOA sources. The EESI-TOF PMF anal. in total yielded six factors, two of which were primary factors (primary biomass burning and cooking-related OA). The remaining four factors were predominantly of secondary origin: arom. SOA, biogenic SOA, aged biomass burning SOA, and mixed urban SOA. Due to the uncertainties in the EESI-TOF ion sensitivities, mass concns. of EESI-TOF SOA-dominated factors were related to the total AMS SOA (i.e. MO-OOA + LO-OOA) by multiple linear regression (MLR). Arom. SOA was the major SOA component during the daytime, with a 55.2% contribution to total SOA mass (42.4% contribution to total OA). Its contribution to total SOA, however, decreased to 25.4% (7.9% of total OA) during the nighttime. This factor was attributed to the oxidn. of light arom. compds. emitted mostly from traffic. Biogenic SOA accounted for 18.4% of total SOA mass (14.2% of total OA) during the daytime and 36.1% of total SOA mass (11.2% of total OA) during the nighttime. Aged biomass burning and mixed urban SOA accounted for 15.2% and 11.0% of total SOA mass (11.7% and 8.5% of total OA mass), resp., during the daytime and 15.4% and 22.9% of total SOA mass (4.8% and 7.1% of total OA mass), resp., during the nighttime. A simple diln.-partitioning model was applied on all EESI-TOF factors to est. the fraction of obsd. daytime concns. resulting from local photochem. prodn. (SOA) or emissions (POA). Arom. SOA, aged biomass burning, and mixed urban SOA were all found to be dominated by local photochem. prodn., likely from the oxidn. of locally emitted volatile org. compds. (VOCs). In contrast, biogenic SOA was related to the oxidn. of diffuse regional emissions of isoprene and monoterpenes. The findings of this study show that in Delhi, the nighttime high concns. are caused by POA emissions led by traffic and biomass burning and the daytime OA is dominated by SOA, with arom. SOA accounting for the largest fraction. Because arom. SOA is possibly more toxic than biogenic SOA and primary OA, its dominance during the daytime suggests an increased OA toxicity and health-related consequences for the general public.
    20. 20
      Finlayson-Pitts, B. J.; Pitts, J. N. CHAPTER 6 - Rates and Mechanisms of Gas-Phase Reactions in Irradiated Organic – NOx – Air Mixtures. In Chemistry of the Upper and Lower Atmosphere; Finlayson-Pitts, B. J., Pitts, J. N., Eds.; Academic Press: San Diego, 2000, pp 179– 263. DOI: 10.1016/B978-012257060-5/50008-3 .
      There is no corresponding record for this reference.
    21. 21
      Hallquist, M.; Wenger, J. C.; Baltensperger, U.; Rudich, Y.; Simpson, D.; Claeys, M.; Dommen, J.; Donahue, N. M.; George, C.; Goldstein, A. H.; Hamilton, J. F.; Herrmann, H.; Hoffmann, T.; Iinuma, Y.; Jang, M.; Jenkin, M. E.; Jimenez, J. L.; Kiendler-Scharr, A.; Maenhaut, W.; McFiggans, G.; Mentel, T. F.; Monod, A.; Prévôt, A. S. H.; Seinfeld, J. H.; Surratt, J. D.; Szmigielski, R.; Wildt, J. The Formation, Properties and Impact of Secondary Organic Aerosol: Current and Emerging Issues. Atmos. Chem. Phys. 2009, 9, 5155– 5236,  DOI: 10.5194/acp-9-5155-2009
      21
      The formation, properties and impact of secondary organic aerosol: current and emerging issues
      Hallquist, M.; Wenger, J. C.; Baltensperger, U.; Rudich, Y.; Simpson, D.; Claeys, M.; Dommen, J.; Donahue, N. M.; George, C.; Goldstein, A. H.; Hamilton, J. F.; Herrmann, H.; Hoffmann, T.; Iinuma, Y.; Jang, M.; Jenkin, M. E.; Jimenez, J. L.; Kiendler-Scharr, A.; Maenhaut, W.; McFiggans, G.; Mentel, Th. F.; Monod, A.; Prevot, A. S. H.; Seinfeld, J. H.; Surratt, J. D.; Szmigielski, R.; Wildt, J.
      Atmospheric Chemistry and Physics (2009), 9 (14/2), 5155-5236CODEN: ACPTCE; ISSN:1680-7316. (Copernicus Publications)
      A review. Secondary org. aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atm. processes, climate and human health. The chem. and phys. processes assocd. with SOA formation are complex and varied, and, despite considerable progress in recent years, a quant. and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atm. science. This review begins with an update on the current state of knowledge on the global SOA budget and is followed by an overview of the atm. degrdn. mechanisms for SOA precursors, gas-particle partitioning theory and the anal. techniques used to det. the chem. compn. of SOA. A survey of recent lab., field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail: mol. characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atm. org. components with sulfuric acid, the chem. and photochem. processing of orgs. in the atm. aq. phase, aerosol formation from real plant emissions, interaction of atm. org. components with water, thermodn. and mixts. in atm. models. Finally, the major challenges ahead in lab., field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.
    22. 22
      Calvert, J. G. The Mechanisms of Atmospheric Oxidation of Aromatic Hydrocarbons; Oxford University Press., 2002.
      There is no corresponding record for this reference.
    23. 23
      Bianchi, F.; Kurtén, T.; Riva, M.; Mohr, C.; Rissanen, M. P.; Roldin, P.; Berndt, T.; Crounse, J. D.; Wennberg, P. O.; Mentel, T. F.; Wildt, J.; Junninen, H.; Jokinen, T.; Kulmala, M.; Worsnop, D. R.; Thornton, J. A.; Donahue, N.; Kjaergaard, H. G.; Ehn, M. Highly Oxygenated Organic Molecules (HOM) from Gas-Phase Autoxidation Involving Peroxy Radicals: A Key Contributor to Atmospheric Aerosol. Chem. Rev. 2019, 119, 3472– 3509,  DOI: 10.1021/acs.chemrev.8b00395
      23
      Highly Oxygenated Molecules (HOM) from Gas-Phase Autoxidation Involving Organic Peroxy Radicals: A Key Contributor to Atmospheric Aerosol
      Bianchi, Federico; Kurten, Theo; Riva, Matthieu; Mohr, Claudia; Rissanen, Matti P.; Roldin, Pontus; Berndt, Torsten; Crounse, John D.; Wennberg, Paul O.; Mentel, Thomas F.; Wildt, Jurgen; Junninen, Heikki; Jokinen, Tuija; Kulmala, Markku; Worsnop, Douglas R.; Thornton, Joel A.; Donahue, Neil; Kjaergaard, Henrik G.; Ehn, Mikael
      Chemical Reviews (Washington, DC, United States) (2019), 119 (6), 3472-3509CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review which defines highly oxygenated org. mols. (HOM) formed in the atm. via auto-oxidn. involving peroxy radicals arising from volatile org. compds. describing currently available techniques for their identification/quantification, followed by a summary of the current knowledge on their formation mechanisms and physicochem. properties, is given. Major aims are to provide a common frame for the currently quite fragmented literature on HOM studies and highlighting existing gaps, and suggesting directions for future HOM research. Topics discussed include: introduction; HOM background (defining key concepts, HOM in relation to other classification schemes, historical naming conventions); HOM detection (gas and particle phases, uncertainties and anal. challenges of HOM detection); HOM formation mechanisms (auto-oxidn. involving peroxy radical as HOM source, bimol. RO2 reactions, factors affecting HOM formation); HOM properties and atm. fate (physicochem. properties, removal mechanisms); HOM atm. observations and impact (ambient HOM observation, atm. impact); and summary and perspectives.
    24. 24
      Crounse, J. D.; Nielsen, L. B.; Jørgensen, S.; Kjaergaard, H. G.; Wennberg, P. O. Autoxidation of Organic Compounds in the Atmosphere. J. Phys. Chem. Lett. 2013, 4, 3513– 3520,  DOI: 10.1021/jz4019207
      24
      Autoxidation of Organic Compounds in the Atmosphere
      Crounse, John D.; Nielsen, Lasse B.; Joergensen, Solvejg; Kjaergaard, Henrik G.; Wennberg, Paul O.
      Journal of Physical Chemistry Letters (2013), 4 (20), 3513-3520CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      A hypothesis that auto-oxidn. (inter- and intra-mol. H abstraction by peroxy radicals) plays an important role in the atm. oxidn. of org. compds., particularly org. matter assocd. with aerosols, is discussed. The rate of this process at room temp. was detd. in the lab. for a model compd., 3-pentanone. Ab-initio calcns. assessed H-shifts within a broader group of substituted org. compds. The rate of H abstraction by peroxy radicals was largely detd. by the thermochem. of nascent alkyl radicals; thus, it was highly affected by neighboring substituents. As a result, auto-oxidn. rates increased rapidly as O-contg. functional groups (carbonyl, hydroxy, hydroperoxy) are added to org. compds. This mechanism was consistent with formation of the multi-functional hydroperoxides and carbonyls often obsd. in atm. aerosol particles.
    25. 25
      Jokinen, T.; Sipilä, M.; Richters, S.; Kerminen, V.-M.; Paasonen, P.; Stratmann, F.; Worsnop, D.; Kulmala, M.; Ehn, M.; Herrmann, H.; Berndt, T. Rapid Autoxidation Forms Highly Oxidized RO2 Radicals in the Atmosphere. Angew. Chem., Int. Ed. 2014, 53, 14596– 14600,  DOI: 10.1002/anie.201408566
      25
      Rapid Autoxidation Forms Highly Oxidized RO2 Radicals in the Atmosphere
      Jokinen, Tuija; Sipilae, Mikko; Richters, Stefanie; Kerminen, Veli-Matti; Paasonen, Pauli; Stratmann, Frank; Worsnop, Douglas; Kulmala, Markku; Ehn, Mikael; Herrmann, Hartmut; Berndt, Torsten
      Angewandte Chemie, International Edition (2014), 53 (52), 14596-14600CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Gas-phase oxidn. routes of biogenic emissions, mainly isoprene and monoterpenes, in the atm. are still the subject of intensive research with special attention being paid to the formation of aerosol constituents. This lab. study shows that the most abundant monoterpenes (limonene and α-pinene) form highly oxidized RO2 radicals with up to 12 O atoms, along with related closed-shell products, within a few seconds after the initial attack of ozone or OH radicals. The overall process, an intramol. ROO→QOOH reaction and subsequent O2 addn. generating a next R'OO radical, is similar to the well-known autoxidn. processes in the liq. phase (QOOH stands for a hydroperoxyalkyl radical). Field measurements show the relevance of this process to atm. chem. Thus, the well-known reaction principle of autoxidn. is also applicable to the atm. gas-phase oxidn. of hydrocarbons leading to extremely low-volatility products which contribute to org. aerosol mass and hence influence the aerosol-cloud-climate system.
    26. 26
      Molteni, U.; Simon, M.; Heinritzi, M.; Hoyle, C. R.; Bernhammer, A.-K.; Bianchi, F.; Breitenlechner, M.; Brilke, S.; Dias, A.; Duplissy, J.; Frege, C.; Gordon, H.; Heyn, C.; Jokinen, T.; Kürten, A.; Lehtipalo, K.; Makhmutov, V.; Petäjä, T.; Pieber, S. M.; Praplan, A. P.; Schobesberger, S.; Steiner, G.; Stozhkov, Y.; Tomé, A.; Tröstl, J.; Wagner, A. C.; Wagner, R.; Williamson, C.; Yan, C.; Baltensperger, U.; Curtius, J.; Donahue, N. M.; Hansel, A.; Kirkby, J.; Kulmala, M.; Worsnop, D. R.; Dommen, J. Formation of Highly Oxygenated Organic Molecules from α-Pinene Ozonolysis: Chemical Characteristics, Mechanism, and Kinetic Model Development. ACS Earth Space Chem. 2019, 3, 873– 883,  DOI: 10.1021/acsearthspacechem.9b00035
      26
      Formation of Highly Oxygenated Organic Molecules from α-Pinene Ozonolysis: Chemical Characteristics, Mechanism, and Kinetic Model Development
      Molteni, Ugo; Simon, Mario; Heinritzi, Martin; Hoyle, Christopher R.; Bernhammer, Anne-Kathrin; Bianchi, Federico; Breitenlechner, Martin; Brilke, Sophia; Dias, Antonio; Duplissy, Jonathan; Frege, Carla; Gordon, Hamish; Heyn, Claudia; Jokinen, Tuija; Kurten, Andreas; Lehtipalo, Katrianne; Makhmutov, Vladimir; Petaja, Tuukka; Pieber, Simone M.; Praplan, Arnaud P.; Schobesberger, Siegfried; Steiner, Gerhard; Stozhkov, Yuri; Tome, Antonio; Trostl, Jasmin; Wagner, Andrea C.; Wagner, Robert; Williamson, Christina; Yan, Chao; Baltensperger, Urs; Curtius, Joachim; Donahue, Neil M.; Hansel, Armin; Kirkby, Jasper; Kulmala, Markku; Worsnop, Douglas R.; Dommen, Josef
      ACS Earth and Space Chemistry (2019), 3 (5), 873-883CODEN: AESCCQ; ISSN:2472-3452. (American Chemical Society)
      Terpenes are emitted by vegetation, and their oxidn. in the atm. is an important source of secondary org. aerosol (SOA). A part of this oxidn. can proceed through an autoxidn. process, yielding highly oxygenated org. mols. (HOMs) with low satn. vapor pressure. They can therefore contribute, even in the absence of sulfuric acid, to new particle formation (NPF). The understanding of the autoxidn. mechanism and its kinetics is still far from complete. Here, we present a mechanistic and kinetic anal. of mass spectrometry data from α-pinene (AP) ozonolysis expts. performed during the CLOUD 8 campaign at CERN. We grouped HOMs in classes according to their identified chem. compn. and investigated the relative changes of these groups and their components as a function of the reagent concn. We detd. reaction rate consts. for the different HOM peroxy radical reaction pathways. The accretion reaction between HOM peroxy radicals was found to be extremely fast. We developed a pseudo-mechanism for HOM formation and added it to the AP oxidn. scheme of the Master Chem. Mechanism (MCM). With this extended model, the obsd. concns. and trends in HOM formation were successfully simulated.
    27. 27
      Surratt, J. D.; Chan, A. W. H.; Eddingsaas, N. C.; Chan, M.; Loza, C. L.; Kwan, A. J.; Hersey, S. P.; Flagan, R. C.; Wennberg, P. O.; Seinfeld, J. H. Reactive Intermediates Revealed in Secondary Organic Aerosol Formation from Isoprene. Proc. Natl. Acad. Sci. U.S.A. 2010, 107, 6640– 6645,  DOI: 10.1073/pnas.0911114107
      27
      Reactive intermediates revealed in secondary organic aerosol formation from isoprene
      Surratt, Jason D.; Chan, Arthur W. H.; Eddingsaas, Nathan C.; Chan, Mannin; Loza, Christine L.; Kwan, Alan J.; Hersey, Scott P.; Flagan, Richard C.; Wennberg, Paul O.; Seinfeld, John H.
      Proceedings of the National Academy of Sciences of the United States of America (2010), 107 (15), 6640-6645, S6640/1-S6640/10CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
      Isoprene is a significant source of atm. org. aerosol; however, the oxidn. pathways that lead to secondary org. aerosol (SOA) have remained elusive. Here, we identify the role of two key reactive intermediates, epoxydiols of isoprene (IEPOX = β-IEPOX + δ-IEPOX) and methacryloylperoxynitrate (MPAN), which are formed during isoprene oxidn. under low- and high-NOx conditions, resp. Isoprene low-NOx SOA is enhanced in the presence of acidified sulfate seed aerosol (mass yield 28.6%) over that in the presence of neutral aerosol (mass yield 1.3%). Increased uptake of IEPOX by acid-catalyzed particle-phase reactions is shown to explain this enhancement. Under high-NOx conditions, isoprene SOA formation occurs through oxidn. of its second-generation product, MPAN. The similarity of the compn. of SOA formed from the photooxidn. of MPAN to that formed from isoprene and methacrolein demonstrates the role of MPAN in the formation of isoprene high-NOx SOA. Reactions of IEPOX and MPAN in the presence of anthropogenic pollutants (i.e., acidic aerosol produced from the oxidn. of SO2 and NO2, resp.) could be a substantial source of "missing urban SOA" not included in current atm. models.
    28. 28
      Pospisilova, V.; Lopez-Hilfiker, F. D.; Bell, D. M.; El Haddad, I.; Mohr, C.; Huang, W.; Heikkinen, L.; Xiao, M.; Dommen, J.; Prevot, A. S. H.; Baltensperger, U.; Slowik, J. G. On the Fate of Oxygenated Organic Molecules in Atmospheric Aerosol Particles. Sci. Adv. 2020, 6(). DOI: 10.1126/sciadv.aax8922 .
      There is no corresponding record for this reference.
    29. 29
      Bell, D. M.; Wu, C.; Bertrand, A.; Graham, E. L.; Schoonbaert, J.; Giannoukos, S.; Baltensperger, U.; Prevot, A. S. H.; Riipinen, I.; El Haddad, I.; Mohr, C. Particle-phase processing of α-pinene NO3 secondary organic aerosol in the dark. Atmos. Chem. Phys. 2022, 22, 13167– 13182,  DOI: 10.5194/acp-22-13167-2022
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      Particle-phase processing of α-pinene NO3 secondary organic aerosol in the dark
      Bell, David M.; Wu, Cheng; Bertrand, Amelie; Graham, Emelie; Schoonbaert, Janne; Giannoukos, Stamatios; Baltensperger, Urs; Prevot, Andre S. H.; Riipinen, Ilona; El Haddad, Imad; Mohr, Claudia
      Atmospheric Chemistry and Physics (2022), 22 (19), 13167-13182CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      The NO3 radical represents a significant night time oxidant which is present downstream of polluted environments. Existing studies have investigated the formation of secondary org. aerosol (SOA) from NO3 radicals, focusing on the yields, general compn., and hydrolysis of organonitrates; however, there is limited knowledge about how the compn. of NO3-derived SOA evolves as a result of particle-phase reactions. Here, SOA was formed from the reaction of α-pinene with NO3 radicals generated from N2O5, and the resulting SOA was aged in the dark. The initial compn. of NO3-derived α-pinene SOA was slightly dependent upon the concn. of N2O5 injected (excess of NO3 or excess of α-pinene) but was largely dominated by dimer dinitrates (C20H32N2O8-13). Oxidn. reactions (e.g., C20H32N2O8 → C20H32N2O9 → C20H32N2O10) accounted for 60 %-70 % of the particle-phase reactions obsd. Fragmentation reactions and dimer degrdn. pathways made up the remainder of the particle-phase processes occurring. The exact oxidant is not known, although suggestions are offered (e.g., N2O5, org. peroxides, or peroxynitrates). Hydrolysis of -ONO2 functional groups was not an important loss term during dark aging under the relative humidity conditions of our expts. (58 %-62 %), and changes in the bulk organonitrate compn. were likely driven by evapn. of highly nitrogenated mols. Overall, 25 %-30 % of the particle-phase compn. changes as a function of particle-phase reactions during dark aging, representing an important atm. aging pathway.
    30. 30
      Krapf, M.; El Haddad, I.; Bruns, E. A.; Molteni, U.; Daellenbach, K. R.; Prévôt, A. S. H.; Baltensperger, U.; Dommen, J. Labile Peroxides in Secondary Organic Aerosol. Chem 2016, 1, 603– 616,  DOI: 10.1016/j.chempr.2016.09.007
      30
      Labile Peroxides in Secondary Organic Aerosol
      Krapf, Manuel; El Haddad, Imad; Bruns, Emily A.; Molteni, Ugo; Daellenbach, Kaspar R.; Prevot, Andre S. H.; Baltensperger, Urs; Dommen, Josef
      Chem (2016), 1 (4), 603-616CODEN: CHEMVE; ISSN:2451-9294. (Cell Press)
      Peroxide-contg. highly oxygenated mols. (HOMs) are formed upon ozonolysis of terpenes emitted from the biosphere and are expected to be a major driving force for the formation of new particles and secondary org. aerosol (SOA) in the atm. We evaluate and model the contribution of org. peroxides to α-pinene SOA and their evolution under different conditions. We det. a HOM molar yield of ∼5%, contributing 30% to the initial SOA mass. Although the formation of these compds. is kinetically favored, we demonstrate that they are thermodynamically unstable with half-lives shorter than 1 h under dark conditions. Their decompn. significantly alters SOA chem. compn., volatility, and oxidn. state. We show that photolysis of carbonyls occurring within a timescale of hours is an efficient but largely overlooked mechanism by which SOA may evolve in the atm. Both of these pathways add to a better understanding of the aerosol-climate interaction and the health effects of SOA.
    31. 31
      Zhang, Z.-H.; Hartner, E.; Utinger, B.; Gfeller, B.; Paul, A.; Sklorz, M.; Czech, H.; Yang, B. X.; Su, X. Y.; Jakobi, G.; Orasche, J.; Schnelle-Kreis, J.; Jeong, S.; Gröger, T.; Pardo, M.; Hohaus, T.; Adam, T.; Kiendler-Scharr, A.; Rudich, Y.; Zimmermann, R.; Kalberer, M. Are Reactive Oxygen Species (ROS) a Suitable Metric to Predict Toxicity of Carbonaceous Aerosol Particles?. Atmos. Chem. Phys. 2022, 22, 1793– 1809,  DOI: 10.5194/acp-22-1793-2022
      31
      Are reactive oxygen species (ROS) a suitable metric to predict toxicity of carbonaceous aerosol particles?
      Zhang, Zhi-Hui; Hartner, Elena; Utinger, Battist; Gfeller, Benjamin; Paul, Andreas; Sklorz, Martin; Czech, Hendryk; Yang, Bin Xia; Su, Xin Yi; Jakobi, Gert; Orasche, Jurgen; Schnelle-Kreis, Jurgen; Jeong, Seongho; Groger, Thomas; Pardo, Michal; Hohaus, Thorsten; Adam, Thomas; Kiendler-Scharr, Astrid; Rudich, Yinon; Zimmermann, Ralf; Kalberer, Markus
      Atmospheric Chemistry and Physics (2022), 22 (3), 1793-1809CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      It is being suggested that particle-bound or particle-induced reactive oxygen species (ROS), which significantly contribute to the oxidative potential (OP) of aerosol particles, are a promising metric linking aerosol compns. to toxicity and adverse health effects. However, accurate ROS quantification remains challenging due to the reactive and short-lived nature of many ROS components and the lack of appropriate anal. methods for a reliable quantification. Consequently, it remains difficult to gauge their impact on human health, esp. to identify how aerosol particle sources and atm. processes drive particle-bound ROS formation in a real-world urban environment. In this study, using a novel online particle-bound ROS instrument (OPROSI), we comprehensively characterized and compared the formation of ROS in secondary org. aerosols (SOAs) generated from org. compds. that represent anthropogenic (naphthalene, SOANAP) and biogenic (β-pinene, SOAβPIN) precursors. The SOA mass was condensed onto soot particles (SP) under varied atmospherically relevant conditions (photochem. aging and humidity) to mimic the SOA formation from a mixing of traffic-related carbonaceous primary aerosols and volatile org. compds. (VOCs). We systematically analyzed the ability of the aq. exts. of the two aerosol types (SOANAP-SP and SOAβPIN-SP) to induce ROS prodn. and OP. We further investigated cytotoxicity and cellular ROS prodn. after exposing human lung epithelial cell cultures (A549) to exts. of the two aerosols. A significant finding of this study is that more than 90% of all ROS components in both SOA types have a short lifetime, highlighting the need to develop online instruments for a meaningful quantification of ROS. Our results also show that photochem. aging promotes particle-bound ROS prodn. and enhances the OP of the aerosols. Compared to SOAβPIN-SP, SOANAP-SP elicited a higher acellular and cellular ROS prodn., a higher OP, and a lower cell viability. These consistent results between chem.-based and biol.-based analyses indicate that particle-bound ROS quantification could be a feasible metric to predict aerosol particle toxicity and adverse human effects. Moreover, the cellular ROS prodn. caused by SOA exposure not only depends on aerosol type but is also affected by exposure dose, highlighting a need to mimic the process of particle deposition onto lung cells and their interactions as realistically as possible to avoid unknown biases.
    32. 32
      Li, Y.; Zhao, J.; Wang, Y.; Seinfeld, J. H.; Zhang, R. Multigeneration Production of Secondary Organic Aerosol from Toluene Photooxidation. Environ. Sci. Technol. 2021, 55, 8592– 8603,  DOI: 10.1021/acs.est.1c02026
      32
      Multigeneration Production of Secondary Organic Aerosol from Toluene Photooxidation
      Li, Yixin; Zhao, Jiayun; Wang, Yuan; Seinfeld, John H.; Zhang, Renyi
      Environmental Science & Technology (2021), 55 (13), 8592-8603CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Photooxidn. of volatile org. compds. (VOCs) produces secondary org. aerosol (SOA) and light-absorbing brown carbon (BrC) via multiple reaction steps/pathways, reflecting significant chem. complexity relevant to gaseous oxidn. and subsequent gas-to-particle conversion. Toluene is an important VOC under urban conditions, but the fundamental chem. mechanism leading to SOA formation remains uncertain. Here, we elucidate multigeneration SOA prodn. from toluene by simultaneously tracking the evolutions of gas-phase oxidn. and aerosol formation in a reaction chamber. Large size increase and browning of monodisperse sub-micrometer seed particles occur shortly after initiating oxidn. by hydroxyl radical (OH) at 10-90% relative humidity (RH). The evolution in gaseous products and aerosol properties (size/d./optical properties) and chem. speciation of aerosol-phase products indicate that the aerosol growth and browning result from earlier generation products consisting dominantly of dicarbonyl and carboxylic functional groups. While volatile dicarbonyls engage in aq. reactions to yield nonvolatile oligomers and light-absorbing nitrogen heterocycles/heterochains (in the presence of NH3) at high RH, org. acids contribute to aerosol carboxylates via ionic dissocn. or acid-base reaction in a wide RH range. We conclude that toluene contributes importantly to SOA/BrC formation from dicarbonyls and org. acids because of their prompt and high yields from photooxidn. and unique functionalities for participation in aerosol-phase reactions.
    33. 33
      Mutzel, A.; Zhang, Y.; Böge, O.; Rodigast, M.; Kolodziejczyk, A.; Wang, X.; Herrmann, H. Importance of secondary organic aerosol formation of α-pinene, limonene, and m-cresol comparing day- and nighttime radical chemistry. Atmos. Chem. Phys. 2021, 21, 8479– 8498,  DOI: 10.5194/acp-21-8479-2021
      33
      Importance of secondary organic aerosol formation of α-pinene, limonene, and m-cresol comparing day- and nighttime radical chemistry
      Mutzel, Anke; Zhang, Yanli; Boege, Olaf; Rodigast, Maria; Kolodziejczyk, Agata; Wang, Xinming; Herrmann, Hartmut
      Atmospheric Chemistry and Physics (2021), 21 (11), 8479-8498CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      The oxidn. of biogenic and anthropogenic compds. leads to the formation of secondary org. aerosol mass (SOA). The present study aims to investigate α-pinene, limonene, and m-cresol with regards to their SOA formation potential dependent on relative humidity (RH) under night-(NO3 radicals) and daytime conditions (OH radicals) and the resulting chem. compn. It was found that SOA formation potential of limonene with NO3 under dry conditions significantly exceeds that of the OH-radical reaction, with SOA yields of 15-30%and 10-21%, resp. Addnl., the nocturnal SOA yield was found to be very sensitive towards RH, yielding more SOA under dry conditions. In contrast, the SOA formation potential of α-pinene with NO3 slightly exceeds that of the OH-radical reaction, independent from RH. On av., α-pinene yielded SOA with about 6-7% from NO3 radicals and 3-4% from OH-radical reaction. Surprisingly, unexpectedly high SOA yields were found for m-cresol oxidn. with OH radicals (3-9%), with the highest yield under elevated RH (9%), which is most likely attributable to a higher fraction of 3-methyl-6-nitro-catechol (MNC). While α-pinene and m-cresol SOA was found to be mainly composed of water-sol. compds., 50-68% of nocturnal SOA and 22-39% of daytime limonene SOA are water-insol. The fraction of SOA-bound peroxides which originated from α-pinene varied between 2 and 80% as a function of RH. Furthermore, SOA from α-pinene revealed pinonic acid as the most important particle-phase constituent under day- and nighttime conditions with a fraction of 1-4%. Other compds. detected are norpinonic acid (0.05-1.1% mass fraction), terpenylic acid (0.1-1.1% mass fraction), pinic acid (0.1-1.8% mass fraction), and 3-methyl-1,2,3-tricarboxylic acid (0.05-0.5% mass fraction). All marker compds. showed higher fractions under dry conditions when formed during daytime and showed almost no RH effect when formed during night.
    34. 34
      Zaytsev, A.; Koss, A. R.; Breitenlechner, M.; Krechmer, J. E.; Nihill, K. J.; Lim, C. Y.; Rowe, J. C.; Cox, J. L.; Moss, J.; Roscioli, J. R.; Canagaratna, M. R.; Worsnop, D. R.; Kroll, J. H.; Keutsch, F. N. Mechanistic Study of the Formation of Ring-Retaining and Ring-Opening Products from the Oxidation of Aromatic Compounds under Urban Atmospheric Conditions. Atmos. Chem. Phys. 2019, 19, 15117– 15129,  DOI: 10.5194/acp-19-15117-2019
      34
      Mechanistic study of the formation of ring-retaining and ring-opening products from the oxidation of aromatic compounds under urban atmospheric conditions
      Zaytsev, Alexander; Koss, Abigail R.; Breitenlechner, Martin; Krechmer, Jordan E.; Nihill, Kevin J.; Lim, Christopher Y.; Rowe, James C.; Cox, Joshua L.; Moss, Joshua; Roscioli, Joseph R.; Canagaratna, Manjula R.; Worsnop, Douglas R.; Kroll, Jesse H.; Keutsch, Frank N.
      Atmospheric Chemistry and Physics (2019), 19 (23), 15117-15129CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Arom. hydrocarbons make up a large fraction of anthropogenic volatile org. compds. and contribute significantly to the prodn. of tropospheric ozone and secondary org. aerosol (SOA). Four toluene and four 1,2,4-trimethylbenzene (1,2,4-TMB) photooxidn. expts. were performed in an environmental chamber under relevant polluted conditions (NOx ∼ 10 ppb). An extensive suite of instrumentation including two proton-transfer-reaction mass spectrometers (PTR-MS) and two chem. ionisation mass spectrometers (NH4+ CIMS and I-CIMS) allowed for quantification of reactive carbon in multiple generations of hydroxyl radical (OH)-initiated oxidn. Oxidn. of both species produces ring-retaining products such as cresols, benzaldehydes, and bicyclic intermediate compds., as well as ring-scission products such as epoxides and dicarbonyls. We report the elemental compn. of these compds. formed under relevant urban high-NO conditions. We show that ring-retaining products for these two precursors are more diverse and abundant than predicted by current mechanisms. We present the speciated elemental compn. of SOA for both precursors and confirm that highly oxygenated products make up a significant fraction of SOA. Ring-scission products are also detected in both the gas and particle phases, and their yields and speciation generally agree with the kinetic model prediction.
    35. 35
      Voliotis, A.; Wang, Y.; Shao, Y.; Du, M.; Bannan, T. J.; Percival, C. J.; Pandis, S. N.; Alfarra, M. R.; McFiggans, G. Exploring the composition and volatility of secondary organic aerosols in mixed anthropogenic and biogenic precursor systems. Atmos. Chem. Phys. 2021, 21, 14251– 14273,  DOI: 10.5194/acp-21-14251-2021
      35
      Exploring the composition and volatility of secondary organic aerosols in mixed anthropogenic and biogenic precursor systems
      Voliotis, Aristeidis; Wang, Yu; Shao, Yunqi; Du, Mao; Bannan, Thomas J.; Percival, Carl J.; Pandis, Spyros N.; Alfarra, M. Rami; McFiggans, Gordon
      Atmospheric Chemistry and Physics (2021), 21 (18), 14251-14273CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Secondary org. aerosol (SOA) formation from mixts. of volatile precursors may be influenced by the mol. interactions of the components of the mixt. Here, we report measurements of the volatility distribution of SOA formed from the photo-oxidn. of o-cresol, α-pinene, and their mixts., representative anthropogenic and biogenic precursors, in an atm. simulation chamber. The combination of two independent thermal techniques (thermal denuder, TD, and the Filter Inlet for Gases and Aerosols coupled to a high-resoln. time-of-flight chem. ionization mass spectrometer, FIGAERO-CIMS) to measure the particle volatility, along with detailed gas- and particle-phase compn. measurements, provides links between the chem. compn. of the mixt. and the resultant SOA particle volatility. The SOA particle volatility obtained by the two independent techniques showed substantial discrepancies. The particle volatility obtained by the TD was wider, spanning across the LVOC and SVOC range, while the resp. FIGAERO-CIMS derived using two different methods (i.e. calibrated Tmax and partitioning calcns.) was substantially higher (mainly in the SVOC and IVOC, resp.) and narrow. Although the quantification of the SOA particle volatility was challenging, both techniques and methods showed similar trends, with the volatility of the SOA formed from the photo-oxidn. of α-pinene being higher than that measured in the o-cresol system, while the volatility of the SOA particles of the mixt. was between those measured at the single-precursor systems. This behavior could be explained by two opposite effects, the scavenging of the larger mols. with lower volatility produced in the single-precursor expts. that led to an increase in the av. volatility and the formation of unique-to-the-mixt. products that had higher O:C, MW, [Formula Omitted] and, consequently, lower volatility compared to those derived from the individual precursors. We further discuss the potential limitations of FIGAERO-CIMS to report quant. volatilities and their implications for the reported results, and we show that the particle volatility changes can be qual. assessed, while caution should be taken when linking the chem. compn. to the particle volatility. These results present the first detailed observations of SOA particle volatility and compn. in mixed anthropogenic and biogenic systems and provide an anal. context that can be used to explore particle volatility in chamber expts.
    36. 36
      McFiggans, G.; Mentel, T. F.; Wildt, J.; Pullinen, I.; Kang, S.; Kleist, E.; Schmitt, S.; Springer, M.; Tillmann, R.; Wu, C.; Zhao, D.; Hallquist, M.; Faxon, C.; Le Breton, M.; Hallquist, Å. M.; Simpson, D.; Bergström, R.; Jenkin, M. E.; Ehn, M.; Thornton, J. A.; Alfarra, M. R.; Bannan, T. J.; Percival, C. J.; Priestley, M.; Topping, D.; Kiendler-Scharr, A. Secondary Organic Aerosol Reduced by Mixture of Atmospheric Vapours. Nature 2019, 565, 587– 593,  DOI: 10.1038/s41586-018-0871-y
      36
      Secondary organic aerosol reduced by mixture of atmospheric vapours
      McFiggans, Gordon; Mentel, Thomas F.; Wildt, Jurgen; Pullinen, Iida; Kang, Sungah; Kleist, Einhard; Schmitt, Sebastian; Springer, Monika; Tillmann, Ralf; Wu, Cheng; Zhao, Defeng; Hallquist, Mattias; Faxon, Cameron; Le Breton, Michael; Hallquist, Asa M.; Simpson, David; Bergstrom, Robert; Jenkin, Michael E.; Ehn, Mikael; Thornton, Joel A.; Alfarra, M. Rami; Bannan, Thomas J.; Percival, Carl J.; Priestley, Michael; Topping, David; Kiendler-Scharr, Astrid
      Nature (London, United Kingdom) (2019), 565 (7741), 587-593CODEN: NATUAS; ISSN:0028-0836. (Nature Research)
      Secondary org. aerosol (SOA) contributes to the atm. particulate burden with implications for air quality and climate. Biogenic volatile org. compds. (BVOC), e.g., plant-emitted terpenoids, are important SOA precursors with isoprene dominating BVOC emissions globally; however, the isoprene oxidn. particle mass is generally modest vs. other terpenoids. This work showed isoprene, CO, and CH4 can each suppress the instantaneous mass and overall mass yield derived from monoterpenes in atm. vapor mixts. Isoprene scavenges OH-, preventing their reaction with monoterpenes, and the resulting isoprene peroxy radicals scavenge highly oxygenated monoterpene products. These effects reduce the yield of low volatility products which would otherwise form SOA. Global model calcns. indicated oxidant and product scavenging can operate effectively in the atm. Thus, highly reactive compds. (e.g., isoprene) which produce a modest amt. of aerosol are not necessarily net producers of SOA particle mass and their oxidn. in atm. vapor mixts. can suppress particle no. and SOA mass. SOA atm. formation mechanisms should be considered more realistically to account for mechanistic interactions between products of oxidizing precursor mols. (recognized to be necessary when modeling O3 prodn.).
    37. 37
      Kramer, A. L.; Suski, K. J.; Bell, D. M.; Zelenyuk, A.; Massey Simonich, S. L. Formation of Polycyclic Aromatic Hydrocarbon Oxidation Products in α-Pinene Secondary Organic Aerosol Particles Formed through Ozonolysis. Environ. Sci. Technol. 2019, 53, 6669– 6677,  DOI: 10.1021/acs.est.9b01732
      37
      Formation of Polycyclic Aromatic Hydrocarbon Oxidation Products in α-Pinene Secondary Organic Aerosol Particles Formed through Ozonolysis
      Kramer, Amber L.; Suski, Kaitlyn J.; Bell, David M.; Zelenyuk, Alla; Massey Simonich, Staci L.
      Environmental Science & Technology (2019), 53 (12), 6669-6677CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Accurate long-range atm. transport (LRAT) modeling of polycyclic arom. hydrocarbons (PAH) and PAH oxidn. products (PAH-OP) in secondary org. aerosol (SOA) particles relies on particle known chem. compn. Four PAH (phenanthrene [PHE] dibenzothiophene [DBT], pyrene [PYR], benz(a)anthracene [BaA]), were studied individually to identify and quantify PAH-OP produced and incorporated into SOA particles formed by ozonolysis of α-pinene in the presence of PAH vapor. SOA particles, characterized by real-time in-situ instrumentation, were collected on quartz fiber filters for off-line PAH and PAH-OP analyses. PAH-OP were measured in all PAH expts. at equal or greater concns. than the individual PAH they were produced from. Total PAH and PAH-OP mass relative to total SOA mass varied for different expts. on individual parent PAH: PHE and 6 quantified PHE-OP (3.0%); DBT and dibenzothiophene sulfone (4.9%); PYR and 3 quantified PYR-OP (3.1%); and BaA and benz(a)anthracene-7,12-dione (0.26%). Further exposure of PAH-SOA to O3 generally increased PAH-OP:PAH concn. ratios, suggesting longer atm. lifetimes for PAH-OP vs. PAH. These data indicated PAH-OP are formed during SOA particle formation and growth.
    38. 38
      Zelenyuk, A.; Imre, D. G.; Wilson, J.; Bell, D. M.; Suski, K. J.; Shrivastava, M.; Beránek, J.; Alexander, M. L.; Kramer, A. L.; Massey Simonich, S. L. The Effect of Gas-Phase Polycyclic Aromatic Hydrocarbons on the Formation and Properties of Biogenic Secondary Organic Aerosol Particles. Faraday Discuss. 2017, 200, 143– 164,  DOI: 10.1039/C7FD00032D
      38
      The effect of gas-phase polycyclic aromatic hydrocarbons on the formation and properties of biogenic secondary organic aerosol particles
      Zelenyuk, Alla; Imre, Dan G.; Wilson, Jacqueline; Bell, David M.; Suski, Kaitlyn J.; Shrivastava, Manish; Beranek, Josef; Alexander, M. Lizabeth; Kramer, Amber L.; Massey Simonich, Staci L.
      Faraday Discussions (2017), 200 (Atomospheric Chemistry in the Anthropocene), 143-164CODEN: FDISE6; ISSN:1359-6640. (Royal Society of Chemistry)
      When secondary org. aerosol (SOA) particles are formed by ozonolysis in the presence of gas-phase polycyclic arom. hydrocarbons (PAHs), their formation and properties are significantly different from SOA particles formed without PAHs. For all SOA precursors and all PAHs, discussed in this study, the presence of the gas-phase PAHs during SOA formation significantly affects particle mass loadings, compn., growth, evapn. kinetics, and viscosity. SOA particles formed in the presence of PAHs have, as part of their compns., trapped unreacted PAHs and products of heterogeneous reactions between PAHs and ozone. Compared to 'pure' SOA particles, these particles exhibit slower evapn. kinetics, have higher fractions of non-volatile components, like oligomers, and higher viscosities, assuring their longer atm. lifetimes. In turn, the increased viscosity and decreased volatility provide a shield that protects PAHs from chem. degrdn. and evapn., allowing for the long-range transport of these toxic pollutants. The magnitude of the effect of PAHs on SOA formation is surprisingly large. The presence of PAHs during SOA formation increases mass loadings by factors of two to five, and particle no. concns., in some cases, by more than a factor of 100. Increases in SOA mass, particle no. concns., and lifetime have important implications to many atm. processes related to climate, weather, visibility, and human health, all of which relate to the interactions between biogenic SOA and anthropogenic PAHs. The synergistic relationship between SOA and PAHs presented here are clearly complex and call for future research to elucidate further the underlying processes and their exact atm. implications.
    39. 39
      Shrivastava, M.; Cappa, C. D.; Fan, J.; Goldstein, A. H.; Guenther, A. B.; Jimenez, J. L.; Kuang, C.; Laskin, A.; Martin, S. T.; Ng, N. L.; Petaja, T.; Pierce, J. R.; Rasch, P. J.; Roldin, P.; Seinfeld, J. H.; Shilling, J.; Smith, J. N.; Thornton, J. A.; Volkamer, R.; Wang, J.; Worsnop, D. R.; Zaveri, R. A.; Zelenyuk, A.; Zhang, Q. Recent Advances in Understanding Secondary Organic Aerosol: Implications for Global Climate Forcing. Rev. Geophys. 2017, 55, 509– 559,  DOI: 10.1002/2016RG000540
      There is no corresponding record for this reference.
    40. 40
      Platt, S. M.; El Haddad, I.; Zardini, A. A.; Clairotte, M.; Astorga, C.; Wolf, R.; Slowik, J. G.; Temime-Roussel, B.; Marchand, N.; Ježek, I.; Drinovec, L.; Močnik, G.; Möhler, O.; Richter, R.; Barmet, P.; Bianchi, F.; Baltensperger, U.; Prévôt, A. S. H. Secondary Organic Aerosol Formation from Gasoline Vehicle Emissions in a New Mobile Environmental Reaction Chamber. Atmos. Chem. Phys. 2013, 13, 9141– 9158,  DOI: 10.5194/acp-13-9141-2013
      40
      Secondary organic aerosol formation from gasoline vehicle emissions in a new mobile environmental reaction chamber
      Platt, S. M.; El Haddad, I.; Zardini, A. A.; Clairotte, M.; Astorga, C.; Wolf, R.; Slowik, J. G.; Temime-Roussel, B.; Marchand, N.; Jezek, I.; Drinovec, L.; Mocnik, G.; Moehler, O.; Richter, R.; Barmet, P.; Bianchi, F.; Baltensperger, U.; Prevot, A. S. H.
      Atmospheric Chemistry and Physics (2013), 13 (18), 9141-9158, 18 pp.CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      We present a new mobile environmental reaction chamber for the simulation of the atm. aging of different emission sources without limitation from the instruments or facilities available at any single site. Photochem. is simulated using a set of 40 UV lights (total power 4 KW). Characterization of the emission spectrum of these lights shows that atm. aging of emissions may be simulated over a range of temps. (-7 to 25 °C). A photolysis rate of NO2, JNO2, of (8.0 ± 0.7) × 10-3 s-1 was detd. at 25°C. We demonstrate the utility of this new system by presenting results on the aging (OH = 12 × 106 cm-3 h) of emissions from a modern (Euro 5) gasoline car operated during a driving cycle (New European Driving Cycle, NEDC) on a chassis dynamometer in a vehicle test cell. Emissions from the entire NEDC were sampled and aged in the chamber. Total org. aerosol (OA; primary org. aerosol (POA) emission + secondary org. aerosol (SOA) formation) was (369.8-397.5) 10-3 g kg-1 fuel, or (13.2-15.4) × 10-3 g km-1, after aging, with aged OA/POA in the range 9-15. A thorough investigation of the compn. of the gas phase emissions suggests that the obsd. SOA is from previously unconsidered precursors and processes. This large enhancement in particulate matter mass from gasoline vehicle aerosol emissions due to SOA formation, if it occurs across a wider range of gasoline vehicles, would have significant implications for our understanding of the contribution of on-road gasoline vehicles to ambient aerosols.
    41. 41
      DeCarlo, P. F.; Kimmel, J. R.; Trimborn, A.; Northway, M. J.; Jayne, J. T.; Aiken, A. C.; Gonin, M.; Fuhrer, K.; Horvath, T.; Docherty, K. S.; Worsnop, D. R.; Jimenez, J. L. Field-Deployable, High-Resolution, Time-of-Flight Aerosol Mass Spectrometer. Anal. Chem. 2006, 78, 8281– 8289,  DOI: 10.1021/ac061249n
      41
      Field-Deployable, High-Resolution, Time-of-Flight Aerosol Mass Spectrometer
      DeCarlo, Peter F.; Kimmel, Joel R.; Trimborn, Achim; Northway, Megan J.; Jayne, John T.; Aiken, Allison C.; Gonin, Marc; Fuhrer, Katrin; Horvath, Thomas; Docherty, Kenneth S.; Worsnop, Doug R.; Jimenez, Jose L.
      Analytical Chemistry (2006), 78 (24), 8281-8289CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
      Development of a new, high-resoln. time-of-flight aerosol mass spectrometer (HR-ToF-AMS) is reported. High-resoln. capability of this instrument allows direct sepn. of most org. and inorg. ions at the same nominal m/z, quantification of several types of org. fragments (CxHy, CxHyOz, CxHyNp, CxHyOzNp), and direct identification of org. N and organo-S content. This real-time instrument is field-deployable and its high time resoln. (0.5 Hz was demonstrated) makes it well-suited for studies in which time resoln. is crit., e.g., aircraft studies. The instrument has 2 ion optical modes: a single-reflection configuration offering higher sensitivity and lower resolving power (≤∼2100 at m/z 200); and a 2-reflectron configuration yielding higher resolving power (≤∼4300 at m/z 200) with lower sensitivity. It also detns. the size distribution of all ions. One-minute detection limits for sub-micrometer aerosol was <0.04 μg/m3 for all species in high-sensitivity mode and <0.4 μg/m3 in high-resoln. mode. Examples of ambient aerosol data are presented from the SOAR-1 study in Riverside, California, in which ambient org. species spectra were dominated by CxHy and CxHyOz fragments; different org. and inorg. fragments at the same nominal m/z showed different size distributions. Data are also presented from the MIRAGE C-130 aircraft study near Mexico City, Mexico, showing high correlation with independent measurements of surrogate aerosol mass concn.
    42. 42
      Canagaratna, M. R.; Jayne, J. T.; Jimenez, J. L.; Allan, J. D.; Alfarra, M. R.; Zhang, Q.; Onasch, T. B.; Drewnick, F.; Coe, H.; Middlebrook, A.; Delia, A.; Williams, L. R.; Trimborn, A. M.; Northway, M. J.; DeCarlo, P. F.; Kolb, C. E.; Davidovits, P.; Worsnop, D. R. Chemical and Microphysical Characterization of Ambient Aerosols with the Aerodyne Aerosol Mass Spectrometer. Mass Spectrom. Rev. 2007, 26, 185– 222,  DOI: 10.1002/mas.20115
      42
      Chemical and microphysical characterization of ambient aerosols with the aerodyne aerosol mass spectrometer
      Canagaratna, M. R.; Jayne, J. T.; Jimenez, J. L.; Allan, J. D.; Alfarra, M. R.; Zhang, Q.; Onasch, T. B.; Drewnick, F.; Coe, H.; Middlebrook, A.; Delia, A.; Williams, L. R.; Trimborn, A. M.; Northway, M. J.; DeCarlo, P. F.; Kolb, C. E.; Davidovits, P.; Worsnop, D. R.
      Mass Spectrometry Reviews (2007), 26 (2), 185-222CODEN: MSRVD3; ISSN:0277-7037. (John Wiley & Sons, Inc.)
      A review. The application of mass spectrometric techniques to the real-time measurement and characterization of aerosols represents a significant advance in the field of atm. science. This review focuses on the aerosol mass spectrometer (AMS), an instrument designed and developed at Aerodyne Research, Inc. (ARI) that is the most widely used thermal vaporization AMS. The AMS uses aerodynamic lens inlet technol. together with thermal vaporization and electron-impact mass spectrometry to measure the real-time non-refractory (NR) chem. speciation and mass loading as a function of particle size of fine aerosol particles with aerodynamic diams. between ∼50 and 1,000 nm. The original AMS utilizes a quadrupole mass spectrometer (Q) with electron impact (EI) ionization and produces ensemble av. data of particle properties. Later versions employ time-of-flight (ToF) mass spectrometers and can produce full mass spectral data for single particles. This manuscript presents a detailed discussion of the strengths and limitations of the AMS measurement approach and reviews how the measurements are used to characterize particle properties. Results from selected lab. expts. and field measurement campaigns are also presented to highlight the different applications of this instrument. Recent instrumental developments, such as the incorporation of softer ionization techniques (vacuum UV (VUV) photo-ionization, Li+ ion, and electron attachment) and high-resoln. ToF mass spectrometers, that yield more detailed information about the org. aerosol component are also described.
    43. 43
      Lopez-Hilfiker, F. D.; Pospisilova, V.; Huang, W.; Kalberer, M.; Mohr, C.; Stefenelli, G.; Thornton, J. A.; Baltensperger, U.; Prevot, A. S. H.; Slowik, J. G. An Extractive Electrospray Ionization Time-of-Flight Mass Spectrometer (EESI-TOF) for Online Measurement of Atmospheric Aerosol Particles. Atmos. Meas. Tech. 2019, 12, 4867– 4886,  DOI: 10.5194/amt-12-4867-2019
      43
      An extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) for online measurement of atmospheric aerosol particles
      Lopez-Hilfiker, Felipe D.; Pospisilova, Veronika; Huang, Wei; Kalberer, Markus; Mohr, Claudia; Stefenelli, Giulia; Thornton, Joel A.; Baltensperger, Urs; Prevot, Andre S. H.; Slowik, Jay G.
      Atmospheric Measurement Techniques (2019), 12 (9), 4867-4886CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
      Real-time, online measurements of atm. org. aerosol (OA) compn. are an essential tool for detg. the emissions sources and physicochem. processes governing aerosol effects on climate and health. Aerosol particles are continuously sampled into the EESI-TOF, where they intersect a spray of charged droplets generated by a conventional electrospray probe. Sol. components are extd. and then ionized as the droplets are evapd. The EESI-TOF achieves a linear response to mass, with detection limits on the order of 1 to 10 ng m-3 in 5 s for typical atmospherically relevant compds. In contrast to conventional electrospray systems, the EESI-TOF response is not significantly affected by a changing OA matrix for the systems investigated. Although the relative sensitivities to a variety of com. available org. stds. vary by more than a factor of 30, the bulk sensitivity to secondary org. aerosol generated from individual precursor gases varies by only a factor of 15. Further, the ratio of compd.-by-compd. sensitivities between the EESI-TOF and an iodide adduct FIGAERO-I-CIMS varies by only ±50%, suggesting that EESI-TOF mass spectra indeed reflect the actual distribution of detectable compds. in the particle phase. Successful deployments of the EESI-TOF for lab. environmental chamber measurements, ground-based ambient sampling, and proof-of-concept measurements aboard a research aircraft highlight the versatility and potential of the EESI-TOF system.
    44. 44
      Wu, C.; Bell, D. M.; Graham, E. L.; Haslett, S.; Riipinen, I.; Baltensperger, U.; Bertrand, A.; Giannoukos, S.; Schoonbaert, J.; El Haddad, I.; Prevot, A. S. H.; Huang, W.; Mohr, C. Photolytically Induced Changes in Composition and Volatility of Biogenic Secondary Organic Aerosol from Nitrate Radical Oxidation during Night-to-Day Transition. Atmos. Chem. Phys. 2021, 21, 14907– 14925,  DOI: 10.5194/acp-21-14907-2021
      44
      Photolytically induced changes in composition and volatility of biogenic secondary organic aerosol from nitrate radical oxidation during night-to-day transition
      Wu, Cheng; Bell, David M.; Graham, Emelie L.; Haslett, Sophie; Riipinen, Ilona; Baltensperger, Urs; Bertrand, Amelie; Giannoukos, Stamatios; Schoonbaert, Janne; El Haddad, Imad; Prevot, Andre S. H.; Huang, Wei; Mohr, Claudia
      Atmospheric Chemistry and Physics (2021), 21 (19), 14907-14925CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Night-time reactions of biogenic volatile org. compds. (BVOCs) and nitrate radicals (NO3) can lead to the formation of NO3-initiated biogenic secondary org. aerosol (BSOANO3). Here, we study the impacts of light exposure on the chem. compn. and volatility of BSOANO3 formed in the dark from three precursors (isoprene, α-pinene, and β-caryophyllene) in atm. simulation chamber expts. Our study represents BSOANO3 formation conditions where reactions between peroxy radicals (RO2 + RO2) and between RO2 and NO3 are favored. The emphasis here is on the identification of particle-phase organonitrates (ONs) formed in the dark and their changes during photolytic ageing on timescales of ~ 1 h. The chem. compn. of particle-phase compds. was measured with a chem. ionization mass spectrometer with a filter inlet for gases and aerosols (FIGAERO-CIMS) and an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF). Volatility information on BSOANO3 was derived from FIGAERO-CIMS desorption profiles (thermograms) and a volatility tandem differential mobility analyzer (VTDMA). During photolytic ageing, there was a relatively small change in mass due to evapn. (< 5% for the isoprene and α-pinene BSOANO3, and 12% for the β-caryophyllene BSOANO3), but we obsd. significant changes in the chem. compn. of the BSOANO3. Overall, 48%, 44%, and 60% of the resp. total signal for the isoprene, α-pinene, and β-caryophyllene BSOANO3 was sensitive to photolytic ageing and exhibited decay. The photolabile compds. include both monomers and oligomers. Oligomers can decomp. into their monomer units through photolysis of the bonds (e.g. likely O-O) between them. Fragmentation of both oligomers and monomers also happened at other positions, causing the formation of compds. with shorter carbon skeletons. The cleavage of the nitrate functional group from the carbon chain was likely not a main degrdn. pathway in our expts. In addn., photolytic degrdn. of compds. changes their volatility and can lead to evapn. We use different methods to assess bulk volatilities and discuss their changes during both dark ageing and photolysis in the context of the chem. changes that we obsd. We also reveal large uncertainties in satn. vapor pressure estd. from parameterizations for the ON oligomers with multiple nitrate groups. Overall, our results suggest that photolysis causes photodegrdn. of a substantial fraction of BSOANO3, changes both the chem. compn. and the bulk volatility of the particles, and might be a potentially important loss pathway of BSOANO3 during the night-to-day transition.
    45. 45
      Wolfe, G. M.; Marvin, M. R.; Roberts, S. J.; Travis, K. R.; Liao, J. The Framework for 0-D Atmospheric Modeling (F0AM) v3.1. Geosci. Model Dev. 2016, 9, 3309– 3319,  DOI: 10.5194/gmd-9-3309-2016
      There is no corresponding record for this reference.
    46. 46
      Saunders, S. M.; Jenkin, M. E.; Derwent, R. G.; Pilling, M. J. Protocol for the Development of the Master Chemical Mechanism, MCM v3 (Part A): Tropospheric Degradation of Non-Aromatic Volatile Organic Compounds. Atmos. Chem. Phys. 2003, 3, 161– 180,  DOI: 10.5194/acp-3-161-2003
      46
      Protocol for the development of the master chemical mechanism, MCM v3 (part A): tropospheric degradation of non-aromatic volatile organic compounds
      Saunders, S. M.; Jenkin, M. E.; Derwent, R. G.; Pilling, M. J.
      Atmospheric Chemistry and Physics (2003), 3 (1), 161-180CODEN: ACPTCE; ISSN:1680-7324. (European Geophysical Society)
      Kinetic and mechanistic data relevant to the tropospheric degrdn. of volatile org. compds. (VOC), and the prodn. of secondary pollutants, were previously used to define a protocol which underpinned the construction of a near-explicit Master Chem. Mechanism. An update to the previous protocol is presented, which was used to define degrdn. schemes for 107 nonarom. VOC as part of version 3 of the Master Chem. Mechanism (MCM v3). The treatment of 18 arom. VOC is described in a companion paper. The protocol is divided into subsections describing initiation reactions, the reactions of the radical intermediates and the further degrdn. of 1st and subsequent generation products. Emphasis is placed on updating the previous information, and outlining the methodol. which is specifically applicable to VOC not considered previously (e.g., α- and β-pinene). The present protocol aims to take into consideration work available in the open literature up to the beginning of 2001, and some other studies known by the authors which were under review at the time. Application of MCM v3 in appropriate box models indicates that the representation of isoprene degrdn. provides a good description of the speciated distribution of oxygenated org. products obsd. in reported field studies where isoprene was the dominant emitted hydrocarbon, and that the α-pinene degrdn. chem. provides a good description of the time dependence of key gas phase species in α-pinene/NOX photooxidn. expts. carried out in the European Photoreactor (EUPHORE). Photochem. Ozone Creation Potentials (POCP) were calcd. for the 106 non-arom. non-methane VOC in MCM v3 for idealized conditions appropriate to north-west Europe, using a photochem. trajectory model. The POCP values provide a measure of the relative ozone forming abilities of the VOC. Where applicable, the values are compared with those calcd. with previous versions of the MCM.
    47. 47
      Jenkin, M. E.; Saunders, S. M.; Pilling, M. J. The Tropospheric Degradation of Volatile Organic Compounds: A Protocol for Mechanism Development. Atmos. Environ. 1997, 31, 81– 104,  DOI: 10.1016/S1352-2310(96)00105-7
      47
      The tropospheric degradation of volatile organic compounds: a protocol for mechanism development
      Jenkin, Michael E.; Saunders, Sandra M.; Pilling, Michael J.
      Atmospheric Environment (1996), 31 (1), 81-104CODEN: AENVEQ; ISSN:1352-2310. (Elsevier)
      Kinetic and mechanistic data relevant to the tropospheric oxidn. of volatile org. compds. (VOCs) were used to define a series of rules for the construction of detailed degrdn. schemes for use in numerical models. These rules are intended to apply to the treatment of a wide range of non-arom. hydrocarbons and oxygenated and chlorinated VOCs, and are currently used to provide an up-to-date mechanism describing the degrdn. of a range of VOCs, and the formation of secondary oxidants, for use in a model of the boundary layer over Europe. The schemes constructed using this protocol are applicable, however, to a wide range of ambient conditions, and may be employed in models of urban, rural, or remote tropospheric environments, or for the simulation of secondary pollutant formation for a range of NOx or VOC emission scenarios. These schemes are believed to be particularly appropriate for comparative assessments of the formation of oxidants, such as ozone, from the degrdn. of org. compds. The protocol is divided into a series of subsections dealing with initiation reactions, the reactions of the radical intermediates and the further degrdn. of first and subsequent generation products. The present work draws heavily on previous reviews and evaluations of data relevant to tropospheric chem. Where necessary, however, existing recommendations are adapted, or new rules are defined, to reflect recent improvements in the database, particularly with regard to the treatment of peroxy radical (RO2) reactions for which there have been major advances, even since comparatively recent reviews. The present protocol aims to take into consideration work available in the open literature up to the end of 1994, and some further studies known by the authors, which were under review at that time. A major disadvantage of explicit chem. mechanisms is the very large no. of reactions potentially generated, if a series of rules is rigorously applied. The protocol aims to limit the no. of reactions in a degrdn. scheme by applying a degree of strategic simplication, while maintaining the essential features of the chem. These simplication measures are described, and their influence is demonstrated and discussed. The resultant mechanisms are believed to provide a suitable starting point for the generation of reduced chem. mechanisms.
    48. 48
      Mellouki, A.; Ammann, M.; Cox, R. A.; Crowley, J. N.; Herrmann, H.; Jenkin, M. E.; Mcneill, V. F.; Troe, J.; Wallington, T. J. Evaluated Kinetic and Photochemical Photochemical Data for Atmospheric Chemistry: Volume VIII - Gas-Phase Reactions of Organic Species with Four, or More, Carbon Atoms (≥ C4). Atmos. Chem. Phys. 2021, 21, 4797– 4808,  DOI: 10.5194/acp-21-4797-2021
      48
      Evaluated kinetic and photochemical data for atmospheric chemistry: volume VIII - gas-phase reactions of organic species with four, or more, carbon atoms (≥ C4)
      Mellouki, Abdelwahid; Ammann, Markus; Cox, R. Anthony; Crowley, John N.; Herrmann, Hartmut; Jenkin, Michael E.; McNeill, V. Faye; Troe, Jurgen; Wallington, Timothy J.
      Atmospheric Chemistry and Physics (2021), 21 (6), 4797-4808CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      This article, the eighth in the series, presents kinetic and photochem. data sheets evaluated by the IUPAC Task Group on Atm. Chem. Kinetic Data Evaluation. It covers the gas phase thermal and photochem. reactions of org. species with four, or more, carbon atoms (C4) available on the IUPAC website in 2021, including thermal reactions of closed-shell org. species with HO and NO3 radicals and their photolysis. The present work is a continuation of vol. II, with new reactions and updated data sheets for reactions of HO (77 reactions) and NO3 (36 reactions) with C4 orgs., including alkanes, alkenes, dienes, aroms., oxygenated, org. nitrates and nitro compds. in addn. to photochem. processes for nine species. The article consists of a summary table, contg. the recommended kinetic parameters for the evaluated reactions, and a supplement contg. the data sheets, which provide information upon which recommendations are made.
    49. 49
      Jenkin, M. E.; Valorso, R.; Aumont, B.; Rickard, A. R.; Wallington, T. J. Estimation of Rate Coefficients and Branching Ratios for Gas-Phase Reactions of OH with Aromatic Organic Compounds for Use in Automated Mechanism Construction. Atmos. Chem. Phys. 2018, 18, 9329– 9349,  DOI: 10.5194/acp-18-9329-2018
      49
      Estimation of rate coefficients and branching ratios for gas-phase reactions of OH with aromatic organic compounds for use in automated mechanism construction
      Jenkin, Michael E.; Valorso, Richard; Aumont, Bernard; Rickard, Andrew R.; Wallington, Timothy J.
      Atmospheric Chemistry and Physics (2018), 18 (13), 9329-9349CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Reaction with the hydroxyl (OH) radical is the dominant removal process for volatile org. compds. (VOCs) in the atm. Rate coeffs. for the reactions of OH with VOCs are therefore essential parameters for chem. mechanisms used in chem. transport models, and are required more generally for impact assessments involving estn. of atm. lifetimes or oxidn. rates for VOCs. A structure-activity relationship (SAR) method is presented for the reactions of OH with arom. org. compds., with the reactions of aliph. org. compds. considered in the preceding companion paper. The SAR is optimized using a preferred set of data including reactions of OH with 67 monocyclic arom. hydrocarbons and oxygenated org. compds. In each case, the rate coeff. is defined in terms of a summation of partial rate coeffs. for H abstraction or OH addn. at each relevant site in the given org. compd., so that the attack distribution is defined. The SAR can therefore guide the representation of the OH reactions in the next generation of explicit detailed chem. mechanisms. Rules governing the representation of the reactions of the product radicals under tropospheric conditions are also summarized, specifically the rapid reaction sequences initiated by their reactions with O2.
    50. 50
      Barmet, P.; Dommen, J.; DeCarlo, P. F.; Tritscher, T.; Praplan, A. P.; Platt, S. M.; Prévôt, A. S. H.; Donahue, N. M.; Baltensperger, U. OH clock determination by proton transfer reaction mass spectrometry at an environmental chamber. Atmos. Meas. Tech. 2012, 5, 647– 656,  DOI: 10.5194/amt-5-647-2012
      50
      OH clock determination by proton transfer reaction mass spectrometry at an environmental chamber
      Barmet, P.; Dommen, J.; DeCarlo, P. F.; Tritscher, T.; Praplan, A. P.; Platt, S. M.; Prevot, A. S. H.; Donahue, N. M.; Baltensperger, U.
      Atmospheric Measurement Techniques (2012), 5 (3), 647-656CODEN: AMTTC2; ISSN:1867-1381. (Copernicus Publications)
      The hydroxyl free radical (OH) is the major oxidizing species in the lower atm. Measuring the OH concn. is generally difficult and involves elaborate, expensive, custom-made exptl. setups. Thus other more economical techniques, capable of detg. OH concns. at environmental chambers, would be valuable. This work is based on an indirect method of OH concn. measurement, by monitoring an appropriate OH tracer by proton transfer reaction mass spectrometry (PTR-MS). 3-Pentanol, 3-pentanone and pinonaldehyde (PA) were used as OH tracers in α-pinene (AP) secondary org. aerosol (SOA) aging studies. In addn. we tested butanol-d9 as a potential "universal" OH tracer and detd. its reaction rate const. with OH: kbutanol-d9 = 3-4(±0.88) × 10-12 cm3 mol.-1 s-1. In order to make the chamber studies more comparable among each other as well as to atm. measurements we suggest the use of a chem. (time) dimension: the OH clock, which corresponds to the integrated OH concn. over time.
    51. 51
      Thomsen, D.; Thomsen, L. D.; Iversen, E. M.; Björgvinsdóttir, T. N.; Vinther, S. F.; Skønager, J. T.; Hoffmann, T.; Elm, J.; Bilde, M.; Glasius, M. Ozonolysis of α-Pinene and Δ3-Carene Mixtures: Formation of Dimers with Two Precursors. Environ. Sci. Technol. 2022, 56, 16643– 16651,  DOI: 10.1021/acs.est.2c04786
      51
      Ozonolysis of α-Pinene and Δ3-Carene Mixtures: Formation of Dimers with Two Precursors
      Thomsen, Ditte; Thomsen, Lotte Dyrholm; Iversen, Emil Mark; Bjorgvinsdottir, Thuridjur Nott; Vinther, Sofie Falk; Skoenager, Jane Tygesen; Hoffmann, Thorsten; Elm, Jonas; Bilde, Merete; Glasius, Marianne
      Environmental Science & Technology (2022), 56 (23), 16643-16651CODEN: ESTHAG; ISSN:1520-5851. (American Chemical Society)
      The formation of secondary org. aerosol (SOA) from the structurally similar monoterpenes, α-pinene and Δ3-carene, differs substantially. The aerosol phase is already complex for a single precursor, and when mixts. are oxidized, products, e.g., dimers, may form between different volatile org. compds. (VOCs). This work investigates whether differences in SOA formation and properties from the oxidn. of individual monoterpenes persist when a mixt. of the monoterpenes is oxidized. Ozonolysis of α-pinene, Δ3-carene, and a 1:1 mixt. of them was performed in the Aarhus University Research on Aerosol (AURA) atm. simulation chamber. Here, ~ 100 ppb of monoterpene was oxidized by 200 ppb O3 under dark conditions at 20°C. The particle no. concn. and particle mass concn. for ozonolysis of α-pinene exceed those from ozonolysis of Δ3-carene alone, while their mixt. results in concns. similar to α-pinene ozonolysis. Detailed offline anal. reveals evidence of VOC-cross-product dimers in SOA from ozonolysis of the monoterpene mixt.: a VOC-cross-product dimer likely composed of the monomeric units cis-caric acid and 10-hydroxy-pinonic acid and a VOC-cross-product dimer ester likely from the monomeric units caronaldehyde and terpenylic acid were tentatively identified by liq. chromatog.-mass spectrometry. To improve the understanding of chem. mechanisms detg. SOA, it is relevant to identify VOC-cross-products.
    52. 52
      Bell, D. M.; Pospisilova, V.; Lopez-Hilfiker, F.; Bertrand, A.; Xiao, M.; Zhou, X.; Huang, W.; Wang, D. S.; Lee, C. P.; Dommen, J.; Baltensperger, U.; Prevot, A. S. H.; El Haddad, I.; Slowik, J. G. Effect of OH scavengers on the chemical composition of α-pinene secondary organic aerosol. Environ. Sci.: Atmos. 2023, 3, 115– 123,  DOI: 10.1039/D2EA00105E
      52
      Effect of OH scavengers on the chemical composition of α-pinene secondary organic aerosol
      Bell, David M.; Pospisilova, Veronika; Lopez-Hilfiker, Felipe; Bertrand, Amelie; Xiao, Mao; Zhou, Xueqin; Huang, Wei; Wang, Dongyu S.; Lee, Chuan Ping; Dommen, Josef; Baltensperger, Urs; Prevot, Andre S. H.; El Haddad, Imad; Slowik, Jay G.
      Environmental Science: Atmospheres (2023), 3 (1), 115-123CODEN: ESANC9; ISSN:2634-3606. (Royal Society of Chemistry)
      OH scavengers are extensively used in studies of secondary org. aerosol (SOA) because they create an idealized environment where only a single oxidn. pathway is occurring. Here, we present a detailed mol. characterization of SOA produced from α-pinene + O3 with a variety of OH scavengers using the extractive electrospray time-of-flight mass spectrometer in our atm. simulation chamber, which is complemented by characterizing the gas phase compn. in flow reactor expts. Under our exptl. conditions, radical chem. largely controls the compn. of SOA. Besides playing their desired role in suppressing the reaction of α-pinene with OH, OH scavengers alter the reaction pathways of radicals produced from α-pinene + O3. This involves changing the HO2 : RO2 ratio, the identity of the RO2 radicals present, and the RO2 major sinks. As a result, the use of the OH scavengers has significant effects on the compn. of SOA, including inclusions of scavenger mols. in SOA, the promotion of fragmentation reactions, and depletion of dimers formed via α-pinene RO2-RO2 reactions. To date fragmentation reactions and inclusion of OH scavenger products into secondary org. aerosol have not been reported in atm. simulation chamber studies. Therefore, care should be considered if and when to use an OH scavenger during expts.
    53. 53
      Berndt, T.; Richters, S.; Jokinen, T.; Hyttinen, N.; Kurtén, T.; Otkjær, R. V.; Kjaergaard, H. G.; Stratmann, F.; Herrmann, H.; Sipilä, M.; Kulmala, M.; Ehn, M. Hydroxyl Radical-Induced Formation of Highly Oxidized Organic Compounds. Nat. Commun. 2016, 7, 13677,  DOI: 10.1038/ncomms13677
      53
      Hydroxyl radical-induced formation of highly oxidized organic compounds
      Berndt, Torsten; Richters, Stefanie; Jokinen, Tuija; Hyttinen, Noora; Kurten, Theo; Otkjaer, Rasmus V.; Kjaergaard, Henrik G.; Stratmann, Frank; Herrmann, Hartmut; Sipilae, Mikko; Kulmala, Markku; Ehn, Mikael
      Nature Communications (2016), 7 (), 13677CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
      Explaining the formation of secondary org. aerosol is an intriguing question in atm. sciences because of its importance for Earth's radiation budget and the assocd. effects on health and ecosystems. A breakthrough was recently achieved in the understanding of secondary org. aerosol formation from ozone reactions of biogenic emissions by the rapid formation of highly oxidized multifunctional org. compds. via autoxidn. However, the important daytime hydroxyl radical reactions have been considered to be less important in this process. Here we report measurements on the reaction of hydroxyl radicals with α- and β-pinene applying improved mass spectrometric methods. Our lab. results prove that the formation of highly oxidized products from hydroxyl radical reactions proceeds with considerably higher yields than previously reported. Field measurements support these findings. Our results allow for a better description of the diurnal behavior of the highly oxidized product formation and subsequent secondary org. aerosol formation in the atm.
    54. 54
      Ehn, M.; Thornton, J. A.; Kleist, E.; Sipilä, M.; Junninen, H.; Pullinen, I.; Springer, M.; Rubach, F.; Tillmann, R.; Lee, B.; Lopez-Hilfiker, F.; Andres, S.; Acir, I.-H.; Rissanen, M.; Jokinen, T.; Schobesberger, S.; Kangasluoma, J.; Kontkanen, J.; Nieminen, T.; Kurtén, T.; Nielsen, L. B.; Jørgensen, S.; Kjaergaard, H. G.; Canagaratna, M.; Maso, M. D.; Berndt, T.; Petäjä, T.; Wahner, A.; Kerminen, V.-M.; Kulmala, M.; Worsnop, D. R.; Wildt, J.; Mentel, T. F. A Large Source of Low-Volatility Secondary Organic Aerosol. Nature 2014, 506, 476– 479,  DOI: 10.1038/nature13032
      54
      A large source of low-volatility secondary organic aerosol
      Ehn, Mikael; Thornton, Joel A.; Kleist, Einhard; Sipilae, Mikko; Junninen, Heikki; Pullinen, Iida; Springer, Monika; Rubach, Florian; Tillmann, Ralf; Lee, Ben; Lopez-Hilfiker, Felipe; Andres, Stefanie; Acir, Ismail-Hakki; Rissanen, Matti; Jokinen, Tuija; Schobesberger, Siegfried; Kangasluoma, Juha; Kontkanen, Jenni; Nieminen, Tuomo; Kurten, Theo; Nielsen, Lasse B.; Jorgensen, Solvejg; Kjaergaard, Henrik G.; Canagaratna, Manjula; Dal Maso, Miikka; Berndt, Torsten; Petaejae, Tuukka; Wahner, Andreas; Kerminen, Veli-Matti; Kulmala, Markku; Worsnop, Douglas R.; Wildt, Juergen; Mentel, Thomas F.
      Nature (London, United Kingdom) (2014), 506 (7489), 476-479CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
      Forests emit large quantities of volatile org. compds. (VOC) to the atm. Their condensable oxidn. products can form secondary org. aerosols (SOA), a significant, ubiquitous component of atm. aerosol known to affect the Earth radiation balance by scattering solar radiation and acting as cloud condensation nuclei. A quant. assessment of such climate effects is hampered by several factors, including an incomplete understanding of how biogenic VOC contribute to formation of atm. SOA. Growth of newly formed particle sizes from <3 nm to cloud condensation nuclei (∼100 nm) in many continental ecosystems requires abundant, essentially non-volatile org. vapor, but sources and compns. of such vapors are unknown. This work examd. oxidn. of VOC, particularly the terpene, α-pinene, under atmospherically relevant conditions in chamber expts. A direct pathway leads from several biogenic VOC, e.g., monoterpenes, to formation of large amts. of extremely low-volatility vapors. These vapors form at significant mass yields in the gas phase and condense irreversibly onto aerosol surfaces producing SOA, helping to explain the discrepancy between the obsd. atm. burden of SOA and that reported in many model studies. Results further demonstrated how these low-volatility vapors can enhance or even dominate, aerosol formation and growth over forested regions, providing a missing link between biogenic VOC and their conversion to aerosol particles. Results could help improve biosphere-aerosol-climate feedback mechanism assessments, and biogenic emissions/air quality and climate effects generally.
    55. 55
      Kristensen, K.; Watne, Å. K.; Hammes, J.; Lutz, A.; Petäjä, T.; Hallquist, M.; Bilde, M.; Glasius, M. High-Molecular Weight Dimer Esters Are Major Products in Aerosols from α-Pinene Ozonolysis and the Boreal Forest. Environ. Sci. Technol. Lett. 2016, 3, 280– 285,  DOI: 10.1021/acs.estlett.6b00152
      55
      High-Molecular Weight Dimer Esters Are Major Products in Aerosols from α-Pinene Ozonolysis and the Boreal Forest
      Kristensen, Kasper; Watne, Aagot K.; Hammes, Julia; Lutz, Anna; Petaja, Tuukka; Hallquist, Mattias; Bilde, Merete; Glasius, Marianne
      Environmental Science & Technology Letters (2016), 3 (8), 280-285CODEN: ESTLCU; ISSN:2328-8930. (American Chemical Society)
      This study studies the contribution of high-mol. wt. dimer esters to lab.-generated α-pinene gas- and particle-phase secondary org. aerosol (SOA) and particulate matter (PM) collected at the Nordic boreal forest site in Finland. Lab. flow reactor expts. (25°) show that dimer esters from ozonolysis of α-pinene contribute between 5 and 16% of the freshly formed α-pinene particle-phase SOA mass. An increased level of formation is obsd. at a higher relative humidity of ∼40%, and the presence of a hydroxyl radical (OH) scavenger is shown to affect the formation of dimer esters. Of the 28 dimer esters identified in lab. α-pinene SOA, 15 are also obsd. in ambient PM samples, contributing between 0.5 and 1.6% of the total PM1. The obsd. esters show good correlation with known α-pinene SOA tracers in collected PM samples. This work reveals an, until now, unrecognized contribution of dimer esters from α-pinene oxidn. to boreal forest PM.
    56. 56
      Zhang, X.; McVay, R. C.; Huang, D. D.; Dalleska, N. F.; Aumont, B.; Flagan, R. C.; Seinfeld, J. H. Formation and evolution of molecular products in α-pinene secondary organic aerosol. Proc. Natl. Acad. Sci. U.S.A. 2015, 112, 14168– 14173,  DOI: 10.1073/pnas.1517742112
      56
      Formation and evolution of molecular products in α-pinene secondary organic aerosol
      Zhang, Xuan; McVay, Renee C.; Huang, Dan D.; Dalleska, Nathan F.; Aumont, Bernard; Flagan, Richard C.; Seinfeld, John H.
      Proceedings of the National Academy of Sciences of the United States of America (2015), 112 (46), 14168-14173CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
      Much of the understanding of atm. secondary org. aerosol (SOA) formation from volatile org. compds. is from lab. chamber measurements, including mass yield and elemental compn. These measurements alone are insufficient to identify chem. mechanisms for SOA prodn. A comprehensive dataset on the mol. identity, abundance, and kinetics of α-pinene SOA, a canonical system which received much attention due to its importance as an org. aerosol source in the pristine atm., is presented. Identified org. species accounted for ∼58-72% of the α-pinene SOA mass and were characterized as semi-volatile/low-volatility monomers and extremely low volatility dimers, which exhibited comparable oxidn. states yet different functionalities. For the first time, the α-pinene SOA formation process features are revealed from the dynamics of individual particle-phase components. Although monomeric products dominate the overall aerosol mass, rapid prodn. of dimers plays a key role in initiating particle growth. Continuous monomer prodn. is obsd. after the parent (α-pinene) is consumed, which cannot be explained solely by gas-phase photochem. prodn. Also, distinct monomer and dimer responses to α-pinene oxidn. by O3 vs. OH-, temp., and relative humidity were obsd. Gas-phase radical combination reactions in conjunction with labile mol. condensed phase rearrangement potentially explain the newly characterized SOA features and open up further avenues to understand α-pinene SOA formation and evolution mechanisms.
    57. 57
      Wang, D. S.; Lee, C. P.; Krechmer, J. E.; Majluf, F.; Tong, Y.; Canagaratna, M. R.; Schmale, J.; Prévôt, A. S. H.; Baltensperger, U.; Dommen, J.; El Haddad, I.; Slowik, J. G.; Bell, D. M. Constraining the Response Factors of an Extractive Electrospray Ionization Mass Spectrometer for Near-Molecular Aerosol Speciation. Atmos. Meas. Tech. 2021, 14, 6955– 6972,  DOI: 10.5194/amt-14-6955-2021
      57
      Constraining the response factors of an extractive electrospray ionization mass spectrometer for near-molecular aerosol speciation
      Wang, Dongyu S.; Lee, Chuan Ping; Krechmer, Jordan E.; Majluf, Francesca; Tong, Yandong; Canagaratna, Manjula R.; Schmale, Julia; Prevot, Andre S. H.; Baltensperger, Urs; Dommen, Josef; El Haddad, Imad; Slowik, Jay G.; Bell, David M.
      Atmospheric Measurement Techniques (2021), 14 (11), 6955-6972CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
      Online characterization of aerosol compn. at the near-mol. level is key to understanding chem. reaction mechanisms, kinetics, and sources under various atm. conditions. The recently developed extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) is capable of detecting a wide range of org. oxidn. products in the particle phase in real time with minimal fragmentation. Quantification can sometimes be hindered by a lack of available com. stds. for aerosol constituents, however. Good correlations between the EESI-TOF and other aerosol speciation techniques have been reported, though no attempts have yet been made to parameterize the EESI-TOF response factor for different chem. species. Here, we report the first parameterization of the EESI-TOF response factor for secondary org. aerosol (SOA) at the near-mol. level based on its elemental compn. SOA was formed by ozonolysis of monoterpene or OH oxidn. of aroms. inside an oxidn. flow reactor (OFR) using ammonium nitrate as seed particles. A Vocus proton-transfer reaction mass spectrometer (Vocus-PTR) and a high-resoln. aerosol mass spectrometer (AMS) were used to det. the gas-phase mol. compn. and the particle-phase bulk chem. compn., resp. The EESI response factors towards bulk SOA coating and the inorg. seed particle core were constrained by intercomparison with the AMS. The highest bulk EESI response factor was obsd. for SOA produced from 1,3,5-trimethylbenzene, followed by those produced from d-limonene and o-cresol, consistent with previous findings. The near-mol. EESI response factors were derived from intercomparisons with VocusPTR measurements and were found to vary from 103 to 106 ion counts s-1 ppb-1, mostly within ±1 order of magnitude of their geometric mean of 104.6 ion counts s-1 ppb-1. For arom. SOA components, the EESI response factors correlated with mol. wt. and oxygen content and inversely correlated with volatility. The near-mol. response factors mostly agreed within a factor of 20 for isomers obsd. across the aroms. and biogenic systems. Parameterization of the near-mol. response factors based on the measured elemental formulas could reproduce the empirically detd. response factor for a single volatile org. compd. (VOC) system to within a factor of 5 for the configuration of our mass spectrometers. The results demonstrate that std.-free quantification using the EESI-TOF is possible.
    58. 58
      Canagaratna, M. R.; Jimenez, J. L.; Kroll, J. H.; Chen, Q.; Kessler, S. H.; Massoli, P.; Hildebrandt Ruiz, L.; Fortner, E.; Williams, L. R.; Wilson, K. R.; Surratt, J. D.; Donahue, N. M.; Jayne, J. T.; Worsnop, D. R. Elemental Ratio Measurements of Organic Compounds Using Aerosol Mass Spectrometry: Characterization, Improved Calibration, and Implications. Atmos. Chem. Phys. 2015, 15, 253– 272,  DOI: 10.5194/acp-15-253-2015
      58
      Elemental ratio measurements of organic compounds using aerosol mass spectrometry: characterization, improved calibration, and implications
      Canagaratna, M. R.; Jimenez, J. L.; Kroll, J. H.; Chen, Q.; Kessler, S. H.; Massoli, P.; Hildebrandt Ruiz, L.; Fortner, E.; Williams, L. R.; Wilson, K. R.; Surratt, J. D.; Donahue, N. M.; Jayne, J. T.; Worsnop, D. R.
      Atmospheric Chemistry and Physics (2015), 15 (1), 253-272/1-253-272/20, 20 pp.CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Elemental compns. of org. aerosol (OA) particles provide useful constraints on OA sources, chem. evolution, and effects. The Aerodyne high-resoln. time-of-flight aerosol mass spectrometer (HR-ToF-AMS) is widely used to measure OA elemental compn. This study evaluates AMS measurements of at. oxygen-to-carbon (O : C), hydrogen-to-carbon (H : C), and org. mass-to-org. carbon (OM : OC) ratios, and of carbon oxidn. state ‾(O‾ SC) for a vastly expanded lab. data set of multifunctional oxidized OA stds. For the expanded std. data set, the method introduced by Aiken et al. (2008), which uses exptl. measured ion intensities at all ions to det. elemental ratios (referred to here as "Aiken-Explicit"), reproduces known O : C and H : C ratio values within 20% (av. abs. value of relative errors) and 12%, resp. The more commonly used method, which uses empirically estd. H2O+ and CO+ ion intensities to avoid gas phase air interferences at these ions (referred to here as "Aiken-Ambient"), reproduces O : C and H : C of multifunctional oxidized species within 28 and 14% of known values. The values from the latter method are systematically biased low, however, with larger biases obsd. for alcs. and simple diacids. A detailed examn. of the H2O+, CO+, and CO2+ fragments in the high-resoln. mass spectra of the std. compds. indicates that the Aiken-Ambient method underestimates the CO+ and esp. H2O+ produced from many oxidized species. Combined AMS-vacuum UV (VUV) ionization measurements indicate that these ions are produced by dehydration and decarboxylation on the AMS vaporizer (usually operated at 600 °C). Thermal decompn. is obsd. to be efficient at vaporizer temps. down to 200 °C. These results are used together to develop an "Improved-Ambient" elemental anal. method for AMS spectra measured in air. The Improved-Ambient method uses specific ion fragments as markers to correct for mol. functionality-dependent systematic biases and reproduces known O : C (H : C) ratios of individual oxidized stds. within 28% (13%) of the known mol. values. The error in Improved-Ambient O : C (H : C) values is smaller for theor. std. mixts. of the oxidized org. stds., which are more representative of the complex mix of species present in ambient OA. For ambient OA, the Improved-Ambient method produces O : C (H : C) values that are 27% (11%) larger than previously published Aiken-Ambient values; a corresponding increase of 9% is obsd. for OM : OC values. These results imply that ambient OA has a higher relative oxygen content than previously estd. The‾ ‾OSC values calcd. for ambient OA by the two methods agree well, however (av. relative difference of 0.06‾ ‾OSC units). This indicates that‾ ‾OSC is a more robust metric of oxidn. than O : C, likely since‾ ‾OSC is not affected by hydration or dehydration, either in the atm. or during anal.
    59. 59
      Aiken, A. C.; DeCarlo, P. F.; Jimenez, J. L. Elemental Analysis of Organic Species with Electron Ionization High-Resolution Mass Spectrometry. Anal. Chem. 2007, 79, 8350– 8358,  DOI: 10.1021/ac071150w
      59
      Elemental analysis of organic species with electron ionization high-resolution mass spectrometry
      Aiken, Allison C.; DeCarlo, Peter F.; Jimenez, Jose L.
      Analytical Chemistry (Washington, DC, United States) (2007), 79 (21), 8350-8358CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
      The authors present a new elemental anal. (EA) technique for org. species (CHNO) that allows fast online anal. (10 s) and reduces the required sample size to ∼1 ng, ∼6 orders of magnitude less than std. techniques. The compn. of the analyzed samples is approximated by the av. elemental compn. of the ions from high-resoln. electron ionization (EI) mass spectra. EA of org. species can be performed on org./inorg. mixts. Elemental ratios for the total org. mass, such as oxygen/carbon (O/C), hydrogen/carbon (H/C), and nitrogen/carbon (N/C), in addn. to the org. mass to org. carbon ratio (OM/OC), can be detd. As deviations between the mol. and the ionic compn. can appear due to chem. influences on the ion fragmentation processes, the method was evaluated and calibrated using spectra from 20 compds. from the NIST database and from 35 lab. stds. sampled with the high-resoln. time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The anal. of AMS (NIST) spectra indicates that quantification of O/C is possible with an error (av. abs. value of the relative error) of 30% (17%) for individual species. Precision is much better than accuracy at ±5% in the absence of air for AMS data. AMS OM/OC has an av. error of 5%. Addnl. calibration is recommended for types of species very different from those analyzed here. EA was applied to org. mixts. and ambient aerosols (sampled at 20 s from aircraft). The technique is also applicable to other EI-HRMS measurements such as direct injection MS.
    60. 60
      Stefenelli, G.; Pospisilova, V.; Lopez-Hilfiker, F. D.; Daellenbach, K. R.; Hüglin, C.; Tong, Y.; Baltensperger, U.; Prévôt, A. S. H.; Slowik, J. G. Organic Aerosol Source Apportionment in Zurich Using an Extractive Electrospray Ionization Time-of-Flight Mass Spectrometer (EESI-TOF-MS) -- Part 1: Biogenic Influences and Day-Night Chemistry in Summer. Atmos. Chem. Phys. 2019, 19, 14825– 14848,  DOI: 10.5194/acp-19-14825-2019
      60
      Organic aerosol source apportionment in Zurich using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) - part 1: biogenic influences and day-night chemistry in summer
      Stefenelli, Giulia; Pospisilova, Veronika; Lopez-Hilfiker, Felipe D.; Daellenbach, Kaspar R.; Huglin, Christoph; Tong, Yandong; Baltensperger, Urs; Prevot, Andre S. H.; Slowik, Jay G.
      Atmospheric Chemistry and Physics (2019), 19 (23), 14825-14848CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Improving the understanding of the health and climate impacts of aerosols remains challenging and is restricted by the limitations of current measurement techniques. Detailed investigation of secondary org. aerosol (SOA), which is typically the dominating fraction of the org. aerosol (OA), requires instrumentation capable of real-time, in situ measurements of mol. compn. In this study, we present the first ambient measurements by a novel extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS). The EESI-TOF-MS was deployed along with a high-resoln. time-of-flight aerosol mass spectrometer (HR-ToF-AMS) during summer 2016 at an urban location (Zurich, Switzerland). Pos. matrix factorization (PMF), implemented within the Multilinear Engine (ME-2), was applied to the data from both instruments to quantify the primary and secondary contributions to OA. From the EESI-TOF-MS anal., a six-factor soln. was selected as the most representative and interpretable soln. for the investigated dataset, including two primary and four secondary factors. The primary factors are dominated by cooking and cigarette smoke signatures while the secondary factors are discriminated according to their daytime (two factors) and night-time (two factors) chem. All four factors showed strong influence by biogenic emissions but exhibited significant day-night differences.
    61. 61
      Tiitta, P.; Leskinen, A.; Hao, L.; Yli-Pirilä, P.; Kortelainen, M.; Grigonyte, J.; Tissari, J.; Lamberg, H.; Hartikainen, A.; Kuuspalo, K.; Kortelainen, A.-M.; Virtanen, A.; Lehtinen, K. E. J.; Komppula, M.; Pieber, S.; Prévôt, A. S. H.; Onasch, T. B.; Worsnop, D. R.; Czech, H.; Zimmermann, R.; Jokiniemi, J.; Sippula, O. Transformation of Logwood Combustion Emissions in a Smog Chamber: Formation of Secondary Organic Aerosol and Changes in the Primary Organic Aerosol upon Daytime and Nighttime Aging. Atmos. Chem. Phys. 2016, 16, 13251– 13269,  DOI: 10.5194/acp-16-13251-2016
      61
      Transformation of logwood combustion emissions in a smog chamber: formation of secondary organic aerosol and changes in the primary organic aerosol upon daytime and nighttime aging
      Tiitta, Petri; Leskinen, Ari; Hao, Liqing; Yli-Pirila, Pasi; Kortelainen, Miika; Grigonyte, Julija; Tissari, Jarkko; Lamberg, Heikki; Hartikainen, Anni; Kuuspalo, Kari; Kortelainen, Aki-Matti; Virtanen, Annele; Lehtinen, Kari E. J.; Komppula, Mika; Pieber, Simone; Prevot, Andre S. H.; Onasch, Timothy B.; Worsnop, Douglas R.; Czech, Hendryk; Zimmermann, Ralf; Jokiniemi, Jorma; Sippula, Olli
      Atmospheric Chemistry and Physics (2016), 16 (20), 13251-13269CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Org. aerosols (OA) derived from small-scale wood combustion emissions are not well represented by current emissions inventories and models, although they contribute substantially to the atm. particulate matter (PM) levels. In this work, a 29 m3 smog chamber in the ILMARI facility of the University of Eastern Finland was utilized to investigate the formation of secondary org. aerosol (SOA) from a small-scale modern masonry heater commonly used in northern Europe. Emissions were oxidatively aged in the smog chamber for a variety of dark (i.e., O3 and NO3) and UV (i.e., OH) conditions, with OH concn. levels of (0.5-5) × 106 mols. cm-3, achieving equiv. atm. aging of up to 18 h. An aerosol mass spectrometer characterized the direct OA emissions and the SOA formed from the combustion of three wood species (birch, beech and spruce) using two ignition processes (fast ignition with a VOC-to-NOx ratio of 3 and slow ignition with a ratio of 5). Dark and UV aging increased the SOA mass fraction with av. SOA productions 2.0 times the initial OA mass loadings. SOA enhancement was found to be higher for the slow ignition compared with fast ignition conditions. Pos. matrix factorization (PMF) was used to sep. SOA, primary org. aerosol (POA) and their subgroups from the total OA mass spectra. PMF anal. identified two POA and three SOA factors that correlated with the three major oxidizers: ozone, the nitrate radical and the OH radical. Organonitrates (ONs) were obsd. to be emitted directly from the wood combustion and addnl. formed during oxidn. via NO3 radicals (dark aging), suggesting small-scale wood combustion may be a significant ON source. POA was oxidized after the ozone addn., forming aged POA, and after 7 h of aging more than 75 % of the original POA was transformed. This process may involve evapn. and homogeneous gas-phase oxidn. as well as heterogeneous oxidn. of particulate org. matter. The results generally prove that logwood burning emissions are the subject of intensive chem. processing in the atm., and the timescale for these transformations is relatively short, i.e., hours.
    62. 62
      Chhabra, P. S.; Flagan, R. C.; Seinfeld, J. H. Elemental Analysis of Chamber Organic Aerosol Using an Aerodyne High-Resolution Aerosol Mass Spectrometer. Atmos. Chem. Phys. 2010, 10, 4111– 4131,  DOI: 10.5194/acp-10-4111-2010
      62
      Elemental analysis of chamber organic aerosol using an aerodyne high-resolution aerosol mass spectrometer
      Chhabra, P. S.; Flagan, R. C.; Seinfeld, J. H.
      Atmospheric Chemistry and Physics (2010), 10 (9), 4111-4131CODEN: ACPTCE; ISSN:1680-7316. (Copernicus Publications)
      The elemental compn. of lab. chamber secondary org. aerosol (SOA) from glyoxal uptake, α-pinene ozonolysis, isoprene photooxidn., single-ring arom. photooxidn., and naphthalene photooxidn. is evaluated using Aerodyne high-resoln. time-of-flight mass spectrometer data. SOA O/C ratios range from 1.13 for glyoxal uptake expts. to 0.30-0.43 for α-pinene ozonolysis. The elemental compn. of α-pinene and naphthalene SOA is also confirmed by offline mass spectrometry. The fraction of org. signal at m/z 44 is generally a good measure of SOA oxygenation for α-pinene/O3, isoprene/high-NOx, and naphthalene SOA systems. The agreement between measured and estd. O/C ratios tends to get closer as the fraction of org. signal at m/z 44 increases. This is in contrast to the glyoxal uptake system, in which m/z 44 substantially underpredicts O/C. Although chamber SOA has generally been considered less oxygenated than ambient SOA, single-ring arom.- and naphthalene-derived SOA can reach O/C ratios upward of 0.7, well within the range of ambient PMF component OOA, though still not as high as some ambient measurements. The spectra of arom. and isoprene-high-NOx SOA resemble that of OOA, but the spectrum of glyoxal uptake does not resemble that of any ambient org. aerosol PMF component.
    63. 63
      Garmash, O.; Rissanen, M. P.; Pullinen, I.; Schmitt, S.; Kausiala, O.; Tillmann, R.; Zhao, D.; Percival, C.; Bannan, T. J.; Priestley, M.; Hallquist, Å. M.; Kleist, E.; Kiendler-Scharr, A.; Hallquist, M.; Berndt, T.; McFiggans, G.; Wildt, J.; Mentel, T. F.; Ehn, M. Multi-Generation OH Oxidation as a Source for Highly Oxygenated Organic Molecules from Aromatics. Atmos. Chem. Phys. 2020, 20, 515– 537,  DOI: 10.5194/acp-20-515-2020
      63
      Multi-generation hydroxyl radicals oxidation as a source for highly oxygenated organic molecules from aromatics
      Garmash, Olga; Rissanen, Matti P.; Pullinen, Iida; Schmitt, Sebastian; Kausiala, Oskari; Tillmann, Ralf; Zhao, Defeng; Percival, Carl; Bannan, Thomas J.; Priestley, Michael; Hallquist, Asa M.; Kleist, Einhard; Kiendler-Scharr, Astrid; Hallquist, Mattias; Berndt, Torsten; McFiggans, Gordon; Wildt, Jurgen; Mentel, Thomas F.; Ehn, Mikael
      Atmospheric Chemistry and Physics (2020), 20 (1), 515-537CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Recent studies have recognized highly oxygenated org. mols. (HOMs) in the atm. as important in the formation of secondary org. aerosol (SOA). A large no. of studies have focused on HOM formation from oxidn. of biogenically emitted monoterpenes. However, HOM formation from anthropogenic vapors has so far received much less attention. Previous studies have identified the importance of arom. volatile org. compds. (VOCs) for SOA formation. In this study, we investigated several arom. compds., benzene (C6H6), toluene (C7H8), and naphthalene (C10H8), for their potential to form HOMs upon reaction with hydroxyl radicals (OH). We performed flow tube expts. with all three VOCs and focused in detail on benzene HOM formation in the Julich Plant Atm. Chamber (JPAC). In JPAC, we also investigated the response of HOMs to NOx and seed aerosol. Using a nitrate-based chem. ionisation mass spectrometer (CI-APi-TOF), we obsd. the formation of HOMs in the flow reactor oxidn. of benzene from the first OH attack. However, in the oxidn. of toluene and naphthalene, which were injected at lower concns., multigeneration OH oxidn. seemed to impact the HOM compn. We tested this in more detail for the benzene system in the JPAC, which allowed for studying longer residence times. The results showed that the apparent molar benzene HOM yield under our exptl. conditions varied from 4.1% to 14.0%, with a strong dependence on the OH concn., indicating that the majority of obsd. HOMs formed through multiple OH-oxidn. steps. The compn. of the identified HOMs in the mass spectrum also supported this hypothesis. By injecting only phenol into the chamber, we found that phenol oxidn. cannot be solely responsible for the obsd. HOMs in benzene expts. When NOx was added to the chamber, HOM compn. changed and many oxygenated nitrogen-contg. products were obsd. in CI-APi-TOF. Upon seed aerosol injection, the HOM loss rate was higher than predicted by irreversible condensation, suggesting that some undetected oxygenated intermediates also condensed onto seed aerosol, which is in line with the hypothesis that some of the HOMs were formed in multi-generation OH oxidn. Based on our results, we conclude that HOM yield and compn. in arom. systems strongly depend on OH and VOC concn. and more studies are needed to fully understand this effect on the formation of HOMs and, consequently, SOA. We also suggest that the dependence of HOM yield on chamber conditions may explain part of the variability in SOA yields reported in the literature and strongly advise monitoring HOMs in future SOA studies.
    64. 64
      Kiendler-Scharr, A.; Mensah, A. A.; Friese, E.; Topping, D.; Nemitz, E.; Prevot, A. S. H.; Äijälä, M.; Allan, J.; Canonaco, F.; Canagaratna, M.; Carbone, S.; Crippa, M.; Dall Osto, M.; Day, D. A.; De Carlo, P.; Di Marco, C. F.; Elbern, H.; Eriksson, A.; Freney, E.; Hao, L.; Herrmann, H.; Hildebrandt, L.; Hillamo, R.; Jimenez, J. L.; Laaksonen, A.; McFiggans, G.; Mohr, C.; O’Dowd, C.; Otjes, R.; Ovadnevaite, J.; Pandis, S. N.; Poulain, L.; Schlag, P.; Sellegri, K.; Swietlicki, E.; Tiitta, P.; Vermeulen, A.; Wahner, A.; Worsnop, D.; Wu, H.-C. Ubiquity of Organic Nitrates from Nighttime Chemistry in the European Submicron Aerosol. Geophys. Res. Lett. 2016, 43, 7735– 7744,  DOI: 10.1002/2016GL069239
      64
      Ubiquity of organic nitrates from night time chemistry in the European submicron aerosol
      Kiendler-Scharr, A.; Mensah, A. A.; Friese, E.; Topping, D.; Nemitz, E.; Prevot, A. S. H.; Aeijaelae, M.; Allan, J.; Canonaco, F.; Canagaratna, M.; Carbone, S.; Crippa, M.; Dall Osto, M.; Day, D. A.; De Carlo, P.; Di Marco, C. F.; Elbern, H.; Eriksson, A.; Freney, E.; Hao, L.; Herrmann, H.; Hildebrandt, L.; Hillamo, R.; Jimenez, J. L.; Laaksonen, A.; McFiggans, G.; Mohr, C.; O'Dowd, C.; Otjes, R.; Ovadnevaite, J.; Pandis, S. N.; Poulain, L.; Schlag, P.; Sellegri, K.; Swietlicki, E.; Tiitta, P.; Vermeulen, A.; Wahner, A.; Worsnop, D.; Wu, H.-C.
      Geophysical Research Letters (2016), 43 (14), 7735-7744CODEN: GPRLAJ; ISSN:1944-8007. (Wiley-Blackwell)
      In the atm. nighttime removal of volatile org. compds. is initiated to a large extent by reaction with the nitrate radical (NO3) forming org. nitrates which partition between gas and particulate phase. Here we show based on particle phase measurements performed at a suburban site in the Netherlands that org. nitrates contribute substantially to particulate nitrate and org. mass. Comparisons with a chem. transport model indicate that most of the measured particulate org. nitrates are formed by NO3 oxidn. Using aerosol compn. data from three intensive observation periods at numerous measurement sites across Europe, we conclude that org. nitrates are a considerable fraction of fine particulate matter (PM1) at the continental scale. Org. nitrates represent 34% to 44% of measured submicron aerosol nitrate and are found at all urban and rural sites, implying a substantial potential of PM redn. by NOx emission control.
    65. 65
      Pye, H. O. T.; Luecken, D. J.; Xu, L.; Boyd, C. M.; Ng, N. L.; Baker, K. R.; Ayres, B. R.; Bash, J. O.; Baumann, K.; Carter, W. P. L.; Edgerton, E.; Fry, J. L.; Hutzell, W. T.; Schwede, D. B.; Shepson, P. B. Modeling the Current and Future Roles of Particulate Organic Nitrates in the Southeastern United States. Environ. Sci. Technol. 2015, 49, 14195– 14203,  DOI: 10.1021/acs.est.5b03738
      65
      Modeling the Current and Future Roles of Particulate Organic Nitrates in the Southeastern United States
      Pye, Havala O. T.; Luecken, Deborah J.; Xu, Lu; Boyd, Christopher M.; Ng, Nga L.; Baker, Kirk R.; Ayres, Benjamin R.; Bash, Jesse O.; Baumann, Karsten; Carter, William P. L.; Edgerton, Eric; Fry, Juliane L.; Hutzell, William T.; Schwede, Donna B.; Shepson, Paul B.
      Environmental Science & Technology (2015), 49 (24), 14195-14203CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Org. nitrates are an important aerosol constituent in locations where biogenic hydrocarbon emissions mix with anthropogenic NOx sources. While regional and global chem. transport models may include a representation of org. aerosol from monoterpene reactions with NO3- radicals (primary source of particle-phase org. NO3- in the southeastern US), secondary org. aerosol (SOA) models can underestimate yields. SOA parametrizations do not explicitly account for org. NO3- compds. produced in the gas phase. This work developed a coupled gas/aerosol system to describe formation and subsequent aerosol-phase partitioning of org. NO3- from isoprene and monoterpenes, focusing on the southeastern US. Org. aerosol and gas-phase org. NO3- concns. improved when particulate org. NO3- were assumed to undergo rapid (τ = 3 h) pseudo-hydrolysis resulting in HNO3 and non-volatile secondary org. aerosol formation. Also, up to 60% of less oxidized-oxygenated org. aerosol could be accounted for by org. NO3--mediated chem. during the Southern Oxidants and Aerosol Study (SOAS). A 25% redn. in NOx (NO + NO2) emissions was predicted to cause a 9% redn. in org. aerosols for June 2013 SOAS conditions at Centerville, Alabama.

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