Interest and concern about polyfluorinated compounds (PFCs), such as perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and an increasing number of other related compounds is growing as more is learned about these ubiquitous anthropogenic substances. Many of these compounds can be toxic, and they are regularly found in the blood of animals and humans worldwide. A great deal of research has been conducted in this area, but a surprising amount remains unknown about their distribution in the environment and how people ultimately become exposed. The utility of these compounds seems to ensure their continued use in one form or another for the foreseeable future, presenting a long-term challenge to scientists, industry leaders, and public health officials worldwide.

The goal of this article is to summarize new biological monitoring information on perfluorinated compounds (PFCs) in aquatic ecosystems (post-2005) as a followup to our critical review published in 2006. A wider range of geographical locations (e.g., South America, Russia, Antarctica) and habitats (e.g., high-mountain lakes, deep-ocean, and offshore waters) have been investigated in recent years enabling a better understanding of the global distribution of PFCs in aquatic organisms. High concentrations of PFCs continue to be detected in invertebrates, fish, reptiles, and marine mammals worldwide. Perfluorooctane sulfonate (PFOS) is still the predominant PFC detected (mean concentrations up to 1900 ng/g ww) in addition to important concentrations of long-chain perfluoroalkyl carboxylates (PFCAs; sum PFCAs up to 400 ng/g ww). More studies have evaluated the bioaccumulation and biomagnification of these compounds in both freshwater and marine food webs. Several reports have indicated a decrease in PFOS levels over time in contrast to PFCA concentrations that have tended to increase in tissues of aquatic organisms at many locations. The detection of precursor metabolites and isomers has become more frequently reported in environmental assessments yielding important information on the sources and distribution of these contaminants. The integration of environmental/ecological characteristics (e.g., latitude/longitude, salinity, and/or trophic status at sampling locations) and biological variables (e.g., age, gender, life cycle, migration, diet composition, growth rate, food chain length, metabolism, and elimination) are essential elements in order to adequately study the environmental fate and distribution of PFCs and should be more frequently considered in study design.

In comparison to other persistent organic pollutants, human fluorochemical contamination is relatively complicated. This complication arises at least in part from a disparity between the chemicals used commercially and those measured in the environment and humans. Commercial fluorochemical products are dominated by fluorinated polymers used in textile or carpet applications, or fluorosurfactants used in applications ranging from personal care products, leveling and wetting agents, to greaseproofing food-contact materials. Investigations into environmental and human fluorochemical contamination have focused on perfluorinated acids (PFAs), either the perfluorinated carboxylates (PFCAs) or sulfonates (PFSAs). In this review we will present an overview of data related to human fluorochemical exposure including a discussion of fluorochemical production, concentrations in exposure media, biotransformation processes producing PFAs, and trends in human sera. These data will be presented in the context of how they can inform sources of human PFA contamination, specifically whether the contamination results from direct PFA exposure or indirect exposure via the biotransformation of commercial fluorochemicals or their residuals. Concentrations of both perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) began to decrease in human sera around the year 2000, a change that mirrored the 2000–2002 phase-out of perfluorooctane sulfonyl fluoride (POSF) production. These temporal trends suggest exposure to current-use POSF-based materials was a significant source of PFOA and PFOS exposure prior to 2000. Relatively slow PFOA elimination and increasing concentrations of the C9 and C10 PFCAs in human sera suggest continued PFCA exposure, without similar exposure to PFOS, which is consistent with indirect exposure via the biotransformation of fluorotelomer-based materials. Conversely, human exposure models have suggested direct exposure to PFAs present in food items is the major source of human contamination. The data set presented here cannot unequivocally delineate between direct and indirect human exposure, however temporal trends in human sera and exposure media are consistent with indirect exposure representing a significant portion of observed human PFA contamination.

Analytical methods for determining perfluorochemicals (PFCs) and fluorotelomer alcohols (FTOHs) in plants using liquid chromatography/tandem mass spectrometry (LC/MS/MS) and gas chromatography/mass spectrometry (GC/MS) were developed, and applied to quantify a suite of analytes in plants from biosolid-amended fields. Dichloromethane−methanol and ethylacetate were chosen as extracting solutions for PFCs and FTOHs, respectively. Nine perfluorocarboxylic acids (PFCAs), three perfluorosulfonic acids (PFSAs), and ten FTOHs were monitored. Most PFCAs and perfluorooctanesulfonate (PFOS) were quantifiable in plants grown in contaminated soils, whereas PFCs went undetected in plants from two background fields. Perfluorooctanoic acid (PFOA) was a major homologue (∼10−200 ng/g dry wt), followed by perfluorodecanoic acid (∼3−170 ng/g). [PFOS] in plants (1−20 ng/g) generally was less than or equal to most [PFCAs]. The site-specific grass/soil accumulation factor (GSAF = [PFC]_Grass/[PFC]_Soil) was calculated to assess transfer potentials from soils. Perfluorohexanoic acid had the highest GSAF (= 3.8), but the GSAF decreased considerably with increasing PFCA chain length. Log-transformed GSAF was significantly correlated with the PFCA carbon-length (p < 0.05). Of the measured alcohols, 8:2nFTOH was the dominant species (≤1.5 ng/g), but generally was present at ≥10× lower concentrations than PFOA.

Per- and polyfluorinated compounds (PFCs) have been found to be ubiquitously distributed in human populations, however the sources of human exposure are not fully characterized. A wide range of PFCs were determined in paired samples of indoor air and dust from 41 Norwegian households. Up to 18 ionic and 9 neutral PFCs were detected. The concentrations found are comparable to or lower than what has previously been reported in North America, Europe, and Asia. The highest median concentrations in dust were observed for perfluorohexanoic acid (28 ng/g), perfluorononanoic acid (23 ng/g), perfluorododecanoic acid (19 ng/g), and perfluorooctanoic acid (18 ng/g). However, perfluoroalkyl sulfonic acids (PFSAs) were also frequently detected. Fluortelomer alcohols were the most prominent compounds found in indoor air, with median concentrations for 8:2 fluortelomer alcohol, 10:2 fluortelomer alcohol, and 6:2 fluortelomer alcohol of 5173, 2822, and 933 pg/m³ air, respectively. All perfluoroalkyl sulfonamides and sulfonamidoethanols (FOSA/FOSEs) were detected in more than 40% of the air samples. For the first time, significant positive correlations (p < 0.05) between PFSAs in house dust and FOSA/FOSEs in the indoor air have been shown, supporting the hypothesis that FOSA/FOSEs may be transformed to PFSAs. Further, we found the age of the residence to be a predictor of PFC concentrations in both indoor air and house dust. These results are important for estimating the exposure to PFCs from the indoor environment and for characterization of exposure pathways.

Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are widely detected in human blood and serum and are of concern due to their potential toxicity. This study investigated the indoor sources of these compounds and their neutral precursors through a survey of 152 homes in Vancouver, Canada. Samples were collected of indoor air, outdoor air, indoor dust, and clothes dryer lint and analyzed for neutral [i.e., fluorotelomer alcohols (FTOHs), perfluorooctane sulfonamide (FOSA), and perfluorooctane sulfonamidoethanol (FOSE)] and ionic [i.e., PFOS and perfluoroalkyl carboxylates (PFCAs)] poly- and perfluorinated compounds (PFCs). Indoor air was dominated by 8:2 FTOH with a geometric mean concentration (pg/m³) of 2900. Among the FOSAs and FOSEs, MeFOSE exhibited the highest air concentration with a geometric mean of 380 pg/m³. PFOA was the major ionic PFC and was detected in all indoor air samples with a geometric mean of 28 pg/m³, whereas PFOS was below the detection limit. The results for the ionic PFCs in indoor air are the first for North America. The pattern of the neutral PFCs in house dust was also dominated by 8:2 FTOH, with a geometric mean of 88 ng/g. Dusts were enriched (relative to air) with sulfonamidoethanol (FOSE) which comprised ∼22% of the total neutral PFC content compared to only ∼3% in air. PFOS and PFOA were the most prominent compounds detected in dust samples. Levels of neutral PFCs in clothes dryer lint were an order of magnitude lower compared to house dust. Human exposure estimates to PFCs for adults and children showed that inhalation was the main exposure route for neutral and ionic PFCs in adults. For toddlers, ingestion of PFCs via dust was more relevant and was on the order of a few mg/day. Results from this study contribute to our understanding of exposure pathways of PFCs to humans. This will facilitate investigations of related health effects and human monitoring data.

Models for assessing intakes of perfluorooctanoic acid, PFOA, are described and applied. One model is based on exposure media concentrations and contact rates. This model is applied to general population exposures for adults and 2-year old children. The other model is a simple one-compartment, first-order pharmacokinetic (PK) model. Parameters for this model include a rate of elimination of PFOA and a blood volume of distribution. The model was applied to data from the National Health and Nutritional Examination Survey, NHANES, to backcalculate intakes. The central tendency intake estimate for adults and children based on exposure media concentrations and contact rates were 70 and 26 ng/day, respectively. The central tendency adult intake derived from NHANES data was 56 and 37 ng/day for males and females, respectively. Variability and uncertainty discussions regarding the intake modeling focus on lack of data on direct exposure to PFOA used in consumer products, precursor compounds, and food. Discussions regarding PK modeling focus on the range of blood measurements in NHANES, the appropriateness of the simple PK model, and the uncertainties associated with model parameters. Using the PK model, the 10th and 95th percentile long-term average adult intakes of PFOA are 15 and 130 ng/day.

Perfluorinated chemicals (PFCs) such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have been produced and used in a wide range of industrial and consumer products for many decades. Their resistance to degradation has led to their widespread distribution in the environment, but little is known about how humans become exposed. Recent studies have demonstrated that the application of PFC contaminated biosolids can have important effects on local environments, ultimately leading to demonstrable human exposures. This manuscript describes a situation in Decatur, Alabama where PFC contaminated biosolids from a local municipal wastewater treatment facility that had received waste from local fluorochemical facilities were used as a soil amendment in local agricultural fields for as many as twelve years. Ten target PFCs were measured in surface and groundwater samples. Results show that surface and well water in the vicinity of these fields had elevated PFC concentrations, with 22% of the samples exceeding the U.S. Environmental Protection Agency’s Provisional Health Advisory level for PFOA in drinking water of 400 ng/L. Water/soil concentration ratios as high as 0.34 for perfluorohexanoic acid, 0.17 for perfluoroheptanoic acid, and 0.04 for PFOA verify decreasing mobility from soils with increasing chain length while indicating that relatively high transport from soils to surface and well water is possible.

The purpose of this study was to determine the concentration trends of a nine-target-analyte homologous series of perfluorocarboxylates from six American Red Cross adult blood donor centers. A total of 645 serum and 600 plasma samples were obtained in 2000–2001 and 2006, respectively, with samples stratified for each 10-year (20–69) age- and sex-group per each location. Samples were extracted by protein precipitation and quantified by using tandem mass spectrometry. The nine perfluorocarboxylates were perfluorobutanoate (PFBA, C₃F₇CO₂^–), perfluoropentanoate (PFPeA, C₄F₉CO₂^–), perfluorohexanoate (PFHxA, C₅F₁₁CO₂^–), perfluoroheptanoate (PFHpA, C₆F₁₃CO₂^–), perfluorooctanoate (PFOA, C₇F₁₅CO₂^–), perfluorononanoate (PFNA, C₈F₁₇CO₂^–), perfluorodecanoate (PFDA, C₉F₁₉CO₂^–), perfluoroundecanoate (PFUnA,C₁₀F₂₁CO₂^–), and perfluorododecanoate (PFDoA, C₁₁F₂₃CO₂^–). The majority of measurements were less than the lower limit of quantitation for PFPeA, PFHxA, and PFDoA. For the remaining targeted analytes, the geometric mean serum and plasma concentrations (ng/mL) for 2000–2001 and 2006 were, respectively, as follows: PFBA 2.61 vs 0.33, PFHpA 0.13 vs 0.09, PFOA 4.70 vs 3.44, PFNA 0.57 vs 0.97, PFDA 0.16 vs 0.34, and PFUnA 0.10 vs 0.18. Estimates of the 95th percent tolerance limits (ng/mL) were as follows: PFBA 5.3 vs 1.4, PFHpA 0.4 vs 0.4, PFOA 12.3 vs 7.7, PFNA 1.4 vs 2.2, PFDA 0.4 vs 0.8, and PFUnA 0.3 vs 0.5. Important observations were the decline in PFBA and increase in PFNA, PFDA, and PFUnA concentrations between 2000–2001 and 2006. The longer chain length perfluorocarboxylates were also highly correlated with each other.

Perfluorinated carboxylic acids are widely distributed in the environment, including remote regions, but their sources are not well understood. Perfluoropropionic acid (PFPrA, CF₃CF₂C(O)OH) has been observed in rainwater but the observed amounts can not be explained by currently known degradation pathways. Smog chamber studies were performed to assess the potential of photolysis of perfluoro-2-methyl-3-pentanone (PFMP, CF₃CF₂C(O)CF(CF₃)₂), a commonly used fire-fighting fluid, to contribute to the observed PFPrA loadings. The photolysis of PFMP gives CF₃CF₂C·(O) and ·CF(CF₃)₂ radicals. A small (0.6%) but discernible yield of PFPrA was observed in smog chamber experiments by liquid chromatography−mass spectrometry offline chamber samples. The Tropospheric Ultraviolet−Visible (TUV) model was used to estimate an atmospheric lifetime of PFMP with respect to photolysis of 4−14 days depending on latitude and time of year. PFMP can undergo hydrolysis to produce PFPrA and CF₃CFHCF₃ (HFC-227ea) in a manner analogous to the Haloform reaction. The rate of hydrolysis was measured using ¹⁹F NMR at two different pHs and was too slow to be of importance in the atmosphere. Hydration of PFMP to give a geminal diol was investigated computationally using density functional theory. It was determined that hydration is not an important environmental fate of PFMP. The atmospheric fate of PFMP seems to be direct photolysis which, under low NO_x conditions, gives PFPrA in a small yield. PFMP degradation contributes to, but does not appear to be the major source of, PFPrA observed in rainwater.

Since 2002, practices in manufacturing polyfluoroalkyl chemicals (PFCs) in the United States have changed. Previous results from the National Health and Nutrition Examination Survey (NHANES) documented a significant decrease in serum concentrations of some PFCs during 1999−2004. To further assess concentration trends of perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), perfluorohexane sulfonate (PFHxS), and perfluorononanoate (PFNA), we analyzed 7876 serum samples collected from a representative sample of the general U.S. population ≥12 years of age during NHANES 1999−2008. We detected PFOS, PFOA, PFNA, and PFHxS in more than 95% of participants. Concentrations differed by sex regardless of age and we observed some differences by race/ethnicity. Since 1999−2000, PFOS concentrations showed a significant downward trend, because of discontinuing industrial production of PFOS, but PFNA concentrations showed a significant upward trend. PFOA concentrations during 1999−2000 were significantly higher than during any other time period examined, but PFOA concentrations have remained essentially unchanged during 2003−2008. PFHxS concentrations showed a downward trend from 1999 to 2006, but concentrations increased during 2007−2008. Additional research is needed to identify the environmental sources contributing to human exposure to PFCs. Nonetheless, these NHANES data suggest that sociodemographic factors may influence exposure and also provide unique information on temporal trends of exposure.

Perfluorinated compounds (PFCs) were measured in fish samples and blood plasma of anglers in a cross-sectional study at Lake Möhne, Sauerland area, Germany. Human plasma and drinking water samples were analyzed by solid phase extraction, high-performance liquid chromatography (HPLC), and tandem mass spectrometry (MS/MS). PFCs in fish fillet were measured by ion pair extraction followed by HPLC and MS/MS. PFOS concentrations in 44 fish samples of Lake Möhne ranged between 4.5 and 150 ng/g. The highest median PFOS concentrations have been observed in perches (median: 96 ng/g) and eels (77 ng/g), followed by pikes (37 ng/g), whitefish (34 ng/g), and roaches (6.1 ng/g). In contrast, in a food surveillance program only 11% of fishes at retail sale contained PFOS at detectable concentrations. One hundred five anglers (99 men, 6 women; 14–88 years old; median 50.6 years) participated in the human biomonitoring study. PFOS concentrations in blood plasma ranged from 1.1 to 650 μg/L (PFOA: 2.1–170 μg/L; PFHxS: 0.4–17 μg/L; LOD: 0.1 μg/L). A distinct dose-dependent relationship between fish consumption and internal exposure to PFOS was observed. PFOS concentrations in blood plasma of anglers consuming fish 2–3 times per month were 7 times higher compared to those without any fish consumption from Lake Möhne. The study results strongly suggest that human internal exposure to PFC is distinctly increased by consumption of fish from PFC-contaminated sites.

Perfluorinated carboxylic acids (PFCAs) are ubiquitous in the environment and have been detected in human blood worldwide. One potential route is direct exposure to PFCAs through contact with polymers that have been fluorinated through a process referred to as direct fluorination. PFCAs are hypothesized to be reaction byproducts of direct fluorination when trace amounts of oxygen are present. The objective of this research was to investigate whether PFCAs could be measured in directly fluorinated high-density polyethylene (HDPE) bottles. PFCAs were quantified using Soxhlet extraction with methanol, followed by LC-MS/MS analysis. Total concentrations of PFCAs ranged from 8.5 ± 0.53 to 113 ± 2.5 ng/bottle (1 L), with the short-chain PFCAs, perfluoropropanoic, perfluorobutanoic, perfluoropentanoic, and perfluorohexanoic acids, being the dominant congeners observed. Relative PFCA concentrations varied depending on fluorination level. Structural isomers were detected using ¹⁹F NMR and are hypothesized to have formed during the fluorination process; NMR data revealed the linear isomer typically comprised 55% of the examined sample. Internally branched, isopropyl branched, and t-butyl PFCA isomers of varying chain length were also identified. Electrochemical fluorination was previously thought to be the only source of branched PFCA isomers. The observation here of branched isomers suggests direct fluorination may be an additional source of exposure to these chemicals. The purpose of this study was to measure PFCAs in directly fluorinated material, serving as a previously unidentified source contributing to the environmental load of PFCAs, with potential for human exposure.

Perfluoroethylcyclohexanesulfonate (PFECHS) is a cyclic perfluorinated acid (PFA) mainly used as an erosion inhibitor in aircraft hydraulic fluids. It is expected to be as recalcitrant to environmental degradation as aliphatic PFAs including perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS). For the first time, PFECHS is reported in top predator fish (<MDL to 3.7 ng g^–1 wet weight in whole body homogenate) from the Great Lakes and in surface waters (0.16–5.7 ng L^–1). PFOS was the major aliphatic PFA in fish from the Great Lakes. Concentrations of most of the PFAs were not statistically different from previously reported 2004 trout data in Lake Ontario. Shorter chain perfluorocarboxylates were prevalent in surface waters of the Great Lakes, dominated by PFOA (0.65–5.5 ng/L). An impurity in the commercial PFECHS formulation, perfluoromethylcyclohexane sulfonate (PFMeCHS), was also detected in the dissolved phase but not above detection limits in fish tissue. Bioaccumulation factors (BAFs) were estimated by taking the ratio of fish to water concentrations. The mean log BAF values corresponded to 2.8 for PFECHS, 2.1 for PFOA, and 4.5 for PFOS. It is not certain whether the fish–water BAF for PFECHS is an overestimate due to the influence of precursor biotransformation. Further studies are recommended to understand the extent of PFECHS contamination.

Human biomonitoring has traditionally focused on analyzing the perfluorocarboxylates (PFCAs) and perfluorosulfonates (PFSAs), although the presence of other unidentified fluorinated chemicals has been demonstrated through total organofluorine analysis. Exposure to legacy and current commercial fluorinated chemicals was investigated by analyzing fifty human sera samples collected in 2009 from the United States for forty fluorinated analytes that included the polyfluoroalkyl phosphate diesters (diPAPs), N-ethyl perfluorooctanesulfonamidoethanol-based polyfluoroalkyl phosphate diester (SAmPAP), one fluorotelomer mercaptoalkyl phosphate diester congener (FTMAP), fluorotelomer sulfonates (FTSs), perfluorophosphonates (PFPAs), and perfluorophosphinates (PFPiAs). DiPAP concentrations (0.035−0.136 μg/L) for the more dominant congeners (6:2, 6:2/8:2, 8:2) were lower than those reported in human sera samples collected in 2004, 2005, and 2008. The SAmPAP and 6:2 FTMAP were not detected, but exposure to SAmPAP was suggested based on the detection of one of its potential degradation intermediates, N-ethyl perfluorooctanesulfonamidoacetate (N-EtFOSAA). PFPiAs were detected for the first time in human sera, with C6/C6 and C6/C8 PFPiAs as the dominant congeners, observed in >50% of the samples.

A fluorochemical industrial park was built in 2004 in Fuxin, China, for the production of polytetrafluoroethylene (PTFE) and perfluorobutane sulfonate (PFBS). Yet little is known about the distribution of fluorochemicals in the environment and in people living in and around the park. In this study, environmental samples were collected from 22 sites in Fuxin to investigate the extent of perfluorinated compound (PFC) contamination in the environment around the park, and in drinking water from the public water supply system and groundwater in shallow aquifers from private wells near the park. Serum samples were also collected from nonoccupationally exposed residents living in Fuxin to determine the PFC load of local residents. As the dominant contaminant of eight target PFCs, the maximum concentrations of perfluorooctanoic acid (PFOA) in sediment and river water of the River Xi along the industrial park were 48 ng/g dry weight and 668 ng/L, respectively; the highest PFOA concentration in groundwater beneath the park was 524 ng/L; and the PFOA levels in drinking water from the public water supply system ranged between 1.3 and 2.7 ng/L. In human serum, PFOA had the geometric mean at 4.3 ng/mL, ranging from 0.02 to 93 ng/mL. This study serves to document what should be the beginning of a long-term surveillance effort to minimize potential exposure of residents living in Fuxin.

Perfluorooctane sulfonate (PFOS; a perfluorinated compound or PFC), its salts, and perfluorooctane sulfonyl fluoride have recently been listed in Annex B of the Stockholm Convention due to their widespread presence, persistence, and toxicity. Because of the persistent nature of PFCs, it is generally presumed that the impact of direct discharges of these chemicals on a receiving environment would be long-lasting. However, long-term environmental fate studies based on field measurements are rare. We examined spatial and long-term (9 year) temporal trends of PFCs in water, sediment, fish, and fish liver collected in 2003, 2006, and 2009 from 10 locations spanning ∼20 km in Etobicoke and Spring Creeks, where an accidental release of fire fighting foam containing PFOS from nearby Toronto International Airport occurred in 2000. Even a decade after the spill, sediment PFOS concentrations are still elevated in Spring Creek Pond which received the foam discharge; however, the major impact is relatively localized likely due to the stormwater management nature of the pond and the diluting effect of Etobicoke Creek. Fish and fish liver PFOS concentrations at a Spring Creek location downstream of Spring Creek Pond declined by about 70 and 85%, respectively, between 2003 and 2009. PFOS in water at locations further downstream in Etobicoke Creek have declined by >99.99% since the spill; however, the 2009 water and fish levels were ∼2–10 times higher than upstream locations likely due to the long-term impact of the spill as well as urbanization. The decrease in the upstream PFOS concentrations likely reflects the reduction of PFOS sources due to phased out production by 3M and regulations on the use of PFOS in fire fighting foams. Field-based sediment/water distribution coefficients (K_D) and bioaccumulation factors (BAF) were calculated from environmental measurements. Log K_D values were 0.54–1.65 for perfluoroalkyl sulfonates (PFASs) and 1.00–1.85 for perfluorocarboxylates (PFCAs). Log BAF_fish ranged from 1.85 to 3.24 for PFASs and 0.88–3.47 for PFCAs, whereas log BAF_{fish liver} ranged from 2.1−4.3 for PFASs and 1.0–5.0 for PFCAs.

Temporal trends of polyfluoroalkyl compounds (PFCs) were examined in tawny owl (Strix aluco) eggs collected in Central Norway over a period of 24 years (1986−2009). Concentrations of 12 PFCs, including C₆−C₈, C₁₀ perfluoroalkyl sulfonates (PFSAs), perfluorooctane sulfonamide (PFOSA), and C₈−C₁₄ perfluoroalkyl carboxylates (PFCAs), were measured, whereas saturated and unsaturated fluorotelomer carboxylates and shorter chain PFSAs and PFCAs were not detected. Perfluorooctane sulfonate (PFOS) was the predominant compound (geometric mean 10.1 ng/g wet weight (ww)), followed by perfluorotridecanoate (PFTriDA) (0.36 ng/g ww) and perfluoroundecanoate (PFUnDA) (0.19 ng/g ww). Significant decreasing concentrations were found for PFOS with an annual decrease of 1.6% (1986−2009), while, conversely, the C₁₀−C₁₃ PFCA concentrations increase significantly with an annual increase of 4.2−12% (1986−2009). Consequently, the contribution of PFOS to the ∑PFCs decreased, whereas the contribution of the ∑PFCAs increased over the time. Toxicological implications for tawny owls are limited, but the maximal PFOS concentration found in this stu0dy is about 20 times lower than the predicted avian no effect concentration (PNEC) which suggest adverse effects caused by PFOS are unlikely. However, tawny owls are exposed to a mixture of various PFCs, and PFCA concentrations still increase.

Polyfluoroalkyl compounds (PFCs) were determined in air around a wastewater treatment plant (WWTP) and two landfill sites using sorbent-impregnated polyurethane foam (SIP) disk passive air samplers in summer 2009. The samples were analyzed for five PFC classes (i.e., fluorotelomer alcohols (FTOHs), perfluorooctane sulfonamides (FOSAs), sulfonamidoethanols (FOSEs), perfluoroalkyl sulfonic acids (PFSAs), and perfluoroalkyl carboxylic acids (PFCAs)) to investigate their concentration in air, composition and emissions to the atmosphere. ∑PFC concentrations in air were 3−15 times higher within the WWTP (2280−24 040 pg/m³) and 5−30 times higher at the landfill sites (2780−26 430 pg/m³) compared to the reference sites (597−1600 pg/m3). Variations in the PFC pattern were observed between the WWTP and landfill sites and even within the WWTP site. For example, FTOHs were the predominant PFC class in air for all WWTP and landfill sites, with 6:2 FTOH as the dominant compound at the WWTP (895−12 290 pg/m³) and 8:2 FTOH dominating at the landfill sites (1290−17 380 pg/m³). Furthermore, perfluorooctane sulfonic acid (PFOS) was dominant within the WWTP (43−171 pg/m³), followed by perfluorobutanoic acid (PFBA) (55−116 pg/m³), while PFBA was dominant at the landfill sites (101−102 pg/m³). It is also noteworthy that the PFCA concentrations decreased with increasing chain length and that the emissions for the even chain length PFCAs outweighed emissions for the odd chain length compounds. Furthermore, highly elevated PFC concentrations were found near the aeration tanks compared to the other tanks (i.e., primary and secondary clarifier) and likely associated with increased volatilization during aeration that may be further enhanced through aqueous aerosol-mediated transport. ∑PFC yearly emissions estimated using a simplified dispersion model were 2560 g/year for the WWTP, 99 g/year for landfill site 1, and 1000 g/year for landfill site 2. These results highlight the important role of WWTPs and landfills as emission sources of PFCs to the atmosphere.

The recent implementation of soil and drinking water screening guidance values for two perfluorochemicals (PFCs), perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) by the U.S. Environmental Protection Agency (EPA), reflects the growing concerns regarding the presence of these persistent and bioaccumulative chemicals in the natural environment. Previous work has established the potential risk to the environment from the land application of industrially contaminated biosolids, but studies focusing on environmental risk from land application of typical municipal biosolids are lacking. Thus, the present study investigated the occurrence and fate of PFCs from land-applied municipal biosolids by evaluating the levels, mass balance, desorption, and transport of PFCs in soils receiving application of municipal biosolids at various loading rates. This study is the first to report levels of PFCs in agricultural soils amended with typical municipal biosolids. PFOS was the dominant PFC in both biosolids (80−219 ng/g) and biosolids-amended soil (2−483 ng/g). Concentrations of all PFCs in soil increased linearly with increasing biosolids loading rate. These data were used to develop a model for predicting PFC soil concentrations in soils amended with typical municipal biosolids using cumulative biosolids loading rates. Mass balance calculations comparing PFCs applied vs those recovered in the surface soil interval indicated the potential transformation of PFC precursors. Laboratory desorption experiments indicated that the leaching potential of PFCs decreases with increasing chain length and that previously derived organic-carbon normalized partition coefficients may not be accurate predictors of the desorption of long-chain PFCs from biosolids-amended soils. Trace levels of PFCs were also detected in soil cores from biosolids-amended soils to depths of 120 cm, suggesting potential movement of these compounds within the soil profile over time and confirming the higher transport potential for short-chain PFCs in soils amended with municipal biosolids.

The transport dynamics of perfluorinated carboxylic acids and sulfonates during snowmelt in the highly urbanized Highland Creek watershed in Toronto, Canada was investigated by analyzing river water, bulk snow, and groundwater, sampled in February and March 2010, by means of liquid chromatography-tandem mass spectrometry. Perfluorohexanoate, perfluorooctanoate, and perfluorooctane sulfonate were dominant in river water, with concentrations of 4.0–14 ng·L^–1, 2.2–7.9 ng·L^–1, and 2.1–6.5 ng·L^–1, respectively. Relatively high levels of perfluorohexanoate may be related to the recent partial replacement in various consumer products of perfluorooctyl substances with shorter-chained perfluorinated compounds (PFCs). Highest PFC concentrations were found within the more urbanized part of the drainage area, suggestive of residential, industrial, and/or traffic-related sources. The riverine flux of PFCs increased during the snowmelt period, but only approximately one-fifth of the increased flux can be attributed to PFCs present in the snowpack, mostly because concentration in snow are generally quite low compared to those in river water. The remainder of the increased flux must be due to the mobilization of PFCs by the high flow conditions prevalent during snowmelt. Run-off behavior was clearly dependent on perfluoroalkyl chain length: Dilution with relatively clean snowmelt water caused a drop in the river water concentrations of short-chain PFCs at high flow during early melting. This prevented an early concentration peak of those water-soluble PFCs within the stream, as could have been expected in response to their early release from a melting snowpack. Instead, concentrations of particle-associated long-chain PFCs in creek water peaked early in the melt, presumably because high flow mobilized contaminated particles from impervious surfaces in the more urbanized areas of the watershed. The ability to enter the subsurface and deeper groundwater aquifers increased with the PFCs′ water solubility, that is, was inversely related to perfluoroalkyl chain length.

The majority of perfluorinated chemicals (PFCs) are of increasing risk to biota and environment due to their physicochemical stability, wide transport in the environment and difficulty in biodegradation. It is necessary to identify and prioritize these harmful PFCs and to characterize their physicochemical properties that govern the solubility, distribution and fate of these chemicals in an aquatic ecosystem. Therefore, available experimental data (10−35 compounds) of three important properties: aqueous solubility (AqS), vapor pressure (VP) and critical micelle concentration (CMC) on per- and polyfluorinated compounds were collected for quantitative structure−property relationship (QSPR) modeling. Simple and robust models based on theoretical molecular descriptors were developed and externally validated for predictivity. Model predictions on selected PFCs were compared with available experimental data and other published in silico predictions. The structural applicability domains (AD) of the models were verified on a bigger data set of 221 compounds. The predicted properties of the chemicals that are within the AD, are reliable, and they help to reduce the wide data gap that exists. Moreover, the predictions of AqS, VP, and CMC of most common PFCs were evaluated to understand the aquatic partitioning and to derive a relation with the available experimental data of bioconcentration factor (BCF).

Wildlife from remote locations have been shown to bioaccumulate perfluorinated compounds (PFCs) in their tissues. Twelve PFCs, consisting of perfluorinated carboxylic (PFCA) and sulfonic (PFSA) acids as well as the perfluorooctane sulfonate (PFOS) precursor perfluorooctane sulfonamide (PFOSA), were measured in livers of 68 beluga whales (Delphinapterus leucas) collected from two subpopulations, Cook Inlet and eastern Chukchi Sea, in Alaska between 1989 and 2006. PFOS and PFOSA were the dominant compounds measured in both beluga stock populations, with overall median concentrations of 10.8 ng/g and 22.8 ng/g, respectively. Long-chain perfluorocarboxylates, PFCAs (9 to 14 carbons), were detected in more than 80% of the samples. Perfluoroundecanoic acid (PFUnA) and perfluorotridecanoic acid (PFTriA) made up a large percentage of the PFCAs measured with median concentrations of 8.49 ng/g and 4.38 ng/g, respectively. To compare differences in location, year, sex, and length, backward stepwise multiple regression models of the individual and total PFC concentrations were used. Spatially, the Cook Inlet belugas had higher concentrations of most PFCAs and PFOS (p < 0.05); however, these belugas had a lower median concentration of PFOSA when compared to belugas from the eastern Chukchi Sea (p < 0.05). Temporal trends indicated most PFCAs, PFHxS, PFOS, and PFOSA concentrations increased from 1989 to 2006 (p < 0.05). Males had significantly higher concentrations of PFTriA, ΣPFCA, and PFOS (p < 0.05). Perfluorononanic acid (PFNA) and PFOS showed a significant decrease in concentration with increasing animal length (p < 0.05). These observations suggest the accumulation of PFCs in belugas is influenced by year, location, sex, and length.

Perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) are used in a variety of industrial and consumer products and have been detected worldwide in human blood. The sources for human exposure are not well described, but dietary intake is suggested as an important source. In this study of 652 Danish men from the Diet, Cancer and Health cohort, we examined intake of 10 major dietary groups, tap water drinks, alcohol consumption, cooking method, geographical area, age, smoking status, and BMI as potential determinants of PFOA and PFOS plasma levels. Living in the Aarhus area was associated with higher PFOA and PFOS plasma levels compared with living in the Copenhagen area, and never smokers had higher levels than current smokers. Frying as compared with other cooking methods was a determinant of PFOA and PFOS levels. BMI and alcohol consumption were inversely associated with both compounds. Among the dietary groups, only intake of eggs was significantly positively associated with PFOS plasma levels. In future studies, PFOA and PFOS levels in air, dust and water samples should be measured to elucidate further the sources of exposure; exposure through diet needs to be studied in greater detail. Our finding of a higher body burden of PFOA and PFOS among never smokers also warrants further evaluation.

Extensive human exposure to perfluoroalkyl compounds (PFAA) together with their persistence and various toxicities have arisen increasing concern. A noninvasive method would improve exposure assessment for large population, especially the children susceptible to contaminants. The aim of the study was to assess the use of PFAA measurements in human nails as a biomarker of exposure to PFAAs. Fingernail, toenail, and blood samples were collected from 28 volunteers. The PFAA concentrations were determined by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Six PFAA were detected in nails, with perfluorooctane sulfonate (PFOS) being the compound with the highest median concentration (33.5 and 26.1 ng/g in fingernail and toenail, respectively). Followed was perfluorononanoate (PFNA), with the median concentrations of 20.4 and 16.8 ng/g, respectively, in fingernail and toenail. Other PFAA detected were perfluorooctanoate (PFOA), perfluorodecanoate (PFDA), perfluorododecanoate (PFDoA), and perfluorotetradecanoate (PFTA), with median levels ranging between 0.19 and 8.94 ng/g. PFOS and PFNA concentrations in fingernail significantly correlated with those in serum. Fingernail PFOS and PFNA levels were 2.8 and 24.4 times, respectively, higher than the serum levels. The accumulation of PFAA in nails, together with its advantages in noninvasive sampling and ability of reflecting long-term exposure, made nails PFAA an attractive biomarker of exposure.

Background: Perfluorinated chemicals (PFCs) have been used widely in consumer products since the 1950s and are currently found at detectable levels in the blood of humans and animals across the globe. In stark contrast to this widespread exposure to PFCs, there is relatively little research on potential adverse health effects of exposure to these chemicals. Objectives: We performed this cross-sectional study to determine if specific blood PFC levels are associated with impaired response inhibition in children. Methods: Blood levels of 11 PFCs were measured in children (N = 83) and 6 PFCs: perfluorooctane sulfonate (PFOS), perfluorohexane sulfate (PFHxS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorooctanesulfonamide (PFOSA), and perfluorodecanoic acid (PFDA) – were found at detectable levels in most children (87.5% or greater had detectable levels). These levels were analyzed in relation to the differential reinforcement of low rates of responding (DRL) task. This task rewards delays between responses (i.e., longer inter-response times; IRTs) and therefore constitutes a measure of response inhibition. Results: Higher levels of blood PFOS, PFNA, PFDA, PFHxS, and PFOSA were associated with significantly shorter IRTs during the DRL task. The magnitude of these associations was such that IRTs during the task decreased by 29–34% for every 1 SD increase in the corresponding blood PFC. Conclusions: This study suggests an association between PFC exposure and children’s impulsivity. Although intriguing, there is a need for further investigation and replication with a larger sample of children.

Animal studies suggest that perfluorocarbons (PFCs) may alter sexual maturation. Relationships of human PFC exposure with puberty are not clear. We conducted a cross-sectional study to investigate whether perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were associated with indicators of sexual maturation in a 2005–2006 survey of residents with PFOA water contamination from the Mid-Ohio Valley. Participants were 3076 boys and 2931 girls aged 8–18 years. They were classified as having reached puberty based on either hormone levels (total >50 ng/dL and free >5 pg/mL testosterone in boys and estradiol >20 pg/mL in girls) or onset of menarche. We estimated the odds of having reached puberty classified by these criteria and the fitted median age of reaching puberty in relation to serum PFOA and PFOS concentrations measured when puberty status was assigned. For boys, there was a relationship of reduced odds of reached puberty (raised testosterone) with increasing PFOS (delay of 190 days between the highest and lowest quartile). For girls, higher concentrations of PFOA or PFOS were associated with reduced odds of postmenarche (130 and 138 days of delay, respectively). In conclusion, our study showed a later age of puberty in this population correlated with PFC concentrations.

Human breath is the gaseous exchange with the blood and thus contains trace organic contaminants and metabolites representative of environmental doses. Sampling and analysis of gaseous components in human breath offers a noninvasive and quick means of qualitatively and quantitatively assessing internalized doses of environmental contaminants. Although the humid and complex nature of breath is a challenge for detection of part-per-trillion to part-per-billion concentrations of environmental contaminants, recent advances in chemical analysis and instrumentation are allowing determination of environmental exposure and disease detection.

Increasing concerns about greenhouse gas (GHG) emissions in the United States have spurred interest in alternate low carbon fuel sources, such as natural gas. Life cycle assessment (LCA) methods can be used to estimate potential emissions reductions through the use of such fuels. Some recent policies have used the results of LCAs to encourage the use of low carbon fuels to meet future energy demands in the U.S., without, however, acknowledging and addressing the uncertainty and variability prevalent in LCA. Natural gas is a particularly interesting fuel since it can be used to meet various energy demands, for example, as a transportation fuel or in power generation. Estimating the magnitudes and likelihoods of achieving emissions reductions from competing end-uses of natural gas using LCA offers one way to examine optimal strategies of natural gas resource allocation, given that its availability is likely to be limited in the future.

In this study, the uncertainty in life cycle GHG emissions of natural gas (domestic and imported) consumed in the U.S. was estimated using probabilistic modeling methods. Monte Carlo simulations are performed to obtain sample distributions representing life cycle GHG emissions from the use of 1 MJ of domestic natural gas and imported LNG. Life cycle GHG emissions per energy unit of average natural gas consumed in the U.S were found to range between −8 and 9% of the mean value of 66 g CO₂e/MJ. The probabilities of achieving emissions reductions by using natural gas for transportation and power generation, as a substitute for incumbent fuels such as gasoline, diesel, and coal were estimated. The use of natural gas for power generation instead of coal was found to have the highest and most likely emissions reductions (almost a 100% probability of achieving reductions of 60 g CO₂e/MJ of natural gas used), while there is a 10–35% probability of the emissions from natural gas being higher than the incumbent if it were used as a transportation fuel. This likelihood of an increase in GHG emissions is indicative of the potential failure of a climate policy targeting reductions in GHG emissions.

The number of electric and electronic equipment (EEE) owned by households has multiplied in the recent decade. We investigate the climate implications of the purchase, use and disposal of EEE by Norwegian households in 2008. While traditionally, large electric appliances such as washing machines, dryers, refrigerators and freezers have been responsible for most of the electricity use in households apart from heating and hot water, our results indicate that computers, TV sets and other electronic equipment are of comparable importance in terms of life-cycle greenhouse gas (GHG) emissions. For this electronic equipment, the GHG emissions caused by manufacturing are equal to or larger than those caused by their electricity use in operation. The production of EEE purchased in 2008 caused on average 1.2 t CO₂e (_÷ ^× 2) per household. The electricity consumption for the use of EEE in 2008 caused between 0.15 and 1.7 t per household, assuming a Norwegian and an EU electricity mix, respectively. Telecoms networks and TV content caused between 0.13 and 0.3 t per household. The purchase rate of electronic products indicates that these products are replaced or down-cycled much more frequently than necessary based on their technical life span. To reduce the carbon footprint of EEE in Norwegian households, the rate of acquisition of new TVs and PCs needs to be reduced and the energy consumption in the production of these products needs to be addressed.

Employing life cycle greenhouse gas (GHG) emissions as a key performance metric in energy and environmental policy may underestimate actual climate change impacts. Emissions released early in the life cycle cause greater cumulative radiative forcing (CRF) over the next decades than later emissions. Some indicate that ignoring emissions timing in traditional biofuel GHG accounting overestimates the effectiveness of policies supporting corn ethanol by 10–90% due to early land use change (LUC) induced GHGs. We use an IPCC climate model to (1) estimate absolute CRF from U.S. corn ethanol and (2) quantify an emissions timing factor (ETF), which is masked in the traditional GHG accounting. In contrast to earlier analyses, ETF is only 2% (5%) over 100 (50) years of impacts. Emissions uncertainty itself (LUC, fuel production period) is 1–2 orders of magnitude higher, which dwarfs the timing effect. From a GHG accounting perspective, emissions timing adds little to our understanding of the climate impacts of biofuels. However, policy makers should recognize that ETF could significantly decrease corn ethanol’s probability of meeting the 20% GHG reduction target in the 2007 Energy Independence and Security Act. The added uncertainty of potentially employing more complex emissions metrics is yet to be quantified.

Worldwide responses to urbanization, expanding populations and climatic change mean biodiverse habitats are replaced with expensive, but necessary infrastructure. Coastal cities support vast expanses of buildings and roads along the coast or on “reclaimed” land, leading to “armouring” of shorelines with walls, revetments and offshore structures to reduce erosion and flooding. Currently infrastructure is designed to meet engineering and financial criteria, without considering its value as habitat, despite artificial shorelines causing loss of intertidal species and altering ecological natural processes that sustain natural biodiversity. Most research on ameliorating these impacts focus on soft-sediment habitats and larger flora (e.g., restoring marshes, encouraging plants to grow on walls). In response to needs for greater collaboration between ecologists and engineers to create infrastructure to better support biodiversity, we show how such collaborations lead to small-scale and inexpensive ecologically informed engineering which reduces loss of species of algae and animals from rocky shores replaced by walls. Adding experimental novel habitats to walls mimicking rock-pools (e.g., cavities, attaching flowerpots) increased numbers of species by 110% within months, in particular mobile animals most affected by replacing natural shores with walls. These advances provide new insights about melding engineering and ecological knowledge to sustain biodiversity in cities.

Determining the major sources of particles that act as cloud condensation nuclei (CCN) represents a critical step in the development of a more fundamental understanding of aerosol impacts on cloud formation and climate. Reported herein are direct measurements of the CCN activity of newly formed ambient particles, measured at a remote rural site in the Sierra Nevada Mountains of Northern California. Nucleation events in the winter of 2009 occurred during two pristine periods following precipitation, with higher gas-phase SO₂ concentrations during the second period, when faster particle growth occurred (7–8 nm/h). Amines, as opposed to ammonia, and sulfate were detected in the particle phase throughout new particle formation (NPF) events, increasing in number as the particles grew to larger sizes. Interestingly, long-range transport of SO₂ from Asia appeared to potentially play a role in NPF during faster particle growth. Understanding the propensity of newly formed particles to act as CCN is critical for predicting the effects of NPF on orographic cloud formation during winter storms along the Sierra Nevada Mountain range. The potential impact of newly formed particles in remote regions needs to be compared with that of transported urban aerosols when evaluating the impact of aerosols on clouds and climate.

Animal manure amended soils often contain large amounts of bioavailable phosphorus (P) and constitute high risk for the deterioration of surface water quality through eutrophication. Current standards set for the safe disposal of animal manure through soil application are based on the assumption that phosphorus in all P sources would behave similarly. The primary objective of this study was to understand the influence of P from several manure and mineral fertilizer sources applied at 0, 50, and 150 mg P kg^–1 on two measures of bioavailable P to six soils of different initial soil test P levels using corn (Zea mays L.) P uptake and an iron oxide strip method for soil analysis (FeO-P). Total net bioavailable P (TNBP) was calculated by subtracting total P uptake by corn after seven consecutive harvests in control treatments that did not receive P from the P uptake from P-amended treatments. Net biovavailable P after the first harvest (NBP1) was calculated in a similar fashion but only using data from the first harvest. Significant differences in TNBP and NBP1 were found when comparing P sources. The hog (Sus scrofa) manure had the greatest P bioavailability while turkey (Meleagris gallopava) litter had the lowest among the animal P sources across all soils and levels of P application. Significant differences were also found between soils with the highest amounts of TNBP and NBP1 found in the Woodson soil and lowest detected in the Crete soil for most P sources. The FeO-P method was useful in predicting TNBP from most P sources.

Nonpoint source nitrogen (N) pollution is a leading contributor to U.S. water quality impairments. We combined watershed N mass balances and stable isotopes to investigate fate and transport of nonpoint N in forest, agricultural, and urbanized watersheds at the Baltimore Long-Term Ecological Research site. Annual N retention was 55%, 68%, and 82% for agricultural, suburban, and forest watersheds, respectively. Analysis of δ¹⁵N-NO₃^–, and δ¹⁸O-NO₃^– indicated wastewater was an important nitrate source in urbanized streams during baseflow. Negative correlations between δ¹⁵N-NO₃^– and δ¹⁸O-NO₃^– in urban watersheds indicated mixing between atmospheric deposition and wastewater, and N source contributions changed with storm magnitude (atmospheric sources contributed ∼50% at peak storm N loads). Positive correlations between δ¹⁵N-NO₃^– and δ¹⁸O-NO₃^– in watersheds suggested denitrification was removing septic system and agriculturally derived N, but N from belowground leaking sewers was less susceptible to denitrification. N transformations were also observed in a storm drain (no natural drainage network) potentially due to organic carbon inputs. Overall, nonpoint sources such as atmospheric deposition, wastewater, and fertilizer showed different susceptibility to watershed N export. There were large changes in nitrate sources as a function of runoff, and anticipating source changes in response to climate and storms will be critical for managing nonpoint N pollution.

Determination of the source and form of metals in house dust is important to those working to understand human and particularly childhood exposure to metals in residential environments. We report the development of a synchrotron microprobe technique for characterization of multiple metal hosts in house dust. We have applied X-ray fluorescence for chemical characterization and X-ray diffraction for crystal structure identification using microfocused synchrotron X-rays at a less than 10 μm spot size. The technique has been evaluated by application to archived house dust samples containing elevated concentrations of Pb, Zn, and Ba in bedroom dust, and Pb and As in living room dust. The technique was also applied to a sample of soil from the corresponding garden to identify linkages between indoor and outdoor sources of metals. Paint pigments including white lead (hydrocerussite) and lithopone (wurtzite and barite) are the primary source of Pb, Zn, and Ba in bedroom dust, probably related to renovation activity in the home at the time of sampling. The much lower Pb content in the living room dust shows a relationship to the exterior soil and no specific evidence of Pb and Zn from the bedroom paint pigments. The technique was also successful at confirming the presence of chromated copper arsenate treated wood as a source of As in the living room dust. The results of the study have confirmed the utility of this approach in identifying specific metal forms within the dust.

Exceeding 1.2 million acres (4856 km²) since the 1930s, coastal wetland loss has been the most threatening environmental problem in Louisiana, United States. This study utilized high-resolution LiDAR (Light Detection and Ranging) and DEM (Digital Elevation Model) data sets to assess the risk of potential wetland loss due to future sea level rises, their spatial distribution, and the associated loss of soil organic carbon (SOC) and organic nitrogen (SON) estimated from the State Soil Geographic (STATSGO) Database and National Wetlands Inventory (NWI) digital data. Potential inundation areas were divided into five elevation scales: < 0 cm, 0–50 cm, 50–100 cm, 100–150 cm, and 150–200 cm above mean sea level. The study found that southeastern Louisiana on the Mississippi River Delta, specifically the Pontchartrain and Barataria Basins, are most vulnerable to sea-level rise induced inundation. Accordingly, approximately 42,264,600 t of SOC and 2,817,640 t of SON would be inundated by 2050 using an average wetland SOC density (203 t per hectare) for the inundation areas between 0 and 50 cm. The estimated annual SOC and SON loss from Louisiana’s coast is 17% of annual organic carbon and 6–8% of annual organic nitrogen inputs from the Mississippi River.

Compound-specific isotope analysis (CSIA) can potentially be used to relate vapor phase contamination by volatile organic compounds (VOCs) to their subsurface sources. This field and modeling study investigated how isotope ratios evolve during migration of gaseous chlorinated ethenes across a 18 m thick unsaturated zone of a sandy coastal plain aquifer. At the site, high concentrations of tetrachloroethene (PCE up to 380 μg/L), trichloroethene (TCE up to 31,600 μg/L), and cis-1,2-dichloroethene (cDCE up to 680 μg/L) were detected in groundwater. Chlorinated ethene concentrations were highest at the water table and steadily decreased upward toward the land surface and downward below the water table. Although isotopologues have different diffusion coefficients, constant carbon and chlorine isotope ratios were observed throughout the unsaturated zone, which corresponded to the isotope ratios measured at the water table. In the saturated zone, TCE became increasingly depleted along a concentration gradient, possibly due to isotope fractionation associated with aqueous phase diffusion. These results indicate that carbon and chlorine isotopes can be used to link vapor phase contamination to their source even if extensive migration of the vapors occurs. However, the numerical model revealed that constant isotope ratios are only expected for systems close to steady state.

Polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD) are common flame retardants in polymers and textiles. Recognition of the persistent, bioaccumulative, and toxic properties of PBDEs has prompted reductions in their use. In contrast, HBCD has received less scrutiny. The U.S has historically been a dominant BFR consumer. However, the few publications on HBCD in wildlife here suggest modest levels compared to Asian and European studies. In contrast, the HBCD concentrations we detected in U.S. fish are among the highest reported in the world. The temporal trends observed suggest that HBCD use may have risen, and that of Penta-BDE declined, following the 2004 termination of its U.S. manufacture. For example, Hyco River carp collected in 1999–2002 exhibited a mean ∑HBCD (sum of α-, β- and γ-HBCD) concentration of only 13 ng/g (lipid weight basis), but was 4640 ng/g in fish collected in 2006–2007. In contrast, the mean ∑PBDE level in these same fish decreased from 40,700 ng/g in 1999–2002 to 9140 ng/g in 2006–2007. Concentrations of HBCD and PBDEs in several Hyco River fish species exceeded those from rivers less influenced by manufacturing outfalls. Results support the contention that textile-related production, relative to its BFR market share, may release disproportionately large amounts of HBCD to the environment.

A method to determine the depth of buried localized radioactive contamination nonintrusively and nondestructively using principal component analysis is described. The γ-ray spectra from two radionuclides, cesium-137 and cobalt-60, have been analyzed to derive the two principal components that change most significantly as a result of varying the depth of the sources in a bespoke sand-filled phantom. The relationship between depth (d) and the angle (θ) between the first two principal component coefficients has been derived for both cases, viz.d(φ)=x+ylogeφwhere x and y are constants dependent on the shielding material and the γ-ray energy spectrum of the radioactivity in question, and φ is a function of θ. The technique enables the depth of a localized radioactive source to be determined nonintrusively in the range 5 to 50 mm with an accuracy of ±1 mm.

Solvent-extractable monomeric methoxyphenols in aerosol samples conventionally have been used to indicate the influence of biomass combustion. In addition, the presence of lignin oxidation products (LOP), derived from the CuO oxidation of vascular plant organic matter, can help trace the source and inputs of primary biological particles in aerosols. Ambient aerosols (coarse and fine) collected in Houston during summer 2010 were analyzed by gas chromatography–mass spectrometry to characterize monomeric and polymeric sources of LOPs. This is the first time polymeric forms of the LOPs have been characterized in ambient aerosols. The absence or small concentrations of solvent-extractable monomeric LOPs and levoglucosan isomers point to the limited influence of biomass burning during the sampling period. The trace levels of anhydrosugar concentrations most likely result from long-range transport. This observation is supported by the absence of co-occurring lignin monomers that undergo photochemical degradation during transport. The larger concentration (142 ng m^–3) of lignin polymers in coarse aerosols shows the relative importance of primary biological aerosol particles, even in the urban atmosphere. The LOP parameters suggest a predominant influence from woody tissue of angiosperms, with minor influence from soft tissues, gymnosperms, and soil organic matter.

Rapid detection and delineation of contaminants in urban settings is critically important in protecting human health. Cores from trees growing above a plume of contaminated groundwater in Verl, Germany, were collected in 1 day, with subsequent analysis and plume mapping completed over several days. Solid-phase microextraction (SPME) analysis was applied to detect tetrachloroethene (PCE) and trichloroethene (TCE) to below nanogram/liter levels in the transpiration stream of the trees. The tree core concentrations showed a clear areal correlation to the distribution of PCE and TCE in the groundwater. Concentrations in tree cores were lower than the underlying groundwater, as anticipated; however, the tree core water retained the PCE:TCE signature of the underlying groundwater in the urban, populated area. The PCE:TCE ratio can indicate areas of differing degradation activity. Therefore, the phytoscreening analysis was capable not only of mapping the spatial distribution of groundwater contamination but also of delineating zones of potentially differing contaminant sources and degradation. The simplicity of tree coring and the ability to collect a large number of samples in a day with minimal disruption or property damage in the urban setting demonstrates that phytoscreening can be a powerful tool for gaining reconnaissance-level information on groundwater contaminated by chlorinated solvents. The use of SPME decreases the detection level considerably and increases the sensitivity of phytoscreening as an assessment, monitoring, and phytoforensic tool. With rapid, inexpensive, and noninvasive methods of detecting and delineating contaminants underlying homes, as in this case, human health can be better protected through screening of broader areas and with far faster response times.

Using ¹⁴C- and ¹³C-ring-labeling, degradation of five p-nonylphenol (4-NP) isomers including four branched (4-NP₃₈, 4-NP₆₅, 4-NP₁₁₁, and 4-NP₁₁₂) and one linear (4-NP₁) isomers in a rice paddy soil was studied under oxic conditions. Degradation followed an availability-adjusted first-order kinetics with the decreasing order of half-life 4-NP₁₁₁ (10.3 days) > 4-NP₁₁₂ (8.4 days) > 4-NP₆₅ (5.8 days) > 4-NP₃₈ (2.1 days) > 4-NP₁ (1.4 days), which is in agreement with the order of their reported estrogenicities. One metabolite of 4-NP₁₁₁ with less polarity than the parent compound occurred rapidly and remained stable in the soil. At the end of incubation (58 days), bound residues of 4-NP₁₁₁ amounted to 54% of the initially applied radioactivity and resided almost exclusively in the humin fraction of soil organic matter, in which chemically humin-bound residues increased over incubation. Our results indicate an increase of specific estrogenicity of the remaining 4-NPs in soil as a result of the isomer-specific degradation and therefore underline the importance of understanding the individual fate (including degradation, metabolism, and bound-residue formation) of isomers for risk assessment of 4-NPs in soil. 4-NP₁ should not be used as a representative of 4-NPs for studies on their environmental behavior.

The biotransformation potential of six nitrosamines and their precursor secondary amines by a mixed methanogenic culture was investigated. Among the six nitrosamines tested, N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA), and N-nitrosopyrrolidine (NPYR) were almost completely degraded but only when degradable electron donors were available. On the contrary, N-nitrosodiethylamine (NDEA), N-nitrosodipropylamine (NDPA), and N-nitrosodibutylamine (NDBA) were not degraded. Three precursor secondary amines, corresponding to the three biodegradable nitrosamines, were also completely utilized even with very low levels of available electron donors. The secondary amine precursors of the three, nonbiodegradable nitrosamines were also recalcitrant. A bioassay conducted to elucidate the biotransformation pathway of NDMA in the mixed methanogenic culture using H₂ as the electron donor showed that NDMA was utilized as an electron acceptor and transformed to dimethylamine (DMA), which in turn was degraded to ammonia and methane. The H₂ threshold concentration for NDMA bioreduction ranged between 0.0017 and 0.031 atm. Such a high H₂ threshold concentration suggests that in mixed methanogenic cultures, NDMA reducers are weak competitors to other, H₂-consuming microbial species, such as homoacetogens and methanogens. Thus, complete removal of nitrosamines in anaerobic digestion systems, where the H₂ partial pressure is typically below 10^–4 atm, is difficult to achieve.

In vitro incubations of rat cytochrome P-450 (CYP) 2B1 isozyme with three chiral polychlorinated biphenyl (PCB) congeners (PCBs 45, 95, and 132) were performed to investigate factors affecting phase I stereoselective biotransformation. Rat CYP2B1 preferentially biotransformed the second-eluting atropisomers of PCBs 45 and 95 at low substrate concentration ranges (≤15 μM). Biotransformation competition by different congeners was also observed, with increasing competition at higher chlorination. Competition decreased the biotransformation rates of each congener stereoselectively, affecting atropisomeric composition. No atropisomeric enrichment was observed for PCB 132 upon incubation of the racemate. However, under the same conditions, significant differences in biotransformation kinetics were observed in individual atropisomer incubations, indicating that (+)-PCB 132 and (-)-PCB 132 were competitively biotransformed. Homology modeling and docking studies suggested that each atropisomer had different interactions with rat CYP2B1 and could dock with the isozyme at different locations. This is one possible explanation for stereoselective biotransformation and competition of chiral PCBs at the molecular level. Our results suggest that the lack of predictive capability for stereoselectivity of PCBs and other chiral pollutants in biota may be due to competitive and/or inhibitory activities of different substrates, including individual enantiomers of the same compound.

Laboratory column experiments for colloidal transport and retention are often carried out with flow direction oriented against gravity (up-flow) to minimize retention of trapped air. However, the models that underlie colloidal filtration theory (e.g., unit cell models such as the Happel sphere-in-cell and hemispheres-in-cell) typically set flow in the same direction as gravity (down-flow). We performed unit model simulations and experimental observations of retention of colloids with different size and density in porous media in the absence of energy barriers under both up-flow and down-flow conditions. Unit cell models predicted very different deposition (e.g., for large or dense colloids with gravity number N_G > 0.01 at pore water velocity of 4 m/day) under down-flow versus up-flow conditions, which reflect underlying influences of gravity and flow on simulated colloid trajectories that resulted in very different distributions of attached colloids over the model surfaces. The Happel sphere-in-cell model showed greater sensitivity to flow orientation relative to gravity than the hemispheres-in-cell model. In contrast, experimental results were relatively insensitive to orientation of flow with respect to gravity, as a result of the variety of orientations of flow relative to gravity and to the porous media surface that exist in actual porous media. Notably, the down-flow simulations corresponded most closely to the experimental results (for near neutrally buoyant colloids); which justifies the common practice of comparing up-flow experiments to theoretical predictions developed for down-flow conditions.

Leaching behavior of Sr and Cs in the vadose zone of Hanford site (Washington) was studied with laboratory-weathered sediments mimicking realistic conditions beneath the leaking radioactive waste storage tanks. Unsaturated column leaching experiments were conducted using background Hanford pore water focused on first 200 pore volumes. The weathered sediments were prepared by 6 months reaction with a synthetic Hanford tank waste leachate containing Sr and Cs (10^–5 and 10^–3 molal representative of LO- and HI-sediment, respectively) as surrogates for ⁹⁰Sr and ¹³⁷Cs. The mineral composition of the weathered sediments showed that zeolite (chabazite-type) and feldspathoid (sodalite-type) were the major byproducts but different contents depending on the weathering conditions. Reactive transport modeling indicated that Cs leaching was controlled by ion-exchange, while Sr release was affected primarily by dissolution of the secondary minerals. The later release of K, Al, and Si from the HI-column indicated the additional dissolution of a more crystalline mineral (cancrinite-type). A two-site ion-exchange model successfully simulated the Cs release from the LO-column. However, a three-site ion-exchange model was needed for the HI-column. The study implied that the weathering conditions greatly impact the speciation of the secondary minerals and leaching behavior of sequestrated Sr and Cs.

Stable carbon isotope fractionation is a valuable tool for monitoring natural attenuation and to establish the fate of groundwater contaminants. In this study, we measured carbon isotope fractionation during aerobic and anaerobic degradation of two chlorinated benzenes: monochlorobenzene (MCB) and 1,2,4-trichlorobenzene (1,2,4-TCB). MCB isotope fractionation was measured in anaerobic methanogenic microcosms, while 1,2,4-TCB isotope experiments were carried out in both aerobic and anaerobic microcosms. Large isotope fractionation was observed in both the anaerobic microcosm experiments. Enrichment factors (ε) for anaerobic reductive dechlorination of MCB and 1,2,4-TCB were −5.0‰ ± 0.2‰ and −3.0‰ ± 0.4‰, respectively. In contrast, no significant isotope fractionation was found during aerobic microbial degradation of 1,2,4-TCB. The cleavage of a C–Cl σ bond occurs during anaerobic reductive dechlorination of MCB and 1,2,4-TCB, while no σ bond cleavage is involved during aerobic degradation via dioxygenase. The difference in isotope fractionation for aerobic versus anaerobic biodegradation of MCB and 1,2,4-TCB can be explained by the difference in the initial step of aerobic versus anaerobic biodegradation pathways.

Rice cultivated on arsenic (As) contaminated-soils will accumulate variable grain-As concentrations, as impacted by varietal differences, soil variables, and crop management. A field-scale experiment was conducted to study the impact of intermittent and continuous flooding on As speciation and microbial populations in rice rhizosphere compartments of soils that were either historically amended with As pesticide or unamended with As. Rhizosphere-soil, root-plaque, pore-water and grain As were quantified and speciated, and microbial populations in rhizosphere soil and root-plaque were characterized. Total-As concentrations in rhizosphere and grain were significantly lower in intermittently flooded compared to the continuously flooded plots (86% lower in pore-water, 55% lower in root-plaque and 41% lower in grain samples). iAs^V, iAs^III, and DMAs^V were the predominant As species detected in rhizosphere-soil and root-plaque, pore-water and grain samples, respectively. Relative proportions of Archaea and iron-reducing bacteria (FeRB) were higher in rhizosphere soil compared to root-plaque. In rhizosphere soil, the relative abundance of FeRB was lower in intermittently flooded compared to continuously flooded plots, but there were no differences between root-plaque samples. This study has demonstrated that reductions in dissolved As concentrations in the rhizosphere and subsequent decreases in grain-As concentration can be attained through water management.

Reduction of U^VI to U^IV as the result of direct or indirect microbial activity is currently being explored for in situ remediation of subsurface U plumes, under the assumption that U^IV solubility is controlled by the low-solubility mineral uraninite (U^IV-dioxide). However, recent characterizations of U in sediments from biostimulated field sites, as well as laboratory U^VI bioreduction studies, report on the formation of U^IV species that lack the U═O₂═U coordination of uraninite, suggesting that phases other than uraninite may be controlling U^IV solubility in environments with complexing surfaces and ligands. To determine the controls on the formation of such nonuraninite U^IV species, the current work studied the reduction of carbonate-complexed U^VI by (1) five Gram-positive Desulfitobacterium strains, (2) the Gram-negative bacteria Anaeromyxobacter dehalogenans 2CP-C and Shewanella putrefaciens CN32, and (3) chemically reduced 9,10-anthrahydroquinone-2,6-disulfonate (AH₂QDS, a soluble reductant). Further, the effects of 0.3 mM dissolved phosphate on U^IV species formation were explored. Extended X-ray absorption fine structure (EXAFS) spectroscopy analysis demonstrated that the addition of phosphate causes the formation of a nonuraninite, phosphate-complexed U^IV species, independent of the biological or abiotic mode of U^VI reduction. In phosphate-free medium, U^VI reduction by Desulfitobacterium spp. and by AH₂QDS resulted in nonuraninite, carbonate-complexed U^IV species, whereas reduction by Anaeromyxobacter or Shewanella yielded nanoparticulate uraninite. These findings suggest that the Gram-positive Desulfitobacterium strains and the Gram-negative Anaeromyxobacter and Shewanella species use distinct mechanisms to reduce U^VI.

The risk of groundwater contamination by microbial pathogens is linked to their survival in the subsurface. Although there is a large body of literature on the inactivation behavior of suspended (planktonic) microorganisms, little is known about the inactivation of bacteria when attached to sand grain surfaces in groundwater aquifers. The main goal of this study was to develop a fluorescence-based experimental technique for evaluating the extent of inactivation over time of bacteria adhered onto a surface in an aqueous environment. Key features of the developed technique are as follows: (i) attached cells do not need to be removed from the surface of interest for quantification, (ii) bacterial inactivation can be examined in real-time for prolonged time periods, and (iii) the system remains undisturbed (i.e., the aqueous environment is unchanged) during the assay. A negatively or positively charged substrate (i.e., bare or coated glass slide) was mounted in a parallel-plate flow cell, bacteria were allowed to attach onto the substrate, and the loss of bacterial membrane integrity and respiratory activity were investigated as a function of time by fluorescence microscopy using Live/Dead BacLight and BacLight RedoxSensor CTC (5-cyano-2,3-ditolyl tetrazolium chloride) viability assays. These two different measures of bacterial inactivation result in comparable trends in bacterial inactivation, confirming the validity of the experimental technique. The results of this work show that the developed technique is sensitive enough to distinguish between the inactivation kinetics of different representative bacteria attached to either a negatively charged (bare glass) surface or a positively charged (coated glass) surface. Hence, the technique can be used to characterize bacterial inactivation kinetics when attached to environmentally relevant surfaces over a broad range of groundwater chemistries.

Microscale energetic residues (<1 mm) are produced during munitions detonation and the weathering of larger residues, and may serve as mobile and fast dissolving sources of explosive compounds, such as 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). Knowledge of the behavior of microscale energetic residues in subsurface environments is quite limited. This work employed a previously unreported property of TNT, RDX, and HMX (i.e., autofluorescence under 405 nm laser illumination) to visualize and quantify the dissolution of microscale physically attrited energetic residues in saturated porous media. The results demonstrated that within the Composition B particles, TNT dissolved preferentially over RDX/HMX and the mass ratio of RDX/HMX to TNT increased by >5.3 times initially. The focused particles dissolved in a stepwise fashion, with >72% of particle volume reduction in <36 min. Moreover, the results suggested that the particle shape factor was relatively stable and the particles retained their highly irregular shape throughout the dissolution processes. This is the first work to demonstrate application of spectral confocal microscopy for visualizing and quantifying the behavior of energetic residues at the pore-scale.

Intimate coupling of photocatalysis and biodegradation (ICPB) offers potential for degrading biorecalcitrant and toxic organic compounds. This study reports on a novel sponge-type, TiO₂-coated biofilm carrier that showed significant adherence of TiO₂ and ability to accumulate biomass in its interior. This carrier was tested for ICPB in a continuous-flow photocatalytic circulating-bed biofilm reactor (PCBBR) to mineralize 2,4,5-trichlorophenol (TCP), which is biorecalcitrant. Four mechanisms possibly acting in ICPB were tested separately: TCP adsorption to the carrier, UV photolysis, UV photocatalysis, and biodegradation by biofilm inside the carrier. The carrier exhibited strong TCP adsorption that followed a Freundlich isotherm with an exponent near 2. Whereas UV photolysis was negligible, photocatalysis produced TCP-degradation products that could be mineralized, and the strong adsorption of TCP to the carrier enhanced biodegradation by relieving toxicity. Validating the ICPB concept, biofilm was protected inside the carriers, although biomass originally on the outer surface of the carriers was eliminated. ICPB significantly lowered the diversity of the bacterial community, but five genera known to biodegrade chlorinated phenols (Ralstonia, Bradyrhizobium, Methylobacterium, Cupriavidus, and Pandoraea) were markedly enriched.

Our previous study demonstrated that many commercial activated carbon (AC) particles may catalyze transformation of secondary amines to yield trace levels of N-nitrosamines under ambient aerobic conditions. Because of the widespread usage of AC materials in numerous analytical and environmental applications, it is imperative to understand the reaction mechanism responsible for formation of nitrosamine on the surface of ACs to minimize their occurrence in water treatment systems and during analytical methods employing ACs. The study results show that the AC-catalyzed nitrosamine formation requires both atmospheric oxygen and nitrogen. AC’s surface reactive sites react with molecular oxygen to form reactive oxygen species (ROS), which facilitate fixation of molecular nitrogen on the carbon surfaces to generate reactive nitrogen species (RNS) likely nitrous oxide and hydroxylamine that can react with adsorbed amines to form nitrosamines. AC’s properties play a crucial role as more nitrosamine formation is associated with carbon surfaces with higher surface area, more surface defects, reduced surface properties, higher O₂ uptake capacity, and higher carbonyl group content. This study is a first of its kind on the nitrosamine formation mechanism involving nitrogen fixation on AC surfaces, and the information will be useful for minimization of nitrosamines in AC-based processes.

Observations of polychlorinated biphenyls (PCB) concentrations in fluvial surface sediments near the mouths of the six Great Arctic Rivers (GARs; Ob, Yenisey, Lena, Indigirka, Kolyma, and Mackenzie) were combined with annual dissolved organic carbon (DOC) and particulate organic carbon (POC) loadings and hydraulic discharge to estimate the pan-Arctic river flux of PCBs. The highest total-phase fluxes of ∑₁₃PCB were found for the Ob River, with 184 kg/yr and the smallest for the Indigirka River with 3.9 kg/yr. Consistent with a continent-scale trend among the Eurasian GARs of increasing POC concentrations eastward, which is extending to the North American Mackenzie River, a general shift in the estimated PCB partitioning from dissolved to particle-associated flux was found toward the east. Pentachlorinated and hexachlorinated PCBs constituted the majority (>70%) of the total PCB fluxes in the Eurasian Rivers. In contrast, trichlorinated and tetrachlorinated congeners were the most abundant in the Mackenzie (≈ 75%). The total ∑₁₃PCB fluxes from the pan-Arctic rivers are here estimated to be ∼0.4 tonne/yr. This is geochemically consistent with the inventory of total PCBs in the Polar Mixed Layer of the entire Arctic Ocean (0.39 tonne) and about a factor 2 less than two new estimates of the PCB settling export to Arctic subsurface waters. Hence, the yearly Great Arctic River PCB fluxes only represent 0.001% of the historical PCB emission into the global environment. To our knowledge, this is the first estimate of circum-Arctic river flux of any organic pollutant based on a comprehensive investigation of the pollutants in several rivers and it contributes toward a more complete understanding of large-scale contaminant cycling in the Arctic.

Humic substances play a key role in biogeochemical and pollutant redox reactions. The objective of this work was to characterize the proton and electron transfer equilibria of the reducible moieties in different humic acids (HA). Cyclic voltammetry experiments demonstrated that diquat and ethylviologen mediated electron transfer between carbon working electrodes and HA. These compounds were used also to facilitate attainment of redox equilibria between redox electrodes and HA in potentiometric E_h measurements. Bulk electrolysis of HA combined with pH-stat acid titration demonstrated that electron transfer to the reducible moieties in HA also resulted in proton uptake, suggesting decreasing reduction potentials E_h of HA with increasing pH. This was confirmed by potentiometric E_h-pH titrations of HA at different redox states. E_h measurements of HA samples prereduced to different redox states by bulk electrolysis revealed reducible moieties in HA that cover a wide range of apparent standard reduction potentials at pH 7 from E_h⁰* = +0.15 to −0.3 V. Modeling revealed an overall increase in the relative abundance of reducible moieties with decreasing E_h. The wide range of HA is consistent with its involvement in numerous environmental electron transfer reactions under various redox conditions.

A fully kinetic biogeochemical model of sequential reductive dechlorination (SERD) occurring in conjunction with lactate and propionate fermentation, iron reduction, sulfate reduction, and methanogenesis was developed. Production and consumption of molecular hydrogen (H₂) by microorganisms have been modeled using modified Michaelis–Menten kinetics and has been implemented in the geochemical code PHREEQC. The model have been calibrated using a Shuffled Complex Evolution Metropolis algorithm to observations of chlorinated solvents, organic acids, and H₂ concentrations in laboratory batch experiments of complete trichloroethene (TCE) degradation in natural sediments. Global sensitivity analysis was performed using the Morris method and Sobol sensitivity indices to identify the most influential model parameters. Results show that the sulfate concentration and fermentation kinetics are the most important factors influencing SERD. The sensitivity analysis also suggests that it is not possible to simplify the model description if all system behaviors are to be well described.

China has become the world’s largest emitter of SO₂ since 2005, and aggressive deployment of flue gas desulfurization (FGD) at coal-fired power plants appeared in China when facing the formidable pressure of environment pollution. In this work, we estimate the annual emission from combustion sources at provincial levels in China from 1990 to 2007, with updated data investigations. We have implemented the method of transportation matrix to gain a better understanding of sulfur content of coal in consuming provinces, which in turn improved the inventory. The total emissions from combustion in 2007 were 28.3 Tg, half of which was contributed by coal-fired power plants. Meanwhile, the industrial boiler coal combustion and residential coal consumed in centralized heating were responsible for another 32% of the total emissions. From 1990 to 2007, annual SO₂ emission was fluctuated with two peaks (1996 and 2006), and total emission doubled from 15.4 Tg to 30.8 Tg, at an annual growth rate of 4.4% (6.3% since 2000). Due to the extensive application of FGD technology and the phase-out of small, high emitting units, the SO₂ emission began to decrease after 2006. Furthermore, the differences among estimates reported in literatures highlight a great need for further research to reduce the uncertainties with more detailed information on key sources and actual operation of devices.

The stabilizing effect of water molecule bridges on polar regions in humic substances (HSs) has been investigated by means of molecular dynamics (MD) simulations. The purpose of these investigations was to show the effect of water molecular bridges (WAMB) for cross-linking distant locations of hydrophilic groups. For this purpose, a tetramer of undecanoid fatty acids connected to a network of water molecules has been constructed, which serve as a model for spatially fixed aliphatic chains in HSs terminated by a polar (carboxyl) group. The effect of environmental polarity has been investigated by using solvents of low and medium polarity in force-field MD. A nonpolar environment simulated by n-hexane was chosen to mimic the stability of WAMB in a hydrophilic hotspot surrounded by a nonpolar environment, while the more polar acetonitrile environment was chosen to simulate a more even distribution of polarity around the carboxylic groups and the water molecules. The dynamics simulations show that the rigidity of the oligomer chains is significantly enhanced as soon as the water cluster is large enough to comprise all four carboxyl groups. Increasing the temperature leads to evaporization processes which destabilize the rigidity of the tetramer-water cluster. Embedding it into the nonpolar environment introduces a pronounced cage effect which significantly impedes removal of water molecules from the cluster region. On the other hand, a polar environment facilitates their diffusion from the polar region. One important consequence of these simulations is that although the local water network is the stabilizing factor for the organic matter matrix, the degree of stabilization is additionally affected by the presence of nonpolar surroundings.

The pH dependency of soluble phosphate in soil was measured for six agricultural soils over a pH range of 3–10. A mechanistic model, the LCD (ligand charge distribution) model, was used to simulate this change, which considers phosphate adsorption to metal (hydr)oxides in soils under the influence of natural organic matter (NOM) and polyvalent cations (Ca²⁺, Al³⁺, and Fe³⁺). For all soils except one, the description in the normal pH range 5–8 is good. For some soils at more extreme pH values (for low P-loading soils at low pH and for high P-loading soils at high pH), the model over predicts soluble P. The calculation shows that adsorption is the major mechanism controlling phosphate solubility in soils, except at high pH in high P-loading soils where precipitation of calcium phosphate may take place. NOM and polyvalent cations have a very strong effect on the concentration level of P. The pattern of pH dependency of soluble P in soils differs greatly from the pH effects on phosphate adsorption to synthetic metal (hydr)oxides in a monocomponent system. According to the LCD model, the pH dependency in soil is mainly caused by the synergistic effects of Ca²⁺ adsorption to oxides. Adsorption of Al³⁺ to NOM adsorbed plays an important role only at a pH < 4.5. Presence of NOM coating strongly competes with phosphate for the adsorption and is an important factor to consider in modeling phosphate adsorption in natural samples.

As models describing human exposure to organic chemicals gain wider use in chemical risk assessment and management, it becomes important to understand their uncertainty. Although evaluation of parameter sensitivity/uncertainty is increasingly common, model uncertainty is rarely assessed. When it is, the assessment is generally limited to a handful of chemicals. In this study, a strategy for more comprehensive model uncertainty assessment was developed. A regulatory model (EUSES) was compared with a research model based on more recent science. Predicted human intake was used as the model end point. Chemical space visualization techniques showed that the extent of disagreement between the models varied strongly with chemical partitioning properties. For each region of disagreement, the primary human exposure vector was determined. The differences between the models’ process algorithms describing these exposure vectors were identified and evaluated. The equilibrium assumption for root crops in EUSES caused overestimations in daily intake of superhydrophobic chemicals (log K_OW > 11, log K_OA > 10), whereas EUSES’s approach to calculating bioaccumulation in fish prey resulted in underestimations for hydrophobic compounds (log K_OW ∼ 6–8). Uptake of hydrophilic chemicals from soil and bioaccumulation of superhydrophobic chemicals in zooplankton were identified as important research areas to enable further reduction of model uncertainty in bioaccumulation models.

The effectiveness of thin-layer sand capping for contaminated sediment management (capping with a layer of thickness comparable to the depth of benthic interactions) is explored through experiments with laboratory-scale microcosms populated with the deposit-feeding oligochaete, Ilyodilus templetoni. Passive sampling of pore water concentrations in the microcosms using polydimethylsiloxane (PDMS)-coated fibers enabled quantification of high-resolution vertical concentration profiles that were used to infer contaminant migration rates and mechanisms. Observed concentration profiles were consistent with models that combine traditional contaminant transport processes (sorption-retarded diffusion) with bioturbation. Predictions of bioaccumulation based on contaminant pore water concentrations within the surface layer of the cap correlated well with observed bioaccumulation (correlation coefficient of 0.92). The results of this study show that thin-layer sand caps of contaminated sediments can be effective at reducing the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) provided the thickness of the cap layer exceeds the depth of organism interaction with the sediments and the pore water concentrations within the biologically active zone remain low (e.g., when molecular diffusion controls transport from the underlying sediment layer).

The exciting discovery that dechlorinating bacteria can use polarized graphite cathodes as direct electron donors in the reductive dechlorination has prompted investigations on the development of novel bioelectrochemical remediation approaches. In this work, we investigated the performance of a bioelectrochemical reactor for the treatment of trichloroethene (TCE). The reactor was continuously operated for about 570 days, at different potentiostatically controlled cathode potentials, ranging from −250 mV to −750 mV vs standard hydrogen electrode. The rate and extent of TCE dechlorination, as well as the competition for the available electrons, were highly dependent on the set cathode potential. When the cathode was controlled at −250 mV, no abiotic hydrogen production occurred and TCE dechlorination (predominantly to cis-DCE and VC), most probably sustained via direct extracellular electron transfer, proceeded at an average rate of 15.5 ± 1.2 μmol e^–/L d. At this cathode, potential methanogenesis was almost completely suppressed and dechlorination accounted for 94.7 ± 0.1% of the electric current (15.0 ± 0.8 μA) flowing in the system. A higher rate of TCE dechlorination (up to 64 ± 2 μmol e^–/L d) was achieved at cathode potentials lower than −450 mV, though in the presence of a very active methanogenesis which accounted for over 60% of the electric current. Remarkably, the bioelectrochemical reactor displayed a stable and reproducible performance even without the supply of organic carbon sources with the feed, confirming long-term viability.

Coagulation/flocculation (CF) by use of alum and cationic polymer polyDADMAC, was performed as a pretreatment for remediation of oil sands process-affected water (OSPW). Various factors were investigated and the process was optimized to improve efficiency of removal of organic carbon and turbidity. Destabilization of the particles occurred through charge neutralization by adsorption of hydroxide precipitates. Scanning electron microscope images revealed that the resultant flocs were compact. The CF process significantly reduced concentrations of naphthenic acids (NAs) and oxidized NAs by 37 and 86%, respectively, demonstrating the applicability of CF pretreatment to remove a persistent and toxic organic fraction from OSPW. Concentrations of vanadium and barium were decreased by 67–78% and 42–63%, respectively. Analysis of surface functional groups on flocs also confirmed the removal of the NAs compounds. Flocculation with cationic polymer compared to alum, caused toxicity toward the benthic invertebrate, Chironoums dilutus, thus application of the polymer should be limited.

Removal of hexavalent chromium ions from an aqueous solution by crude tamarind (Tamarindus indica) fruit shell was examined in a rotating packed bed contactor by continuously recirculating a given volume of solution through the bed. Reduction of Cr(VI) to Cr(III) within the biosorbent appeared to be the removal mechanism. Depletion rate of Cr(VI) from, and release of reduced Cr(III) ions into the aqueous phase, was influenced by mass transfer resistance besides pH and packing depth. A mathematical model considering the reduction reaction to be irreversible and incorporating intraparticle and external phase mass transfer resistances represented the experimental data adequately. The study indicated that the limitations of fixed bed contactor operating under terrestrial gravity in intensifying mass transfer rates for this system can be overcome with rotating packed bed due to liquid flow under centrifugal acceleration.

To perform a general assessment of treatment efficiency, a mass balance study was undertaken for two types of constructed wetlands (CWs), planted gravel filters and plant root mat systems, for treating VOC (benzene; MTBE) polluted groundwater under field conditions. Contaminant fate was investigated in the respective water, plant, and atmosphere compartments by determining water and atmospheric contaminant loads and calculating contaminant plant uptake, thereby allowing for an extended efficiency assessment of CWs. Highest total VOC removal was achieved during summer, being pronounced for benzene compared to MTBE. According to the experimental results and the calculations generated by the balancing model, degradation in the rhizosphere and plant uptake accounted for the main benzene removal processes, of 76% and 13% for the gravel bed CW and 83% and 11% for the root mat system. Volatilization flux of benzene and MTBE was low (<5%) for the gravel bed CW, while in the root mat system direct contact of aqueous and gaseous phases favored total MTBE volatilization (24%). With this applied approach, we present detailed contaminant mass balances that allow for conclusive quantitative estimation of contaminant elimination and distribution processes (e.g., total, surface, and phytovolatilization, plant uptake, rhizodegradation) in CWs under field conditions.

Polybrominated diphenyl ethers (PBDEs) are widespread global contaminants due to their extensive usage as flame retardants. Among the 209 PBDE congeners, tetra-brominated diphenyl ether (tetra-BDE) (congener 47) and penta-BDEs (congeners 99 and 100) are the most abundant, toxic, and bioaccumulative congeners in the environment. However, little is known about microorganisms that carry out debromination of these congeners under anaerobic conditions. In this study, we describe a coculture GY2 consisting of Dehalococcoides and Desulfovibrio spp., which is capable of debrominating ∼1180 nM of congeners 47, 99, and 100 (88–100% removal) to the nonbrominated diphenyl ether at an average rate of 36.9, 19.8, and 21.9 nM day^–1, respectively. Ortho bromines are preferentially removed during the debromination process. The growth of Dehalococcoides links tightly with PBDE debromination, with an estimated growth yield of 1.99 × 10¹⁴ cells per mole of bromide released, while the growth of Desulfovibrio could be independent of PBDEs. The growth-coupled debromination suggests that Dehalococcoides cells in the coculture GY2 are able to respire on PBDEs. Given the ubiquity and recalcitrance of the tetra- and penta-BDEs, complete debromination of these congeners to less toxic end products (e.g. diphenyl ether) is important for the restoration of PBDE-contaminated environments.

Forward osmosis (FO) is a membrane separation technology that has been studied in recent years for application in water treatment and desalination. It can best be utilized as an advanced pretreatment for desalination processes such as reverse osmosis (RO) and nanofiltration (NF) to protect the membranes from scaling and fouling. In the current study the rejection of trace organic compounds (TOrCs) such as pharmaceuticals, personal care products, plasticizers, and flame-retardants by FO and a hybrid FO-RO system was investigated at both the bench- and pilot-scales. More than 30 compounds were analyzed, of which 23 nonionic and ionic TOrCs were identified and quantified in the studied wastewater effluent. Results revealed that almost all TOrCs were highly rejected by the FO membrane at the pilot scale while rejection at the bench scale was generally lower. Membrane fouling, especially under field conditions when wastewater effluent is the FO feed solution, plays a substantial role in increasing the rejection of TOrCs in FO. The hybrid FO-RO process demonstrated that the dual barrier treatment of impaired water could lead to more than 99% rejection of almost all TOrCs that were identified in reclaimed water.

Co_1–xM_xCr₂O₄ (M = Li, Zr; x = 0–0.2) catalysts were prepared via the citric acid method and investigated for catalytic combustion of methane. Substitution at tetrahedral (A) sites with monovalent (Li) or tetravalent (Zr) metal ions led to a decrease or increase of the catalytic activity, respectively. The Co_0.95Zr_0.05Cr₂O₄ catalyst proved to be the most active and its catalytic activity reached 90% of methane conversion at 448 °C, which dropped by 66 °C compared with that of the undoped CoCr₂O₄ catalyst. XRD and Raman results indicated that lithium or zirconium substitution could modify the spinel structure and electronic properties. For lithium-doped catalysts, oxygen deficiency and a strong surface enrichment in lithium and chromium were detected. Zirconium substitution enhanced the reducibility of zirconium-doped catalysts and decreased the strength constant of both the Co–O band and the Cr–O band, which may contribute to the catalytic activity toward methane combustion. In addition, the prevalent catalytic combustion activity of the zirconium-substituted catalysts could be explained by their higher concentration of suprafacial, weakly chemisorbed oxygen.

Removal of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) from aqueous solution has attracted wide attention in light of their environmental persistence, bioaccumulation, and potential toxicity. Although various destructive technologies were developed, removal of PFOX (X = A and S) under mild conditions are still desirable. In this work, multiwalled carbon nanotubes (MWNTs) were applied to remove PFOX in electrochemically assistant adsorption. Electrosorption kinetics and isotherms were investigated relative to open circuit (OC) adsorption and adsorption on powder MWNTs. Compared with powder MWNTs adsorption, the initial adsorption rate (υ₀) of 100 μg/L PFOX at 0.6 V increased 60-fold (PFOA) and 41-fold (PFOS) according to pseudosecond-order kinetics model and the maximum electrosorption capacity (q_m) of PFOX (50 μg/L to 10 mg/L) increased 150-fold (PFOA) and 94-fold (PFOS) simulated with Langmuir model. These significant improvements were assumed to benefit from enhanced electrostatic attraction under electrochemical assistance. Furthermore, the used MWNTs were found to be regenerative and reusable. This work provides not only a new approach to effective removal of perfluorochemicals from aqueous solution but also a low energy-consumption and environmentally-friendly strategy for application of carbon nanotubes in water treatment.

Biologically produced monometallic palladium nanoparticles (bio-Pd) have been shown to catalyze the dehalogenation of environmental contaminants, but fail to efficiently catalyze the degradation of other important recalcitrant halogenated compounds. This study represents the first report of biologically produced bimetallic Pd/Au nanoparticle catalysts. The obtained catalysts were tested for the dechlorination of diclofenac and trichlorethylene. When aqueous bivalent Pd(II) and trivalent Au(III) ions were both added to concentrations of 50 mg L^–1 and reduced simultaneously by Shewanella oneidensis in the presence of H₂, the resulting cell-associated bimetallic nanoparticles (bio-Pd/Au) were able to dehalogenate 78% of the initially added diclofenac after 24 h; in comparison, no dehalogenation was observed using monometallic bio-Pd or bio-Au. Other catalyst-synthesis strategies did not show improved dehalogenation of TCE and diclofenac compared with bio-Pd. Synchrotron-based X-ray diffraction, (scanning) transmission electron microscopy and energy dispersive X-ray spectroscopy indicated that the simultaneous reduction of Pd and Au supported on cells of S. oneidensis resulted in the formation of a unique bimetallic crystalline structure. This study demonstrates that the catalytic activity and functionality of possibly environmentally more benign biosupported Pd-catalysts can be improved by coprecipitation with Au.

A novel electro-Fenton process was developed for wastewater treatment using a modified divided electrolytic system in which H₂O₂ was generated in situ from electro-generated H₂ and O₂ in the presence of Pd/C catalyst. Appropriate pH conditions were obtained by the excessive H⁺ produced at the anode. The performance of the novel process was assessed by Rhodamine B (RhB) degradation in an aqueous solution. Experimental results showed that the accumulation of H₂O₂ occurred when the pH decreased and time elapsed. The maximum concentration of H₂O₂ reached 53.1 mg/L within 120 min at pH 2 and a current of 100 mA. Upon the formation of the Fenton reagent by the addition of Fe²⁺, RhB degraded completely within 30 min at pH 2 with a pseudo first order rate constant of 0.109 ± 0.009 min^–1. An insignificant decline in H₂O₂ generation and RhB degradation was found after six repetitions. RhB degradation was achieved by the chemisorption of H₂O₂ on the Pd/C surface, which subsequently decomposed into •OH upon catalysis by Pd⁰ and Fe²⁺. The catalytic decomposition of H₂O₂ to •OH by Fe²⁺ was more powerful than that by Pd⁰, which was responsible for the high efficiency of this novel electro-Fenton process.

Glutamic acid is an important constituent of waste streams from biofuels production. It is an interesting starting material for the synthesis of biobased chemicals, thereby decreasing the dependency on fossil fuels. The objective of this paper was to compare the environmental impact of four biobased chemicals from glutamic acid with their petrochemical equivalents, that is, N-methylpyrrolidone (NMP), N-vinylpyrrolidone (NVP), acrylonitrile (ACN), and succinonitrile (SCN). A consequential life cycle assessment was performed, wherein glutamic acid was obtained from sugar beet vinasse. The removed glutamic acid was substituted with cane molasses and ureum. The comparison between the four biobased and petrochemical products showed that for NMP and NVP the biobased version had less impact on the environment, while for ACN and SCN the petrochemical version had less impact on the environment. For the latter two an optimized scenario was computed, which showed that the process for SCN can be improved to a level at which it can compete with the petrochemical process. For biobased ACN large improvements are required to make it competitive with its petrochemical equivalent. The results of this LCA and the research preceding it also show that glutamic acid can be a building block for a variety of molecules that are currently produced from petrochemical resources. Currently, most methods to produce biobased products are biotechnological processes based on sugar, but this paper demonstrates that the use of amino acids from low-value byproducts can certainly be a method as well.

Demonstration-scale metal pouring emission tests and bench-scale Curie-point pyrolysis emission tests were conducted to identify and quantify the hazardous air pollutant (HAP) emissions of five kinds of casting materials, namely, bituminous coal, cellulose, conventional phenolic urethane binder (PUB), naphthalene-depleted PUB, and a collagen-based binder. For a given casting material, the major HAP species generated in Curie-point pyrolysis were essentially the same as those generated in demonstration-scale metal pouring. The 8–10 HAP species identified in the Curie-point pyrolysis tests comprised 65–98% (by weight) of the total HAP emissions quantified in the demonstration-scale pouring emission tests. Furthermore, with these two protocols, we appraised the relative emission changes that would be associated with (a) replacing conventional PUB with collagen-based binder, (b) replacing conventional PUB with naphthalene-depleted PUB, and (c) replacing bituminous coal with cellulose for making sand molds or cores in the casting process. The relative emission changes associated with the use of alternative casting materials exhibited similar trends for most of the major HAP species in the demonstration-scale pouring and Curie-point pyrolysis emission tests. The results indicated that Curie-point pyrolysis emission test could be employed as a convenient and cost-effective screening tool to identify the major HAP species and to compare the relative HAP emission levels for various casting materials.

We describe a flow-through biosensor for online continuous water toxicity monitoring. At the heart of the device are disposable modular biochips incorporating agar-immobilized bioluminescent recombinant reporter bacteria, the responses of which are probed by single-photon avalanche diode detectors. To demonstrate the biosensor capabilities, we equipped it with biochips harboring both inducible and constitutive reporter strains and exposed it to a continuous water flow for up to 10 days. During these periods we challenged the biosensor with 2-h pulses of water spiked with model compounds representing different classes of potential water pollutants, as well as with a sample of industrial wastewater. The biosensor reporter panel detected all simulated contamination events within 0.5–2.5 h, and its response was indicative of the nature of the contaminating chemicals. We believe that a biosensor of the proposed design can be integrated into future water safety and security networks, as part of an early warning system against accidental or intentional water pollution by toxic chemicals.

Our aim was to compare hazards of particles from combustion of biodiesel blends and conventional diesel (D₁₀₀) in old and improved engines. We determined DNA damage in A549 cells, mRNA levels of CCL2 and IL8 in THP-1 cells, and expression of ICAM-1 and VCAM-1 in human umbilical cord endothelial cells (HUVECs). Viability and production of reactive oxygen species (ROS) were investigated in all cell types. We collected particles from combustion of D₁₀₀ and 20% (w/w) blends of animal fat or rapeseed oil methyl esters in light-duty vehicle engines complying with Euro2 or Euro4 standards. Particles emitted from the Euro4 engine were smaller in size and more potent than particles emitted from the Euro2 engine with respect to ROS production and DNA damage, but similarly potent concerning cytokine mRNA expression. Particles emitted from combustion of biodiesel blends were larger in size, and less or equally potent than particles emitted from combustion of D₁₀₀ concerning ROS production, DNA damage and mRNA of CCL2 and IL8. ICAM-1 and VCAM-1 expression in HUVECs was only increased by D₁₀₀ particles from the Euro4 engine. This suggests that particle emissions from biodiesel in equal mass concentration are less toxic than conventional diesel.

Effect-directed analysis (EDA) is an approach used to identify (unknown) contaminants in complex samples which cause toxicity, using a combination of biology and chemistry. The goal of this work was to apply EDA to identify developmental toxicants in soil samples collected from a former municipal landfill site. Soil samples were extracted, fractionated, and tested for developmental effects with an embryotoxicity assay in the zebrafish Danio rerio. Gas chromatograph mass selective detection (GC-MSD) chemical screening was used to reveal candidate developmental toxicants in fractions showing effects. In a parallel study, liquid chromatography–hybrid linear ion trap Orbitrap mass spectrometry was also applied to one polar subfraction (Hoogenboom et al. J. Chromatogr. A2009, 1216, 510–519). EDA resulted in the identification of a number of previously unknown developmental toxicants, which were confirmed to be present in soil by GC-MS. These included 11H-benzo[b]fluorene, 9-methylacridine, 4-azapyrene, and 2-phenylquinoline, as well as one known developmental toxicant (retene). This work revealed the presence of novel contaminants in the environment that may affect vertebrate development, which are not subject to monitoring or regulation under current soil quality assessment guidelines.

Reactive oxygen species (ROS) generated by environmentally persistent free radicals (EPFRs) of 2-monochlorophenol, associated with CuO/silica particles, were detected using the chemical spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy. Yields of hydroxyl radical (^•OH), superoxide anion radical (O₂^•–), and hydrogen peroxide (H₂O₂) generated by EPFR–particle systems were reported. Failure to trap superoxide radicals in aqueous solvent, formed from reaction of EPFRs with molecular oxygen, results from fast transformation of the superoxide to hydrogen peroxide. However, formation of superoxide as an intermediate product in hydroxyl radical formation in aprotic solutions of dimethyl sulfoxide (DMSO) and acetonitrile (AcN) was observed. Experiments with superoxide dismutase (SOD) and catalase (CAT) confirmed formation of superoxide and hydrogen peroxide, respectively, in the presence of EPFRs. The large number of hydroxyl radicals formed per EPFR and monotonic increase of the DMPO–OH spin adduct concentration with incubation time suggest a catalytic cycle of ROS formation.

Amendment of contaminated sediment with activated carbon (AC) is a remediation technique that has demonstrated its ability to reduce aqueous concentrations of hydrophobic organic compounds. The application of AC, however, requires information on possible ecological effects, especially effects on benthic species. Here, we provide data on the effects of AC addition on locomotion, ventilation, sediment avoidance, mortality, and growth of two benthic species, Gammarus pulex and Asellus aquaticus, in clean versus polycyclic aromatic hydrocarbon (PAH) contaminated sediment. Exposure to PAH was quantified using 76 μm polyoxymethylene passive samplers. In clean sediment, AC amendment caused no behavioral effects on both species after 3–5 days exposure, no effect on the survival of A. aquaticus, moderate effect on the survival of G. pulex (LC₅₀ = 3.1% AC), and no effects on growth. In contrast, no survivors were detected in PAH contaminated sediment without AC. Addition of 1% AC, however, resulted in a substantial reduction of water exposure concentration and increased survival of G. pulex and A. aquaticus by 30 and 100% in 8 days and 5 and 50% after 28 days exposure, respectively. We conclude that AC addition leads to substantial improvement of habitat quality in contaminated sediments and outweighs ecological side effects.

For obtaining type approval in the European Union, light-duty vehicles have to comply with emission limits during standardized laboratory emissions testing. Although emission limits have become more stringent in past decades, light-duty vehicles remain an important source of nitrogen oxides and carbon monoxide emissions in Europe. Furthermore, persisting air quality problems in many urban areas suggest that laboratory emissions testing may not accurately capture the on-road emissions of light-duty vehicles. To address this issue, we conduct the first comprehensive on-road emissions test of light-duty vehicles with state-of-the-art Portable Emission Measurement Systems. We find that nitrogen oxides emissions of gasoline vehicles as well as carbon monoxide and total hydrocarbon emissions of both diesel and gasoline vehicles generally remain below the respective emission limits. By contrast, nitrogen oxides emissions of diesel vehicles (0.93 ± 0.39 grams per kilometer [g/km]), including modern Euro 5 diesel vehicles (0.62 ± 0.19 g/km), exceed emission limits by 320 ± 90%. On-road carbon dioxide emissions surpass laboratory emission levels by 21 ± 9%, suggesting that the current laboratory emissions testing fails to accurately capture the on-road emissions of light-duty vehicles. Our findings provide the empirical foundation for the European Commission to establish a complementary emissions test procedure for light-duty vehicles. This procedure could be implemented together with more stringent Euro 6 emission limits in 2014. The envisaged measures should improve urban air quality and provide incentive for innovation in the automotive industry.

Comprehension of the basic concepts for the design of systems for CO₂ adsorption is imperative for increasing interest in technology for CO₂ capture from the effluents. The efficacy of 20 naturally occurring amino acids (AAs) is demonstrated as the most potent CO₂ capturing agents in the process of chemical absorption and physisorption through a systematic computational study using highly parametrized M05–2X/6-311+G(d,p) method. The ability of AAs to bind CO₂ both in the noncovalent and covalent fashion and presence of multiple adsorption sites with varying magnitude of binding strengths in all 20 AAs makes them as most promising materials in the process of physisorption. The binding energies (BEs) estimating the strength of noncovalent interaction of AAs and CO₂ are calculated and results are interpreted in terms of the nature and strength of the various types of cooperative interactions which are present. The study underlines the possibility to engineer the porous solid materials with extended networks by judiciously employing AA chains as linkers which can substantially augment their efficacy. Results show that a significant increase in the CO₂···AA affinity is achieved in the case of AAs with polar neutral side chains. Furthermore, the study proposes AAs as effective alternatives to alkanolamines in chemical dissolution of CO₂.

After anaerobic dark fermentation of waste activated sludge (WAS) for hydrogen production, there are a large number of organic compounds including protein, polysaccharide, and volatile fatty acids left in the dark fermentation liquid, which can be further bioconverted to hydrogen by photofermentation techniquea. In this study, the enhancement of photofermentative hydrogen produced from WAS dark fermentation liquid by using nano-TiO₂ is reported. First, high concentration of NH₄⁺-N in the dark fermentation liquid was observed to inhibit the photofermentative hydrogen production, and its removal was essential. Then the effect of nano-TiO₂ on photofermentative hydrogen generation was investigated, and the addition of 100 mg/L nano-TiO₂ increased hydrogen by 46.1%. Finally, the mechanisms for nano-TiO₂ improving hydrogen production were investigated. It was found that nano-TiO₂ improved the decomposition of protein and polysaccharide to small-molecule organic compounds and promoted the growth of photosynthetic bacteria and the activity of nitrogenase but decreased the H₂-uptake hydrogenase activity.