Web Release Date: June 30,
Measurements of Secondary Organic Aerosol from Oxidation of Cycloalkenes, Terpenes, and m-Xylene Using an Aerodyne Aerosol Mass Spectrometer
and
Department of Environmental Science and Engineering, and Department of Chemical Engineering, California Institute of Technology, Mail Code 210-41, 1200 East California Boulevard, Pasadena, California 91125, Aerodyne Research, Inc., 45 Manning Road, Billerica, Massachusetts 01821, and Department of Chemistry & Biochemistry and CIRES, University of Colorado-Boulder, UCB 216, Boulder, Colorado 80309
Received for review December 7, 2004
Revised manuscript received April 27, 2005
Accepted May 19, 2005
Abstract:
The Aerodyne aerosol mass spectrometer (AMS) was
used to characterize physical and chemical properties of
secondary organic aerosol (SOA) formed during ozonolysis
of cycloalkenes and biogenic hydrocarbons and photooxidation of m-xylene. Comparison of mass and volume
distributions from the AMS and differential mobility analyzers
yielded estimates of "effective" density of the SOA in
the range of 0.64-1.45 g/cm3, depending on the particular
system. Increased contribution of the fragment at m/z
44, CO2+ ion fragment of oxygenated organics, and higher
"
" values, based on ion series analysis of the mass
spectra, in nucleation experiments of cycloalkenes suggest
greater contribution of more oxygenated molecules to
the SOA as compared to those formed under seeded
experiments. Dominant negative "" values of SOA formed
during ozonolysis of biogenics indicates the presence of
terpene derivative structures or cyclic or unsaturated
oxygenated compounds in the SOA. Evidence of acid-catalyzed heterogeneous chemistry, characterized by greater
contribution of higher molecular weight fragments to the
SOA and corresponding changes in "" patterns, is observed
in the ozonolysis of 
-pinene. Mass spectra of SOA
formed during photooxidation of m-xylene exhibit features
consistent with the presence of furandione compounds
and nitro organics. This study demonstrates that mixtures
of SOA compounds produced from similar precursors
result in broadly similar AMS mass spectra. Thus,
fragmentation patterns observed for biogenic versus
anthropogenic SOA may be useful in determining the
sources of ambient SOA.
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