AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Trends in the Oxidation and Relative Volatility of Chamber-Generated Secondary Organic Aerosols
KENNETH DOCHERTY, Eric Corse, Mohammed Jaoui, John Offenberg, Tad Kleindienst, Jonathan Krug, Theran Riedel, Michael Lewandowski, EPA/ORD/NERL
Abstract Number: 737 Working Group: Aerosol Chemistry
Abstract The relationship between the oxidation and relative volatility of chamber-generated secondary organic aerosol (SOA) generated from reaction of a number of different hydrocarbons is investigated using a fast-stepping, scanning thermodenuder (TD) interfaced with a high resolution time-of-flight aerosol mass spectrometer (AMS). With respect to a particular parent hydrocarbon, SOA oxidation obtained from replicate experiments is relatively stable and unit-resolution (UR) indicators (f43, f44) are consistent with literature values. Oxidation, however, is highly variable of among different parent hydrocarbons based on both UR indicators and ratios obtained from elemental analysis (EA) of high-resolution spectra. Linear regression of H:C vs O:C obtained both from parameterization of f43 and f44 and from EA in Van Krevelen space suggest that oxidation across different SOA types occurs via carboxylation with subsequent fragmentation consistent with recent analyses. Similar regression of ratios obtained from a subset of toluene photooxidation reactions with different integrated OH exposures provides similar results. Relative volatility shows the same trends, being fairly stable within reactions of a particular hydrocarbon or hydrocarbon class but exhibiting a large degree of variability among different hydrocarbons. Across the wide range of SOA types investigated relative volatility of both SOA and total chamber aerosol is proportional to and highly correlated with carbon oxidation state (OSc).