AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
A Comparison of the Chemical Sinks of Atmospheric Organics in the Gas and Aqueous Phase
SCOTT A. EPSTEIN, Sergey Nizkorodov, University of California, Irvine
Abstract Number: 398 Working Group: Aerosol Chemistry
Abstract It is now recognized that aqueous-phase reactions in the atmosphere can contribute to the production and/or aging of organic aerosols. However, the role of direct vs. indirect aqueous photochemical processes is currently uncertain. To better understand the significance of different gas-phase and aqueous-phase photochemical processes in transforming atmospheric volatile organic compounds (VOCs), we estimate the relative rates for oxidation by hydroxyl radical (OH) and of direct photolysis by actinic radiation in the gas phase and of VOCs dissolved in cloud droplets. We constrain these rates with published rate constants that are well established in the literature. However, the atmospheric significance of direct aqueous photolysis is uncertain due to the lack of absorption cross sections and photolysis quantum yields measured in the aqueous phase. Our relative rate approach allows us to examine the importance of aqueous photolysis for the compounds investigated in spite of the limited published data. We determine the relative magnitudes of these four photochemical sinks for 27 atmospherically relevant species inside air parcels containing cloud and fog droplets. Results of this analysis will help guide researchers by identifying compounds that are likely to be destroyed by photolysis inside cloud or fog droplets, and lead to the generation or aging of organic aerosols.