HR: 0800h
AN: A51D-0738    [Abstracts]
TI: Heterogeneous Photochemical Oxidation of Sulfur Dioxide
AU: El-Zanan, H S
EM: hazem@dri.edu
AF: Desert Research Institute, 2215 Raggio pkwy, reno, nv 89512,
AU: * Stockwell, W R
EM: wstockwell@howard.edu
AF: Howard University, Department of Chemistry, Room 120 525 College Street, NW, washington, DC 20059,
AB: The gas phase oxidation of sulfur dioxide by the hydroxyl radical is a significant source of sulfate aerosol in the troposphere and stratosphere. Stockwell and Calvert (1983) performed fifteen chamber experiments where mixtures of HONO, NO, NO2, H2O, SO2 and CO were photolyzed in synthetic air or in nitrogen containing approximately 50 ppm oxygen. They found that the atmospheric oxidation of SO2 by hydroxyl radical was a chain process that occurs through the production of an HO2 radical followed by reaction with NO to reproduce HO. We have reanalyzed this dataset and we have found that a very large amount of the observed SO2 oxidation (70.0 ± 9.1 %) is not explained through the HO + SO2 reaction alone. The Regional Atmospheric Chemistry Mechanism (RACM2) was used to investigate additional chemical pathways for the oxidation of SO2. A mechanism consisting of photochemical heterogeneous reactions is proposed to account for the observed additional sulfur dioxide oxidation not accounted for by gas phase oxidation. The analysis showed that the measured time dependent SO2, CO2 and nitrogenous compound concentrations could be simulated by the photochemical heterogeneous mechanism in conjunction with the RACM2 mechanism.
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1622 Earth system modeling (1225)
DE: 4801 Aerosols (0305, 4906)
DE: 4906 Aerosols (0305, 4801)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting