HR: 0800h
AN: A11A-0042    [Abstracts]
TI: Condensed Phase Organic Photochemistry in Atmospheric Aerosols
AU: * Van Wyngarden, A L
EM: avanwyngarden@arc.nasa.gov
AF: Atmospheric Science Branch NASA Ames Research Center, Mail Stop 245-5, Moffett Field, CA 94035, United States
AU: * Van Wyngarden, A L
EM: avanwyngarden@arc.nasa.gov
AF: NASA Postdoctoral Program, Oak Ridge Associated Universities, Oak Ridge, TN 37831- 0117, United States
AU: Iraci, L T
EM: Laura.T.Iraci@nasa.gov
AF: Atmospheric Science Branch NASA Ames Research Center, Mail Stop 245-5, Moffett Field, CA 94035, United States
AB: Many organic compounds that have been either observed or proposed to exist in atmospheric aerosols have significant UV-vis absorption cross-sections in the atmospheric window (< 290nm). Thus, photo-initiated reactions of these compounds may be important sinks for the particle-phase reactants as well as sources for new organic products in both the particle and gas phases. Currently, relatively little is known about the chemical fate of most organic compounds that absorb UV-visible radiation in the condensed phase, especially under the highly acidic conditions typical of sulfate aerosols in the upper troposphere and lower stratosphere. Here we present Attenuated Total Reflectance FTIR and UV-vis spectra that demonstrate chemical changes upon UV-vis irradiation of various organic compounds in sulfuric acid/water solutions under a range of acidities relevant for atmospheric aerosol particles and cloud droplets. For example, in aqueous methylglyoxal solution, the FTIR spectra show that UV-vis radiation alters the speciation of methylglyoxal among its various monomer (hydrated and dehydrated) and polymer forms. Concomitant changes in the preliminary UV-vis spectra confirm a changing distribution of carbonyl moieties and show that irradiation causes a decrease in absorption at atmospherically available wavelengths below 300 nm. These results are used to address the effects that particle-phase organic photochemistry may have on the optical properties and/or cloud processing of atmospheric aerosols.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0317 Chemical kinetic and photochemical properties
DE: 0320 Cloud physics and chemistry
DE: 0321 Cloud/radiation interaction
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting