HR: 0800h
AN: A11B-0046    [Abstracts]
TI: Quantum Yields for OH Formation from the Photolysis of Nitrite on Ice: Comparison to Nitrate and Hydrogen Peroxide
AU: * Chu, L
EM: lchu@ucdavis.edu
AF: University of California, Davis, Department of Land, Air, and Water Resources, One shields Avenue, Davis, CA 95616 United States
AU: Anastasio, C
EM: canastasio@ucdavis.edu
AF: University of California, Davis, Department of Land, Air, and Water Resources, One shields Avenue, Davis, CA 95616 United States
AB: The photodecomposition of nitrate, nitrite, and hydrogen peroxide generates hydroxyl radicals (OH) in ice and snow. These photoreactive species can affect snow chemistry as well as ice-core records and the atmospheric boundary layer. For example, it has been hypothesized that photoformed OH can oxidize organic carbon in the snowpack and lead to the release of volatile organic compounds such as formaldehyde. While the quantum yields of OH radicals from the photolysis of nitrate and hydrogen peroxide in ice have been measured,[1-3] the photochemical behavior of nitrite in ice and snow remains an open issue. In this study, we are measuring the quantum yields of the OH radical ($\Phi$(NO$_{2}^{-} \longrightarrow$ OH)) from the photolysis of frozen aqueous NO$_{2}^{-}$ solutions using benzoate as a chemical probe. For this presentation we will discuss: (1) NO$_{2}^{-}$ molar absorptivities; (2) The temperature dependence of ($\Phi$(NO$_{2}^{-} \longrightarrow$ OH)) for ice pellets at temperatures between 243 K and 268 K, and (3) The pH dependence of ($\Phi$(NO$_{2}^{-} \longrightarrow$ OH)) and the relative reactivities of NO$_{2}^{-}$ and HNO$_{2}$ at 263 K. We will also compare the nitrite results with those previously determined for nitrate and hydrogen peroxide, including the relative contributions for OH formation from nitrate, nitrite, and hydrogen peroxide in the snow, and the atmospheric implications of these reactions. References: 1. Dubowski, Y.; Colussi, A. J.; Hoffmann, M. R. J.Phys.Chem.A 2001, 105, 4928. 2. Chu, L.; Anastasio, C. J.Phys.Chem.A 2003, 107, 9594. 3. Chu, L.; Anastasio, C. Quantum Yields of OH from the Photolysis of Hydrogen Peroxide in Ice, in preparation.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0317 Chemical kinetic and photochemical properties
DE: 0325 Evolution of the atmosphere
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting