HR: 0800h
AN: A21A-0833    [Abstracts]
TI: The Chemistry of Mixed Sodium Chloride and Sodium Nitrate Aerosol Particles: Impacts of a Secondary Inorganic Ion on Gas Phase Chlorine Production
AU: Wingen, L M
EM: wingenit@uci.edu
AF: University of California, Irvine, Department of Chemistry, Irvine, CA 92697-2025 United States
AU: * Moskun, A C
EM: amoskun@uci.edu
AF: University of California, Irvine, Department of Chemistry, Irvine, CA 92697-2025 United States
AU: Thomas, J L
EM: jenniet@uci.edu
AF: University of California, Irvine, Department of Chemistry, Irvine, CA 92697-2025 United States
AU: Roeselova, M
EM: martina.roeselova@uochb.cas.cz
AF: Institute of Organic Chemistry and Biochemistry and Center for Complex Molecular Systems and Biomolecules, Academy of Sciences of the Czech Republic, Prague, 166 10 Czech Republic
AU: Tobias, D J
EM: dtobias@uci.edu
AF: University of California, Irvine, Department of Chemistry, Irvine, CA 92697-2025 United States
AU: Finlayson-Pitts, B J
EM: bjfinlay@uci.edu
AF: University of California, Irvine, Department of Chemistry, Irvine, CA 92697-2025 United States
AB: Unique chemistry at the air-water interface from the reaction of the chloride ion and the hydroxyl radical has been suggested to play a major role in the production of increased levels of molecular chlorine in the marine boundary layer, including coastal regions. Molecular chlorine can then be photolyzed by solar radiation to produce the highly reactive atomic chlorine radical. Laboratory studies have shown that an interfacial reaction between chloride ion and the hydroxyl radical is responsible for generation of molecular chlorine at concentrations which cannot be explained by well-known bulk aqueous chemistry. Molecular dynamics (MD) simulations of chloride ion solutions as well as sum frequency generation studies have shown that the chloride ion has a propensity for the air-water interface. We examine here how the addition of nitrate ion to the aerosol, which is also believed to have a significant interfacial concentration in pure nitrate particles, affects the production of molecular chlorine. Laboratory experiments using mixed NaCl/NaNO₃ aerosol particles were performed in a 561 L aerosol chamber at 298 K, 1 atm, and ~85% relative humidity, above the deliquescence points for both salts. Aerosol particles were generated using a commercial atomizer and Cl₂ production was measured using atmospheric pressure chemical-ionization mass spectrometry; long path FTIR and DOAS were also used for monitoring ozone and the formation of reaction products. Ozone photolysis at 254 nm was used as a hydroxyl radical source. Molecular chlorine formation is observed from the reaction of the mixed NaCl/NaNO₃ aerosol with OH, suggesting that at least some of the chloride remains at the interface in the mixed NaCl/NaNO₃ particles. The results of chamber experiments with varying aerosol composition and size will be presented and interpreted in the context of molecular dynamics simulations of pure chloride, pure nitrate and mixed composition aerosol. The implications of this work for the production of reactive chlorine atoms in the troposphere will be discussed.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005