HR: 0800h
AN: A51C-0086    [Abstracts]
TI: Kinetics of the Heterogeneous Reactions of Ozone with Several PAHs on Organic Films
AU: * Kahan, T
EM: tkahan@chem.utoronto.ca
AF: Department of Chemistry University of Toronto, 80 St. George St., Toronto, ON M5S 3H6 Canada
AU: Donaldson, J
EM: jdonalds@chem.utoronto.ca
AF: Department of Chemistry University of Toronto, 80 St. George St., Toronto, ON M5S 3H6 Canada
AB: Urban surfaces are covered with a surface film of complex composition. The partitioning of atmospheric organic compounds to such films, and their subsequent reactions, are believed to be governed by the film organic content. We report experiments in which six PAHs were sorbed onto mixed organic substrates that attempt to simulate this film; the kinetics of their reactions with gas phase ozone were determined by measuring the PAH loss rates using laser-induced fluorescence. For all compounds studied, the dependence of the pseudo-first order rate coefficient on the gas phase ozone concentration was well described by a Langmuir-Hinshelwood surface mechanism. At an ozone mixing ratio of 50 ppb, the lifetimes against loss by heterogeneous reaction with ozone range from about four days to several years. Further experiments were conducted to determine the role of the substrate composition on the reaction rate. The presence of carbohydrates, silicone grease, hydrocarbon-based vacuum grease, and saturated organic acids and alcohols of various chain lengths did not affect the reaction rates. The presence of alkenes significantly reduced the rate of reaction. The reactions of ozone with some PAHs on surface films may be of comparable importance to the reactions of these PAHs with the hydroxyl radical in the atmosphere.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 3304 Atmospheric electricity
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005