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This experimental study deals with heterogeneous reactions of benzo(a)pyrene (BaP) with ozone, nitrogen dioxide and hydroxyl radicals. BaP was adsorbed on silica particles chosen here as a model of mineral atmospheric particles. Compound extractions were assisted by focused microwave and analyses were performed by gas chromatography coupled with mass spectroscopy in single ion monitoring mode. Pseudo-first order rate constants were obtained from the fit of experimental decays of particulate-BaP concentration versus reaction time. Second order rate constants were determined considering the different oxidant gaseous concentrations except for the case of hydroxyl radicals where only a pseudo-first order rate constant was proposed. Values obtained at room temperature are (2.1±0.5)×10 −15  cm 3  molecule −1  s −1  for (BaP + ozone), (5.8±1.4)×10 −16  cm 3  molecule −1  s −1  for (BaP + nitrogen dioxide) and (3.4±0.8)×10 −2  s −1  for (BaP + OH) reactions. Products have only been investigated for the NO 2  and the OH (in the presence of NO x ) reactions. 1-, 3- and 6-nitrobenzo(a)pyrenes were detected as degradation products and quantified. Reaction rate constants for product formation are (3.7±0.9)×10 −16  cm 3  molecule −1  s −1  for 6-NBaP, (2.2±0.6)×10 −17  cm 3  molecule −1  s −1  for 1-NBaP and (5.3±1.3)×10 −17  cm 3  molecule −1  s −1  for 3-NBaP. 1-, 3- and 6-nitroBaP account respectively for approximately 5%, 12% and 83% of total nitrated species. If in the presence of only nitrogen dioxide, BaP was totally degraded within few minutes, only 20 to 25 % of the initial BaP led to nitrated compounds when reacting with OH (in the presence of NO x ).

Atmospheric Heterogeneous Reactions of Benzo(a)pyrene