Kinetics of Surface-Bound Benzo[a]pyrene and Ozone on Solid Organic and Salt Aerosols

Abstract

An aerosol flow tube apparatus was developed to perform the first kinetic study of the oxidation of particulate-bound BaP on solid organic and salt aerosols by gas-phase ozone. The studies on azelaic acid aerosols were performed with submonolayer coatings of BaP under both dry (RH < 1%) and high relative humidity (RH ∼ 72%) conditions. The reaction exhibited pseudo-first-order kinetics for BaP loss and the pseudo-first-order rate coefficients displayed a Langmuir−Hinshelwood dependence on gas-phase ozone concentration. Under high relative humidity conditions the kinetics were faster but also displayed a similar functional dependence on the gas-phase ozone concentration. By assuming Langmuir−Hinshelwood behavior, the following parameters were obtained: ozone-surface equilibrium constant KO3(< 1% RH) = (1.2 ± 0.4) × 10-15 cm-3, KO3(72% RH) = (2.8 ± 1.4) × 10-15 cm-3, the maximum pseudo-first-order rate coefficient (< 1% RH) = (0.048 ± 0.008) s-1, (72% RH) = (0.060 ± 0.018) s-1. Uptake coefficients were ext...