Gas-phase reaction of benzo[a]anthracene with hydroxyl radical in the atmosphere: products, oxidation mechanism, and kinetics.

Polycyclic aromatic hydrocarbons (PAHs) have induced large-scale and long-term environmental contamination due to heavy emissions, toxicity, and persistence. The investigation of the ultimate sink of PAHs in the atmosphere is very important. In this work, using quantum chemistry methods, the reaction mechanism of hydroxyl radical-initiated oxidation of benzo[a]anthracene (BaA) in the atmosphere was studied. The products resulted from the gas-phase reaction of BaA with hydroxyl radical include benzo[a]anthracenols, dialdehydes, ketones, epoxides, etc. Applying Rice-Ramsperger-Kassel-Marcus (RRKM) theory, the overall rate constant for reactions of •OH addition to BaA was estimated to be 4.82 × 10-11  cm3 molecule-1  s-1 at 298 K and 1 atm. The lifetime of BaA in the atmosphere with respect to hydroxyl radical was calculated to be 5.92 h.