Atmospheric degradation of chrysene initiated by OH radical: A quantum chemical investigation

Chrysene, a four-ring polycyclic aromatic hydrocarbon (PAH), is recalcitrant to biodegradation and persistent in the environment due to its low water solubility. Here, we investigated the atmospheric degradation process of chrysene initiated by OH radical in the presence of O-2 and NOX using quantum chemical calculations. The reaction mechanisms were elucidated by density functional theory (DFT) at M06-2X/6-311++G(3df,2p)//M06-2X/6-311+G(d,p) level, and the kinetics calculations were conducted with Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The results show that the oxidation products of atmospheric chrysene are oxygenated PAHs (OPAHs) and nitro-PAHs (NPAHs), including nitro-chrysene, hydroxychrysene, hydroxychrysenone, 11-benzo[a]fluorenone and dialdehydes. Most of the products have deleterious effects on the environment and human beings due to their acute toxicity, carcinogenicity and mutagenicity. The overall rate constant for the reaction of chrysene with OH radical is 4.48 x 10(-11) cm(3) molecule(-1) s(-1) and the atmospheric lifetime of chrysene determined by OH radical is 6.4 h. The present work provided a comprehensive understanding on the degradation mechanisms and kinetics of chrysene, which could help to clarify its atmospheric fate and environmental risks. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Chrysene, a recalcitrant polycyclic aromatic hydrocarbon, undergoes atmospheric degradation initiated by OH radical, generating toxic oxygenated and nitro products. The study reveals the rate constant and atmospheric lifetime of chrysene in reaction with OH radical.