Mechanism and kinetic properties for the OH-initiated atmospheric oxidation degradation of 9,10-Dichlorophenanthrene

Chlorinated polycyclic aromatic hydrocarbons (ClPAHs) have become a serious environmental concern due to their widespread occurrence and dioxin-like toxicities. In this work, the mechanism of the OH-initiated atmospheric oxidation degradation of 9,10-dichlorophenanthrene (9,10-Cl2Phe) was investigated by using high-accuracy quantum chemistry calculations. The rate constants of the crucial elementary reactions were determined by the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The theoretical results were compared with the available experimental data. The main oxidation products are a group of ring-retaining and ring-opening compounds including chlorophenanthrols, 9,10-dichlorophenanthrene-3,4-dione, dialdehydes, chlorophenanthrenequinones, nitro-9,10-Cl2Phe and epoxides et al. The overall rate constant of the OH addition reaction is 2.35 × 10− 12 cm3 molecule− 1 s− 1 at 298 K and 1 atm. The atmospheric lifetime of 9,10-Cl2Phe determined by OH radicals is about 5.05 days. This study provides a comprehensive investigation of the OH-initiated oxidation degradation of 9,10-Cl2Phe and should contribute to clarifying its atmospheric fate.