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

Abstract

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 2.35×10−12cm3 molecule−1s−1 at 298K and 1atm. The atmospheric lifetime of 9,10-Cl2Phe determined by OH radicals is about 5.05days. This study provides a comprehensive investigation of the OH-initiated oxidation degradation of 9,10-Cl2Phe and should contribute to clarifying its atmospheric fate.