Behavior and prediction of photochemical degradation of chlorinated polycyclic aromatic hydrocarbons in cyclohexane

The photochemical degradation of I I chlorinated polycyclic aromatic hydrocarbons (CIPAHs) and the corresponding 5 parent PAHs was examined to simulate the compound's fate on aerosol surfaces. All the CIPAHs and PAHs decayed according to the first-order reaction rate kinetics. The photolysis rates of CIPAHs varied greatly according to the skeleton of PAHs; the rates of chlorophenanthrenes (ClPhes) and 1-chloropyrene were higher than those of corresponding parent PAHs, whereas chlorofluoranthenes, 7-chlorobenz[a]anthracene and 6-chlorobenzo[a]pyrene were more stable under irradiation compared to respective parent PAH. Considering the photoproducts of ClPhes detected, the oxidation could occur immediately at positions of the highest frontier electron density. Finally, the quantitative structure-property relationship models were developed for direct photolysis half-lives and average quantum yields of the CIPAHs and parent PAHs, in which the significant factors affecting photolysis were ELUMO+1, total energy and surface area, and E-LUMO, E-LUMO-E-HOMO and total energy, respectively. (c) 2007 Elsevier Ltd. All rights reserved.