Photostability of polycyclic aromatic hydrocarbons (PAHs) and nitrated polycyclic aromatic hydrocarbons (NPAHs) in dichloromethane and isooctane solutions

Kinetics of photodegradation of eight PAHs (naphthalene, anthracene, phenanthrene, 1) pyrene, biphenyl, chrysene, benz[a]anthracene and tetracene) and five NPAHs (1-nitronaphthalene, 2-nitrofluorene, 9-nitroanthracene, 1-nitropyrene and 6-nitrochrysene) was studied in isooctane and dichloromethane solutions standing in a laboratory and in a light simulator. Samples were stored in closed glass vials and fused silica cuvettes. PAHs and NPAHs were divided into three groups according to their life times. Degradation, of all PAHs and NPAHs was faster in dichloromethane compared with isooctane. Decomposition of NPAHs was easier than degradation of corresponding parent PAHs. The most frequent photoproducts were quinones, benzoic acid and other derivatives with hydroxyl, carbonyl and carboxyl groups for both PAHs and NPAHs. Chlorinated compounds were identified in dichloromethane. Degradation intermediates underwent further oxidation, fragmentation, reduction or radical chlorine addition in dichloromethane. Final degradation products of all PAHs were n-alkanes. Based on GC-MS data the mechanism of photoproducts formation was proposed.