Study Of Phototransformation Of Benzo[a]pyrene In High Salinity Aqueous Solution

Polycyclic aromatic hydrocarbons(PAHs) are an important category of pollutants in aquatic environment and have teratogenicity, mutagenicity and carcinogenicity. Benzo[a]pyrene(Ba P) is a typical high molecular weight PAHs with strong hydrophobicity and high toxicity, was chosen as the model species in the work. Natural water is rich in a class of photosensitive substance, which may promote free radicals with high activity and low selectivity upon absorption of solar energy, positive metal ions, negative ions, and humus, for instance. The goal of this work is to give a primary knowledge of the special phototransformational characteristics of the polycyclic aromatic hydrocarbons compounds. We mainly studied the photochemistry transformation of Ba P in aqueous solution in the presence of Cl- and NO2-/Fe3+. The major results obtained from the experiments are as follows.(1) The photodegradation and phototransformation of Ba P was investigated in the Cl--containing solution experiments. Chloride ions can promote benzo[a]pyrene photodegradation and chloro-derivative―6-chlorobenzo[a]pyrene photogeneration. The triplet states 3Ba P* react with O2 in a complex formed by energy transfer from 3Ba P* to O2 and Cl- combinding with the complex to generate 6-chlorobenzo[a]pyrene. Results show that photochlorination of Ba P in seawater could occur, which suggest a natural source of chlorinated products in the environment.(2) The phototransformation of Ba P was investigated in the NO2-/Fe3+-containing solution experiments. The nitro-derivatives―1-NO2 Ba P, 3-NO2 Ba P and 6-NO2 Ba P were generated. The radicals ?NO2 and ?OH which play an important role in the nitro-substitute of Ba P process and Fe3+ promote to generate ?OH.