Photodegradation products of polycyclic aromatic hydrocarbons in water and their amenability to biodegradation

Saturated water solutions of anthracene, pyrene, benz[a]anthracene, and dibenz[a,h]anthracene were UV-irradiated in the presence of oxygen and their photodegradation products were identified. The products were then individually photolyzed. Several products of photolysis were identified chromatographically. Furthermore, the biodegradation of two photoproducts, 9,10-anthracenedione and benz[a]anthracene-7,12-dione, was studied separately and in the presence of the original polycyclic aromatic hydrocarbons (PAHs). The irradiation of anthracene first produced 9,10-anthracenedione and continuous illumination yielded additionally 1-hydroxy-9,10-anthracenedione, 1,4-dihydroxy-9,10-anthracenedione, 9-anthrone, and 1(3H)-isobenzofuranone. Photolysis of benz[a]anthracene produced benz[a]anthracene-7,12-dione and 1(3H)-isobenzofuranone. By irradiation of pyrene and dibenz[a,h]anthracene mainly diones of the original compounds were formed. In batch vial experiments, the biodegradation of 9,10-anthracenedione alone started with no lag phase whereas biodegradation of anthracene alone had a lag of 40 days. The lag for benz[a]anthracene biodegradation was, in the presence and absence of benz[a]anthracene-7,12-dione, 17 and 35 days, respectively.