Biodegradation of photoirradiated polycyclic aromatic hydrocarbon constituents of creosote oil

The influence of the photochemical pretreatment on the biodegradation of na phthalene, acenaphthene, fluorene, phenanthrene, anthracene, and pyrene wer e studied. In aqueous media these PAHs were photoreactive. Aerobic PAH degr ading bacteria were enriched on creosote or on a mixture of the six PAHs. T he pre-irradiation enhanced mainly the onset of the biodegradation, particu larly PAHs treated as the components of creosote. The biodegradation rate o f irradiated acenaphthene in creosote on the second day was 50% better than that in the non-irradiated sample. The biodegradation rates of anthracene irradiated individually and in creosote were 35% and 58% higher, respective ly, than those of the non-irradiated samples on the second day. On the seve nth day there was a 70% difference between the biodegradation rates of irra diated and non-irradiated pyrene treated in creosote in favor of the irradi ated sample. The biodegradation of non irradiated fluorene ceased in two da ys while the degradation of irradiated fluorene was almost complete in seve n days. Photochemical treatment produced several intermediates as detected by a gas chromatograph with a mass spectrometer (GC-MS). The intermediates were more biodegradable than the parent compounds.