Radiolabeled polycyclic aromatic hydrocarbons (PAH) containing up to three rings, including naphthalene, methylnaphthalenes, and phenanthrene, were degraded (measured by 14CO2 production) in water samples from both Narragansett Bay and southeastern United States. Higher weight PAH, including benz[a]anthracene, chrysene, fluorene, and anthracene, showed little, if any, degradation in water but were readily degraded when added to sediment–water slurries. In areas with low levels of petroleum in the water or sediment there was a lag before appreciable degradation began, and the rate of degradation fitted a first-order equation. Half-lives, calculated for the various PAH added to water or sediment–water slurries, were very low during winter months; [14C]methylnaphthalene added to water from Skidaway River, Georgia, in January (8 °C) was 57 d, while in September (28 °C) it was 3 d. PAH added to sediments or water from oil-treated areas or mesocosms were rapidly degraded with no lag phase and the degradation rate was linear. [14C]Methylnaphthalene added to water from control and oiled mesocosms in May (10 °C) had half-lives of 300 and 5 d, respectively. We plotted the changes in turnover times with changes in the concentration of PAH and calculated the natural turnover times and Vmax for PAH added to water or sediment from the oiled mesocosms. When [14C]dimethylbenz[a]anthracene was incubated in water in the dark no degradation occurred, but when exposed to sunlight, 0.3% was mineralized in 18 h. In addition, a variety of photooxidation products were produced. The production of 14CO2 in the light was due to microbial degradation of photooxidation products of [14C]dimethylbenz[a]anthracene.
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Richard F. Lee (1983) studied this question.