Microbial and Photochemical Degradation of Polycyclic Aromatic Hydrocarbons in Estuarine Waters and Sediments

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 ra...