The fate of radiolabeled ([C-14]) phenanthrene, pyrene, benz[a]anthracene, chrysene, and benzo[a]pyrene was examined in five soils, four of which had previous exposure to polycyclic aromatic hydrocarbons (PAHs), The soils and [C-14]PAHs studied represent a range of characteristics (fraction of soil organic carbon [f(oc)] and PAH solubility) that can potentially impact contaminant fate. Fates of [C-14]PAHs examined in slurry microcosms included mineralization, production of water-soluble metabolites and their polarity, cellular incorporation, and the association of [C-14]PAHs with soils, all compared to an abiotic control. The soils all contained active heterotrophic communities and the contaminated soils had sizable populations of PAH-degrading microorganisms, measured by the [C-14]-most probable number assay. All [C-14]PAHs, except [C-14]benzo[a]pyrene, were readily mineralized in most of the preexposed soils, whereas in the uncontaminated soil, less than 5% of each [C-14]PAH was mineralized, in the adapted soils, mineralization, after 8 weeks of incubation, accounted for 30 to 60% of [C-14]phenanthrene, 10 to 55% of [C-14]pyrene, 5 to 40% of [C-14]benz[a]anthracene, 10 to 50% of [C-14]chrysene, and 2 to 9% of [C-14]benzo[a]pyrene added to the microcosms. Metabolite production and cellular incorporation usually accounted for less than 10% of the added [C-14]PAH, The fare of PAHs was usually not related to measurements of microbial community size, characteristics of the PAH (water solubility and K-ow), and many characteristics of soils (soil f(oc) and PAH concentration). The fraction of silt and clay in the soils for each soil-PAH combination, however, was negatively related to the extent of added [C-14]PAH mineralized and the amount solvent extractable from the soil, and positively related to the amount of [C-14]PAH remaining in soils after extraction.
