LOW-TEMPERATURE MICROBIAL AEROBIC DEGRADATION OF POLYCHLORINATED-BIPHENYLS IN SEDIMENT

To test for low-temperature microbial aerobic PCB degradation, water-s aturated samples of PCB-contaminated upper Hudson River sediment spike d with Aroclor 1242 were incubated at 4 degrees C for several months. Principal components analysis of the PCBs, quantified by GC-ECD and GC -MS, indicated the loss of specific congeners within the top 15 mm of sediment. In contrast, no loss of PCBs was observed in the deeper regi on (>15 mm from the surface) of the sediment or in any region of simil arly treated sediment samples that were autoclaved prior to Aroclor 12 42 addition. Loss of specific di-and trichlorobiphenyls typical of mic robial aerobic degradation was first indicated at 1.4 months, and >50% loss had occurred by 5 months. Initially, the sediment was dark brown , However, by 2 months a lighter, rust-colored layer developed at the top 6 mm that increased to similar to 10 mm by 5 months and to similar to 15 mm by 10 months. The color change, due at least in part to form ation of hydroxylamine-reducible ferric oxide, indicated the depth to which oxygen was available and the depth to which PCB degradation occu rred. In addition, chlorobenzoic acid metabolites of microbial aerobic PCB degradation were detected in the rust-colored layer. These observ ations demonstrate that low-temperature microbial aerobic PCB degradat ion can occur in PCB-contaminated sediment.