METABOLITE DETECTION AS EVIDENCE FOR NATURALLY-OCCURRING AEROBIC PCB BIODEGRADATION IN HUDSON RIVER SEDIMENTS

Although aerobic microbial biodegradation of polychlorinated biphenyls (PCBs) has been widely demonstrated in the laboratory, there is little direct evidence that this process occurs naturally in the environment. A clear indicator of naturally occurring aerobic PCB biodegradation would be the presence of intermediate metabolites such as chlorobenzoic acids (CBAs) in contaminated sediments. CBAs have been detected in contaminated sediment cores, and their concentration profiles were correlated with PCB depth profiles. From the congener distribution pattern of the CBAs detected, it is extremely unlikely that these compounds were derived from either the breakdown of chlorinated herbicides or the carboxylation of phenols. No CBAs were detected in sediment samples not contaminated with PCBs, In addition, other metabolites which are less prone to source ambiguity, including 2,3-dihydro-2,3-dihydroxy-2'-chlorobiphenyl and 2,3-dihydroxy-2'-chlorobiphenyl, have also been detected. To our knowledge, these findings represent the first detection of metabolites of aerobic PCB biodegradation in contaminated environmental samples.