PCB Congeners and Dechlorination in Sediments of Upper Sheboygan River, Wisconsin

Nine hand-collected sediment cores were obtained for PCB concentration analysis and dating from the Upper Sheboygan River, Wisconsin, USA. The primary PCB Aroclors in the Upper Sheboygan River were 1248 (50%) and 1254 (50%). The total PCB concentrations in the sediments ranged from 0.1-104 ppm (based on dry weight). The PCB data obtained from the sampling were analyzed using a factor analysis (FA) model with non-negative constraints in order to identify PCB sources and congener patterns. The factor loadings obtained from the FA model represent a general dechlorination profile common to most of the higher concentration samples and another associated with contamination from upstream dredging during 1989-1991. Anaerobic dechlorination is occurring in Upper Sheboygan River sediments and is most significant at high concentrations (≥ 20 ppm). Observation of elevated amounts of lower chlorinated congeners such as congeners 4 (2-2), 8 (2-4), 25 (24-3), and 26 (25-3) indicates the presence of anaerobic dechlorination activities. Based on the data from the FA model, anaerobic dechlorination was occurring according to dechlorination activities M and P. All possible dechlorination pathways involving marker congeners were considered. A significant improvement (86-91%) in similarity between the original Aroclor profile and the altered ones was found.