Remediation at a Marine Superfund Site: Surficial Sediment PCB Congener Concentration, Composition, and Redistribution

New Bedford Harbor (NBH) is an estuary severely contaminated with polychlorinated biphenyls (PCBs) and is undergoing a multistage Superfund remediation. A long-term monitoring program was developed to assess the effectiveness of this remediation. Seventy-two stations were monitored in the harbor and in adjacent Buzzards Bay. Sediments were collected at each station before and after the initial remedial phase (the “hot spot” removal), and the concentrations of 18 PCB congeners were quantified. A qualitative graphical technique was combined with exploratory statistical techniques to examine the spatial and temporal variability in concentrations of PCBs and proportions of the congeners. The combination of the two techniques with PCB congener ratios revealed subtle changes after remediation that were not evident by a more traditional statistical analysis of total PCB concentrations. Although major redistributions of contaminated sediments were confined to the immediate vicinity of remedial activities, there is evidence that low molecular weight PCBs were transported farther.