PCB SOURCES, TRANSPORT AND FATE IN THE HUDSON RIVER: IMPLICATIONS FOR FUTURE ACTIONS

The Hudson River (New York) is massively contaminated with PCBs, resulting in the closure of important fisheries and risks to human and ecological health. As part of this study, new data gathering efforts were combined with historical ones in order to assess the impacts of contaminated sediments on human health and wildlife. The reassessment included a field investigation encompassing 200 river miles, applying state-of-the-art geochemical and analytical techniques to examine PCBs in the sediments, water and biota. The reassessment forms the basis for the recent proposal by the USEPA (December 2000) to dredge the most contaminated portions of the Upper Hudson. This proposal is based in part on the investigations conducted by TAMS Consultants, Inc. and its subcontractors for the USEPA. This presentation will describe several of these investigations and their implications for the USEPA's decision.Although the direct discharge ceased in 1977, PCBs have continued to leak into the Hudson from the GE sites to the present time. PCB use throughout New York increased over the period 1950–1970 as well, potentially yielding additional sources to the Hudson. A major question addressed during the reassessment was the importance of these other point and non-point sources. To accomplish this the USEPA used a congener-specific analytical technique, yielding concentrations for 140 individual congeners. Sediment cores were obtained throughout the Hudson, dated using radiocesium (Cs-137) and analyzed via this technique. Water-column samples were also analyzed on a congener-specific basis. These data permitted the “fingerprinting” of the PCB. Combining these data with statistical techniques, the results clearly identified the GE facilities as the original source of PCBs to the entire freshwater Hudson, representing over 150 miles of river, with the occurrence of a secondary source associated with the NYC harbor area. Historical deposition shows to this condition to be true over at least a 17 year period (1975–1992), although evidence for at least one other minor PCB release event during this period can be seen as well.The use of congener-specific analysis to examine PCB contamination in the environment yielded several other important results concerning PCB fate and transport. Although the PCB “fingerprints” identified the GE discharges as the original source of PCBs to the Hudson, the same techniques indicated that releases from the sediments are responsible for the majority of the on-going downstream transport of PCBs. This conclusion was based on a series of time-of-travel studies and PCB congener analyses that were able to clearly discern the sediment contribution. The use of sediment core dating and congener-specific analyses also clarified the issue of biodegradation in the sediments. Although dechlorination was evident in many samples, the extent of dechlorination was clearly limited, correlating with the level of PCB contamination and not the age of the sediments, as might be expected. In fact, no evidence for ortho-dechlorination was found, clearly limiting the importance of this process in reducing the PCB sediment inventory and associated health risks. The discussion will include the evidence supporting these major conclusions as well as their implications for the USEPA's recommended plan for the Hudson.