Identification, Quantification and Distribution of Polychlorinated Biphenyls (PCBs) in Sediments of the Rappahannock and York River Watersheds




Cooper, Budoin-Brutus

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This study is intended to contribute to an understanding of water quality in a portion of the Chesapeake Bay: the Rappahannock and York watersheds. My PhD dissertation research is to identify, quantify, and determine the distribution of polychlorinated biphenyls (PCBs) in river sediments. These watersheds are adjacent to each other and are sub-watersheds of the Chesapeake Bay watershed (VA DCR, 1993). PCBs are a group of man-made chemicals. The basic chemical structure of PCBs consists of two-ring aromatic hydrocarbon biphenyls (Manahan, 1994). By substituting 1 to 10 chlorine atoms at specific positions on the aromatic biphenyls, over 200 different compounds can be produced. In general, PCBs are chemically and thermally stable. It is hypothesized that PCB-contaminated sediments in some parts of both the Rappahannock and York watersheds are excessive and that there is a need for remediation. Identification of “PCB hot spots” is a necessary procedure prior to a determination as to whether or not remediation of PCB-contaminated sediment is warranted. Remediation of PCB-contaminated sediment from a river system can improve water quality. The objective of this dissertation is to determine if any parts of York and Rappahannock watersheds need remediation. This study proposes to determine if significant concentrations of PCB contaminants exist, and if so, to determine the extent of contamination. This study designed and used a systematic grid sampling method. Systematic sampling was used to collect statistically representative sediment samples from the York and Rappahannock River watersheds. United States Environmental Protection Agency (U.S. EPA) method 1668A was used to chemically analyze each sediment sample for PCB homologues and total PCBs. Nonparametric statistical methods and personal computers were used to statistically analyze concentrations of PCBs in sediment samples. Results from chemical analyses of sediment samples from both the Rappahannock and York watersheds detected maximum total PCBs concentrations of 1170 pg/g for the lower York Watershed, 2279.6 pg/g for Lake Anna subwatershed, and 3120 pg/g for the Rappahannock watershed. The TSCA action level of 50 mg/kg is equivalent to 50,000 pg/g. The Maximum total PCBs detected in sediment samples from both watersheds are far less than TSCA definition of PCB waste materials. It is therefore concluded that no significant concentrations of total PCBs were found in the York River watershed nor the Rappahannock River watershed.



Polychlorinated biphenyls, Lake Anna, York River, Water quality, Rappahannock River, Chesapeake Bay