Abstract:
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.
