Estimation of Freely-Dissolved Concentrations of Polychlorinated Biphenyls, 2,3,7,8-Substituted Congeners and Homologs of Polychlorinated dibenzo-p-dioxins and Dibenzofurans in Water for Development of Total Maximum Daily Loadings for the Bluestone River Watershed, Virginia and West Virginia

Abstract

The Commonwealth of Virginia Department of Environmental Quality, working closely with the State of West Virginia Department of Environmental Protection and the U.S. Environmental Protection Agency is undertaking a polychlorinated biphenyl source assessment study for the Bluestone River watershed. The study area extends from the Bluefield area of Virginia and West Virginia, targets the Bluestone River and tributaries suspected of contributing to polychlorinated biphenyl, polychlorinated dibenzo-p-dioxin and dibenzofuran contamination, and includes sites near confluences of Big Branch, Brush Fork, and Beaver Pond Creek. The objectives of this study were to gather information about the concentrations, patterns, and distribution of these contaminants at specific study sites to expand current knowledge about polychlorinated biphenyl impacts and to identify potential new sources of contamination. Semipermeable membrane devices were used to integratively accumulate the dissolved fraction of the contaminants at each site. Performance reference compounds were added prior to deployment and used to determine site-specific sampling rates, enabling estimations of time-weighted average water concentrations during the deployed period. Minimum estimated concentrations of polychlorinated biphenyl congeners in water were about 1 picogram per liter per congener, and total concentrations at study sites ranged from 130 to 18,000 picograms per liter. The lowest concentration was 130 picograms per liter, about threefold greater than total hypothetical concentrations from background levels in field blanks. Polychlorinated biphenyl concentrations in water fell into three groups of sites: low (130-350 picogram per liter); medium (640-3,500 picogram per liter; and high (11,000-18,000 picogram per liter). Concentrations at the high sites, Beacon Cave and Beaverpond Branch at the Resurgence, were about four- to sixfold higher than concentrations estimated for the medium group of sites. Minimum estimated concentrations of polychlorinated dibenzo-p-dioxin and dibenzofuran congeners in water were about 0.2 to 1 femtograms per liter. Estimated total concentrations of 2,3,7,8-substituted congeners in water at study sites ranged from less than 1 to 22,000 femtograms per liter and less than 1 to 2,300 femtograms per liter for polychlorinated dibenzo-p-dioxin and dibenzofuran congeners, respectively. Total concentrations of 2,3,7,8-substituted congeners in water were comprised largely of octachlorodibenzo-p-dioxin and dibenzofuran, with less than 10 percent of the total contributed by concentrations of other congeners, mainly 2,3,7,8-heptachlorodibenzo-p-dioxin and dibenzofuran. Of special interest for this study was 2,3,7,8-tetrachlorodibenzo-p-dioxin with a regulatory surface water-quality criterion of 1,200 femtograms per liter. Estimated concentrations in water ranged from 0.5 to 41 femtograms per liter. Concentrations in water were less than 5 femtograms per liter at all study sites, except the Bluefield Westside Sewage Treatment Plan, with an estimated concentration of 41 femtograms per liter. Estimated total concentrations of homologs of polychlorinated dibenzo-p-dioxins and dibenzofurans in water at the study sites ranged from 3,200 to 36,000 femtograms per liter and 210-4,800 femtograms per liter, respectively. Again, homologs of polychlorinated dibenzo-p-dioxins and dibenzofurans in water were comprised largely of octachlorodibenzo-p-dioxin and dibenzofuran.