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NATURAL RECOVERY OF PCB - CONTAMINATED SEDIMENTS IN A FRESH WATER LAKE
Citation:
Brenner*, R C., V. S. Magar, J. A. Ickes, Foote, Eastep, L. S. Bingler, E. A. Crecelius, AND PevenMcCarthy. NATURAL RECOVERY OF PCB - CONTAMINATED SEDIMENTS IN A FRESH WATER LAKE. Presented at Second International Conference on Remediation of Contaminated, Venice, Italy, 09/30 - 10/03/2003.
Description:
Abstract: An ongoing study of natural recovery of sediments contaminated with polychlorinated biphenyls (PCBs), sponsored by the U.S. Environmental Protection Agency (EPA), is being pursued at the Sangamo-Weston/Twelvemile Creek/Lake Hartwell Superfund Site (i.e., the Lake Hartwell Site) near Clemson, South Carolina (USA). Approximately 400,000 lb (180,000 kg) of PCBs resulting from capacitor manufacturing at the Sangamo-Weston plant were discharged into Lake Hartwell and its Twelvemile Creek tributary between 1955 and 1978. Capacitor manufacturing operations ceased in 1978, and the terrestrial source of continuing PCB contamination was removed from the plant site in the early- to mid-1990s.
Natural recovery was selected in 1994 by U.S. EPA Region 4 as the remedy-of-choice to restore the Lake Hartwell ecosystem. The rationale for selecting natural recovery was that over time deposition of clean sediment would cover and effectively bury the contaminated sediment, thereby forming a barrier preventing further diffusion and migration of PCBs from the sediment into the benthos and water column. The target concentration established by Region 4 for the surface sediments (top 10 cm) was 1.0 mg/kg total PCBs.
Sediment samples were collected in 2000 and 2001 using deep coring techniues (core depths of 30 - 170 cm). In 2000, cores were sampled along the centerline of 10 transects (four in Twelvemile Creek and six in Lake Hartwell) preselected by Region 4. In 2001, cores were taken across (bank to bank) three of the six transects in Lake Hartwell. Testing was expanded in 2002, and is planned to continue for several more years, to include sampling and analysis of indigenous fish, plankton, clams, and invertebrates as a measure of the degree of recovery being achieved in the total Lake Hartwell ecosystem. This presentation covers the sediment and water chemistry data collected in 2000 and 2001.
Sample cores were divided into 5-cm segments and analyzed for 107 PCB congeners, thereby permitting PCB depth profiles to be plotted. Surface sediment concentrations of most of the transects sampled had reached or were approaching the
1.0 mg/kg total PCBs target. Age dating profiles using 210Pb isotopic measurements were also determined for those cores with a consistent depositional history. Congener analyses indicated increasing dechlorination was occurring with increasing sediment depth and age. Polytopic Vector Analysis resolved three end-member patterns resulting from the use of Aroclors 1016, 1242, and 1254 at the Sangamo-Weston facility and subsequent PCB dechlorination.