Environ. Sci. Technol. 2005, 39, 3538-3547
Long-Term Recovery of PCB-Contaminated Sediments at the Lake Hartwell Superfund Site: PCB Dechlorination. 1. End-Member Characterization V I C T O R S . M A G A R , * ,† GLENN W. JOHNSON,‡ RICHARD C. BRENNER,§ JOHN F. QUENSEN, III,| ERIC A. FOOTE,† GREG DURELL,⊥ J E N N I F E R A . I C K E S , †,# A N D CAROLE PEVEN-MCCARTHY⊥ U.S. Environmental Protection Agency, National Risk Management Research Laboratory, 26 West Martin Luther King Drive, Cincinnati, Ohio 45268, and Battelle Memorial Institute, 505 King Avenue, Columbus, Ohio 43201
Under anaerobic conditions, such as those typically found in buried sediments, the primary metabolic pathway for polychlorinated biphenyls (PCBs) is reductive dechlorination in which chlorine removal and substitution with hydrogen by bacteria result in a reduced organic compound with fewer chlorines. Vertical sediment cores were collected from Lake Hartwell (Pickens County, SC) and analyzed in 5-cm intervals for 107 PCB congeners in a total of more than 280 samples from 18 sediment cores and surface samples. This paper reports on extensive PCB dechlorination measured in Lake Hartwell sediments and the characterization of dechlorination end-member (EM) patterns using chemical forensic methods. PCB congener fingerprinting and a multivariate receptor modeling method, polytopic vector analysis (PVA), were used for identification and characterization of weathered and dechlorinated PCB congener patterns. Dechlorination resulted in a substantial shift in buried sediments from tetra- through decachlorobiphenyl congeners to mono- through trichlorobiphenyl congeners. Mono- through trichlorobiphenyls comprised ∼80% of the PCBs in buried sediments that underwent maximum dechlorination as compared to ∼20% in surface sediments. The major concentration decreases were seen in the tetra- through hexachlorobiphenyl homologues, which accounted for over 90% of the dechlorination. Octa- through decachlorobiphenyl congeners also were dechlorinated, * Corresponding author present address: ENVIRON International Corporation, 123 N. Wacker Dr., Suite 250, Chicago, IL 60606. Phone: (312)853-9430; e-mail:
[email protected]. † Battelle Memorial Institute. ‡ Permanent address: University of Utah, Energy and Geoscience Institute, Civil and Environmental Engineering Dept., 423 Wakara Way, Suite 300, Salt Lake City, UT 84108. § U.S. Environmental Protection Agency. | Permanent address: Michigan State University, 528 Plant and Soil Science Bldg., East Lansing, MI 48824. ⊥ Permanent address: Battelle Ocean Sciences Laboratory, 397 Washington St., Duxbury, MA 02332. # Present address: New Mexico Environment Department, Surface Water Quality Bureau, Harold Runnels Bldg., N2109, 1190 St. Francis Dr., Suite N2050, Santa Fe, NM 87502. 3538
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ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 10, 2005
but their overall contribution to dechlorination was relatively small due to their low initial concentrations (
