Environ. Sci. Technol. 2001, 35, 2903-2908
Polychlorinated Biphenyls in Nonaccumulating, Century-Old Sediments: Sources, Signatures, and Mechanism of Introduction JEFFREY R. CHIARENZELLI* Department of Geology, SUNYsPotsdam, Potsdam, New York 13676 CLARK ALEXANDER Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, Georgia 31411 ANN ISLEY Department of Earth Sciences, SUNYsOswego, Oswego, New York 13126 RONALD SCRUDATO, JAMES PAGANO, AND WALTER RAMIREZ
FIGURE 1. Diagram showing the location of Rice Creek and other localities mentioned relative to Lake Ontario and its drainage basin.
Environmental Research Center, SUNYsOswego, Oswego, New York 13126
congeners, in rural creek sediments lacking 137Cs and excess 210Pb.
Study Location and Analytical Summary This study documents the occurrence of highly chlorinated PCB congeners in stream sediment deposited over 100 years ago. Penta- to heptachlorinated congeners (>80%) have been found at concentrations up to 78.8 ng/g (dw) in core samples of a small, rural tributary of Lake Ontario. Lower chlorinated congeners and other organochlorine compounds occur sporadically; 210Pb and 137Cs are lacking. The most plausible mechanism is accumulation of dissolvedphase PCBs in permeable sediments adjacent to the creek channel. The similarity between core and air samples collected in the drainage basin suggests derivation from a residual fraction of atmospherically derived PCB congeners.
Introduction The limited solubility (1) and hydrophobicity of polychlorinated biphenyls (PCBs) suggests that their postdepositional migration within sediments by solubilization or molecular diffusion should be minimal. This is borne out in most core studies, and molecular diffusion coefficients of about (1-3) × 10-9 cm2/s have been modeled (2). Examination of core profiles has shown that mobility is generally proportional to aqueous solubility (2, 3). Postdepositional movement of PCBs is suspected when they occur in intervals dated prior to commercial production (4) or when vertical changes in congener or homologue distribution are noted (2-4). On a larger scale, lower ortho-chlorinated PCBs diffuse from pore spaces in contaminated sediments of the Upper Hudson River and dominate the dissolved PCB load of the river in the summer months (5). Such work demonstrates the predicted mobility of lower chlorinated PCBs in response to concentration gradients. Herein we demonstrate the occurrence of PCBs, dominated by highly chlorinated * Corresponding author phone: (315)341-2891; fax: (315)341-5346; e-mail:
[email protected]. 10.1021/es010593t CCC: $20.00 Published on Web 06/13/2001
2001 American Chemical Society
Rice Creek (RC) is a small, tannin-rich tributary of Lake Ontario that drains a rural, wooded area located just west of the Oswego River south of the city of Oswego (population
