PCBs in sediments and the coastal food web near a local contaminant source in Saglek Bay, Labrador.

Polychlorinated biphenyls (PCBs) were measured in marine sediments and the coastal food web in Saglek Bay, Labrador, to investigate the influence of a local PCB source. Saglek Bay has been the site of a military radar station since the late 1950s and there was PCB-contaminated soil at a beach prior to cleanup in 1997-1999. PCB concentrations in marine sediments during 1997-1999 ranged from 0.24 to 62000 ng/g (dry weight) and decreased exponentially with distance from the contaminated beach. Given this gradient, spatial trends of PCBs in the food web were examined over four zones, according to distance from the contaminated beach: within 1.5 km--zone one, 1.5-4.5 km--zone two, 4.5-7.5 km--zone three, and greater than 7.5 km--zone four. PCB concentrations in a bottom-feeding fish (shorthorn sculpin, Myoxocephalus scorpius), decreased significantly from zone one to zone two, three, four, and distant Labrador reference sites. PCB concentrations in the eggs of a diving seabird (black guillemot, Cepphus grylle) were as high as 48000 ng/g during 1997-1999 and average concentrations in zones one and two were 84 and 13 times higher than in zone four. Marine invertebrates closely reflected the concentrations of PCBs in the associated sediment. In contrast to the benthic-based food web, anadromous arctic char (Salvelinus alpinus) showed no evidence of PCB accumulation from the contaminated sediments. Relatively high PCB concentrations were discovered in some great black-backed gulls (Larus marinus) and ringed seals (Phoca hispida) but appear to relate more to their high trophic level than sampling location. Those species that fed on or near the seabed and had limited foraging ranges were strongly influenced by the local contamination. Total PCB concentrations in the benthic-based food web were significantly higher than background levels for a distance of at least 7.5 km from the contaminated beach. This area is small in the context of widely distributed contamination from long-range transport but the area's high concentrations are comparable to levels associated with adverse effects elsewhere. Our findings should be useful to better assess the environmental impacts of PCB contamination at other coastal sites in the Arctic.

The relative influence of distant and local (DEW-line) PCB sources in the Canadian Arctic.

Soil PCB contamination has been delineated at 18 of 21 Distant Early Warning Line (DEW-line) stations being cleaned up by the Canadian Department of National Defence (DND). As a result, detailed surface soil delineation data has been reported for contamination exceeding 1 microg/g (dw total Aroclor), which is the remedial criteria for PCB contaminated soil under the DEW-line cleanup project. The results of this delineation work has allowed us to estimate the mass of PCB contained in surface soil at these sites and to quantify the DEW-line as a source of PCBs to both local and Arctic wide contamination. Our analysis of DEW-line cleanup delineation reports suggests that pre-cleanup surface soils (top 10 cm) with over 1 microg/g PCB constituted a source of PCBs that ranged from 0.8 to 43 kg with a mean of 18 kg. The total mass of PCB at all 18 sites was 119 kg. Previous studies have described a "halo-effect" that surrounds DEW-line sites, whereby PCB signatures in soil and plants up to 10 km from source areas were attributed to the local source. At Cambridge Bay (CAM-M), Nunavut, our inventory of PCB sources and redistribution suggests that up to 3.4 kg of PCB were exported from the site to the surrounding tundra prior to cleanup. The primary mechanism of transportation appears to be wind borne particulate. Potential vapour phase emissions of PCB from contaminated soil at DEW-line sites appears to have been negligible.