Patterns of contamination among vascular plants exposed to local sources of polychlorinated biphenyls in the Canadian Arctic and Subarctic.

Polychlorinated biphenyl (PCB) concentrations were examined in 1043 Arctic vascular plant specimens comprising 31 genera and the soils they grew in. The samples were collected at 61 abandoned military and Coast Guard sites across the Canadian Arctic and Subarctic and in nine remote background locations. Genus-specific differences in PCB uptake, partitioning of PCBs among different plant tissues, and congener-specific uptake of PCBs were examined. Mean PCB concentrations and plant vs. soil regression relationships were significantly different among genera. The highest concentrations were found in Poa and Luzula and the lowest mean concentration was found in Betula. Among the genera examined, PCB concentrations in the genus Luzula exhibited the greatest increase relative to increasing soil PCB concentrations. Bioaccumulation factors were not fixed within a single genus or species, but decreased with increasing soil concentrations, suggesting that at higher levels of exposure accumulation of PCBs may be kinetically limited by redistribution processes within the plant. The accumulation of specific congeners was related to the primary mode of exposure and the octanol-air partition coefficient (K(oa)) of the congener. In plants exposed mainly to atmospheric PCBs, uptake increased with increasing K(oa), as has been reported elsewhere. By contrast, there was a negative correlation between accumulation and K(oa) in plants that were mainly exposed through direct contact with contaminated soil. Only congeners 132/153 were found at concentrations greater than predicted from their K(oa). The presence of these congeners in plants is proposed as the explanation for their predominance in terrestrial animal tissues.