Polychlorinated Biphenyls in South Yukon Soils

Soils were sampled to determine concentrations of polychlorinated biphenyls (PCBs) at the Range Road dump site near Whitehorse and at Lake Laberge and Kusawa Lake in the Yukon Territory. Concentrations at the dump site ranged from 15-145 ng/g, while concentrations at Laberge and Kusawa ranged from 5-29 and 3-34 ng/g, respectively. The concentrations of PCBs in samples from Range Road were significantly different from both Laberge and Kusawa (t=l.94 > 1.76 and t=2.1 > 1.78 at 10 % significance, respectively). Conversely, the two lake sites were in agreement with the null hypothesis that the samples were drawn from the same population (t=0.243 < 1.771 at 10 % significance). Individual PCB congener concentrations revealed a significant correlation (r > 99.9) between one Range Road sample and Aroclor 1260, and chlorine homologue distributions for all dump site samples displayed a predominance of heavier homologues implying that the dump site is locally contaminated rather than receiving contamination via atmospheric input only. On the contrary, the pattern of chlorine homologue concentrations for the lake sites suggest mainly atmospheric sources since the majority of PCBs were comprised of the less chlorinated homologues, which is consistent with long-range atmospheric transport of organochlorine chemicals. Although background concentrations of PCBs determined for the lake sites are in agreement with published reports for other sites receiving atmospheric contaminants, there is the possibility that the Laberge and Kusawa samples overestimate the actual PCB levels in the soils. Low levels of some congeners were detected in procedural blanks, which probably resulted in elevated concentrations of PCBs in some of the soil samples.