Geographic variation of chlorinated hydrocarbons in burbot (Lota lota) from remote Lakes and Rivers in Canada

Abstract

The variation in levels of polychlorinated biphenyls (∑PCBs), chlorobenzenes and chlorinated pesticides was studied in burbot (Lota lota) from eight remote locations along a northwesterly transect from northwestern Ontario to the Mackenzie River delta in Canada. Significant declines in concentrations of PCB congeners, DDT isomers (∑DDT), lindane, dieldrin, and mirex in burbot liver were found with increasing north latitude. Mean ∑PCB concentrations ranged from 1,290 ng/g (lipid wt) at Lake 625, a remote lake in northwestern Ontario, to 301 ng/g in samples from the Mackenzie River at Arctic Red River, N.W.T. No significant differences in mean concentrations of toxaphene, α-HCH, tri- and tetrachlorobiphenyls were observed between southern and northern sampling sites. Toxaphene was the predominant organochlorine residue in northern fish samples averaging 1,400 ng/g (lipid wt) at the three most northerly sites and 1,723 ng/g at Lake 625. Airborne contamination was the only likely source of organochlorine s for most of the locations surveyed. The results were consistent with the hypothesis that inputs of semi-volatile organochlorines to northern aquatic ecosystems decrease with increasing north latitude and distance from North American sources.