Toxic contaminants in rainfall in Canada: 1984

Abstract

Replicate rain samples for most of the 1984 wetfall season were collected from four widely separated sites in Canada, and concentrations and loadings of a number of polychlorinated biphenyls and organochlorine pesticides were determined for each location. Comparisons were made among the sites and with results from other years. The major contaminants in 1984 were, in order of concentration, α-hexachlorocyclohexane (α-HCH or α-BHC), lindane and polychlorinated biphenyls (PCBs). Found at lower levels were dieldrin, methoxychlor (in the Lake Superior area), DDT residues, endrin (especially at Kouchibouguac), heptachlor epoxide and hexachlorobenzene. The loading of the α-HCH/lindane pair was higher at the Atlantic coastal site than at the other locations, possibly because of the greater precipitation there. No geographic trend for PCBs was apparent. For the other substances, no significant pattern to the differences between sites can be discerned. The qualitative similarities of concentrations and loadings at the widely separated locations, however, suggest long-range atmospheric transport. A comparison between results from two Lake Superior sites indicated no shoreline effect on the concentrations of over-lake versus shoreline samples. The differences observed were in accord with those observed in 1983 and were attributed to lack of replenishment from the lake surface.