Delayed deposition of organochlorine pesticides at a temperate glacier

Many of the organochlorine pesticides that were once widely used have eithe r been banned or uses have been restricted in Canada and the United States. Near areas of high pesticide use at mid-latitudes in eastern North America , environmental levels of some of these pesticides peaked in the 1960s, and all have declined at least since the late 1970s. We determined depositiona l trends in a midlatitude temperate glacier in Alberta, western Canada (52 degrees N, 117 degrees W). In contrast to trends in eastern North America, Sigma DDT, dieldrin, and Sigma chlordane reached peak concentrations (2.57, 0.05, and 0.07 ng/L, respectively) and maximum flux to this cold high elev ation environment in the 1980s at least 1 decade after they had been banned and maximum use had occurred in North America. From 1959 to 1995, a signif icant decline was evident for alpha-HCH (r(2) = - 0.64, p < 0.001). A signi ficant severalfold increase and positive trend (r(2) = 0.17, p < 0.03) was evident for hexachlorobenzene with maximum flux occurring in the 1990s. Lin dane and Sigma chlordane had a distinct bimodal depositional pattern with p eak concentrations occurring about 1960 and again in 1989. Meltwater from g laciers may contribute high concentrations of pesticides to cold aquatic ec osystems for decades or centuries.