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Cold-condensation of organochlorine
pesticides and PCBs to northern and mountain environments.
Authors:
Jules M. Blais, University of Ottawa, 30 Marie Curie Rd., Ottawa,
Ont., Canada, K1N 6N5
David W. Schindler, University of Alberta, Edmonton,
Alberta, Canada, T6G 2E9
Derek C.G. Muir, Environment Canada 867 Lakeshore Rd., Burlington,
Ontario, Canada, L7R 4A6
Abstract: Organochlorine pesticides and
polychlorinated biphenyls (PCBs) are toxic and persistent in the
environment. They are known to concentrate in cold environments as
a result of progressive evaporation from warm regions, and
condensation in colder regions. Their hydrophobicity causes them
to assimilate rapidly in biological tissues, and as a result, they
may be biomagnified in food chains. A four-year program to study
transport and fate of persistent organic pollutants in alpine
environments in Banff National Park has revealed higher
concentrations of several organochlorine residues at higher
elevations relative to lower elevations. Inputs of these chemicals
by precipitation, stream flow, gas exchange, and losses by outflow
and sedimentation were quantified in alpine aquatic environments
to explain patterns of enrichment. More volatile organochlorine
compounds (HCH, HCB, endosulfan, heptachlor epoxide) concentrated
in snow and vegetation in higher elevation sites relative to lower
elevation sites. In contrast, concentrations of these compounds in
lake water showed no correlation with altitude. Rates of air-water
gas exchange for lakes spanning a range of elevations were
sensitive to fluctuations in air and water concentrations, and did
not show systematic patterns with respect to altitude and
temperature. Glacier melt water was the dominant source of many
organochlorine pesticides and PCBs to glacier-fed Bow Lake in
Alberta, based on a detailed mass balance for that lake in 1998.
These results show that mountain environments concentrate several
organochlorine pesticides and PCBs due to orographic and
hydrological effects.
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