Atmospheric transport of lindane (γ-hexachlorocyclohexane) from the Canadian prairies-a possible source for the Canadian Great Lakes, Arctic and Rocky mountains

摘要

Lindane (γ-hexachlorocyclohexane) is used as an insecticide in many countries. Concentrations of lindane have been found in air, water, soil, snow and tissue samples throughout the world, including the Great Lakes, and concerns have been raised for its potential effects on human and ecosystem health. In Canada, lindane was, until 2003, principally used as a treatment on canola seed, a crop grown mostly on the Canadian prairies. Approximately 455.3 and 510.4t of lindane were applied in May of 1997 and 1998 respectively. An estimated 12-30% of this lindane volatilised within the first 6 weeks after planting, resulting in an atmospheric loading of from 66.4 to 188.8t. Five-day forward air trajectories (movement) were calculated from three locations on the Canadian prairies, for the 6-week period following sowing of canola seed, to estimate if such movements might contribute to the seasonal increases of γ-HCH in five Canadian target locations. These target locations were: Point Petrie on Lake Ontario (eastern Great Lakes region); the Front Range of the Rocky Mountains of southern Canada; the low Canadian Arctic between latitudes 60° and 70°N; the central Arctic between latitudes 70° and 80°N; and, Eureka in the high Arctic, north of latitude 80°N. The percent of air mass trajectories moving from the prairies to these target areas was: Point Petrie 20%; Rocky Mountains 27%; low Arctic 30%; high Arctic 6%; Eureka 0%. It is possible, then, that volatilisation of γ-HCH from Canadian prairie canola crops contributed to the atmospheric loading in these remote regions.