Trends and seasonality in α- and γ-hexachlorocyclohexane in western Canadian surface waters (1975-94)

Surface water monitoring results (1975-94) for alpha-hexachlorocyclohexane (alpha-HCH) and gamma-hexachlorocyclohexane (gamma-HCH, lindane) from nine sites in the Canadian prairie provinces were examined for long-term trends and seasonality. The monitoring sites represented four major ecozones of the prairie provinces, including agricultural and non-agricultural areas. Decreasing trends in alpha-HCH concentration and detection frequency were found at all sites, likely related to decreased use of technical HCH world-wide. Inter-site alpha-HCH detection frequency was comparable and intra-site seasonal variability was minimal at agricultural and nonagricultural locations, providing evidence of long-range atmospheric transport. gamma-HCH concentration and detection frequency did not change significantly during the study period at most sites, consistent with relatively static use patterns in western Canada. gamma-HCH detection frequency was higher, and seasonality more pronounced, at agricultural sites than at non-agricultural sites, suggesting that gamma-HCH present in prairie surface waters was related to regional, rather than global, use of lindane. (C) 1998 Elsevier Science Ltd. All rights reserved.