Mercury anomalies in lake water and in commercially harvested fish, Kaminak Lake area, district of Keewatin, Canada

Abstract

Mercury (Hg) was measured in approximately seven hundred samples of surface water collected from Kaminak Lake and nearby small and large lakes in a tundra environment located west of Hudson Bay. Mercury variations were expected to be related to sulphide mineralization, and patterns of Hg enrichment were to be used as pathfinders for locating potentially economic sulphide deposits. Water in the northern part of Kaminak Lake, which is underlain by sedimentary and volcanic bedrock with known potential for sulphide (base metal) mineralization, was consistently enriched in Hg, as were smaller lakes lying along the same bedrock trend. Mercury concentrations in lake trout from a commercial fishery on Kaminak Lake ranged from 0.57 ppm (parts per million = mg/kg or mg/l) to 2.0 ppm Hg (70 samples), exceeding the national consumption guidelines of 0.5 ppm. Subsequently, the Kaminak fishery was abandoned and relocated on nearby Kaminuriak Lake where similar fish species averaged less than 0.5 ppm Hg. High Hg concentrations in fish from this remote, unpopulated region, far from industrial sources of pollution, are related mostly or wholly to local geological phenomena.