Arsenic and copper residues in waterbirds and their food down inlet from the Island Copper Mill

Abstract

Since 1971, Island Copper Mine has been operating an open-pit mine, mainly for copper on the north shore of Rupert Inlet. Rupert Inlet is the most easterly inlet of Quatsino Sound on northern Vancouver Island, British Columbia (Fig. i). The ore body was estimated to contain 250 million tons of reserves. Mining is proposed to be continued until 1996, at which time the reserves will have been depleted (Island Copper Mine, pers. comm.). The mine processes daily 41,000 tons of ore, containing on average 0.52% copper (Waldichuk and Buchanan 1980). Mine tailings are discharged into Rupert Inlet at a depth of 50 m. The tailings now cover the bottom of Rupert Inlet (originally i00 m deep), as well as much of that of Holberg Inlet and part of eastern Quatsino Sound, past Quatsino Narrows (Fig. i). The tailings contain an average of about 700 mg/kg -I copper and 5 mg/kg -I arsenic (Thompson and Paton 1975). The concentrations of the same metals in natural sediments of Rupert Inlet are 44 mg/kg -I copper and 5 mg/kg -I arsenic (Waldichuk and Buchanan 1980). As chemical data were lacking, a pilot study was initiated in March 1976 to determine arsenic and copper residues in tissues of birds in Quatsino Sound and connecting inlets. After finding elevated arsenic residues in bird livers in 1976, waterbirds and their food chain were further investigated for arsenic and copper from October 1981 through March 1982. The results of the 1976 and 1981-82 analyses are presented here.