Radiocesium in caribou and reindeer in northern Canada, Alaska and Greenland from 1958 to 2000

摘要

This study summarizes the spatial and temporal trends of fallout ~(137)Cs concentrations in caribou and reindeer (Rangifer tarandus ssp.), reported in various programs in Canada, Alaska and Greenland, over a 40-y period. During the 1960s, the highest ~(137)Cs concentrations (2000-3000 Bq kg~(-1) wet weight in muscle) were found in the large caribou herds of central northern Canada, with levels about 50% lower in Alaska and Greenland. Concentrations varied by up to a factor of 6 between spring and fall. Concentrations in reindeer were comparable to those in caribou from the same regions. The highest ~(137)Cs concentrations (750Bq kg~(-1)) in the late 1980s were found in the Caniapiscau herd of central Quebec. The contribution from the Chernobyl accident in 1986 was estimated from ~(134)Cs measurements to be 10-40% of the total ~(137)Cs. Present concentrations have declined to 200-300 Bq kg~(-1). The effective half-life (T_(eff)) of ~(137)Cs in Canadian caribou herds was estimated to be about 6 y. The potential impact on the health of northern residents is discussed.