Transfer of radiocaesium from lichen to reindeer

Abstract

After the C h e r n o b y l accident i n apri l 1986 a large part of the reindeer hearding area i n Sweden was contaminated w i t h radioactive caesium ' 1 3 4 C s and 1 3 7 C s ) . Lichens the main winter forage for reindeer were heavily contaminated. Large intake of lichens i n the winter results in high activity concentrations of radiocaesium in reindeer in contaminated areas. A c t i v i t y concentrations of 1 3 7 C s in reindeer meat f rom five saami villages has been compared to the levels in lichens and to the deposit of 1 3 7 C s per m 2 ground surface in these saami villages (Table 1). The amount of 1 3 7 C s i n reindeer meat (Bq/kg) in the first winter after the C h e r n o b y l accident was approximately at the same level as the amount in dry lichens ( B q / k g dry weight) in June-October 1986 (from Er iksson et al, 1987) an w i t h i n the range of the deposit per m 2 (from map by S G A B , 1986). D u r i n g the late sixties, after the nuclear weapons tests, caribou in Alaska had levels of radiocaesium in muscle about one th i rd of the levels in dry lichens (Luick , 1974). Liden and Gustafsson (1967) reported levels of 1 3 7 C s in reindeer meat in the years 1961-65 to be about 50 % of the content of 1 3 7 C s in one m 2 of l i chen carpet. Factors that influence the biological halflife of radiocaesium in reindeer, e.g. total food intake, metabolic activity and amount of potassium and fibre in the diet, should also affect the level of radiocaesium in the body at a given daily intake. The amount of lichens in the diet w i l l thus be an important factor, since lichens contain on ly small amounts of potassium and protein. Jones et al. (1989) has calculated fractional