Distribution of 137Cs in a Low Arctic Ecosystem in West Greenland

Abstract

During the summer of 1992, sampling of soil and vegetation was carried out at five localities in West Greenland to investigate the distribution of 137Cs in soil and in some reindeer fodder plants. Depending on the locality, between 69% and 97% of the total 137Cs deposition resided in the vegetation and upper 5 cm of soil. Between 0% and 15% had penetrated to depths lower than 10 cm. Both in the soil and in the vegetation, the concentration of 137Cs was in agreement with the degree of continentality estimated from the composition of plant communities; this agreement indicates a precipitation-related longitudinal gradient in the deposition of 137Cs along the coast of West Greenland. In leaves of Salix spp., the 137Cs concentrations in dry matter varied between 2 and 30 Bq per kg: the lowest concentrations were in Salix glauca growing on mineral soils in the continental inland of Sondre Stromfjord (Kangerlussuaq), and the highest concentrations were in Salix glauca growing in bogs at Skarvefjeld on the coast of southwestern Disko Island. In the two species of lichens, the 137Cs concentration pattern was similar to that of Salix, with a variation between 65 and 138 Bq per kg in Cetraria nivalis and between 209 and 305 Bq per kg in Cladina mitis. The ratio between the concentration (Bq per kg) in the plant and the ground deposition (Bq per sq. m), the Observed Ratio, or OR (sq. m per kg), was calculated for Salix, lichen, and moss species. The OR for Salix varied between localities, and ranged from 0.003 to 0.017 sq. m per kg. The OR of moss and lichen varied between 0.074 and 0.238 sq. m per kg; it was lowest in Cetraria nivalis and highest in Cladina mitis. Faecal samples of the wild reindeer, Rangifer tarandus groenlandicus, and the muskox, Ovibos moschatus, from Kangerlussuaq indicated that the reindeer eats plant species that are richer in 137Cs and poorer in potassium than those eaten by the muskox.