Studies of transuranic elements in arctic ecosystems

Cesium-137 and plutonium-238, 239, 240 were measured in soils and lichen communities of northern Alaska and Greenland during the period 1971-1974. Estimates of fallout deposition in the Thule, Greenland environs, as derived from soil samples, averaged 21.5 +- 2.4 (S.E.) nanocuries 137Cs per m2(= mCi/km2) in a range of 14.7 to 32.1. Highest values occurred in areas of snow accumulation. Inventories of fallout at Anaktuvuk Pass were determined in areal samples (0.25 m2) of continuous Cladonia-Cetraria lichen carpets. Cesium-137 inventories increased steadily from initial values of 6.2 nCi/m2 in 1962 to maximum values of 50 nCi/m2 in 1965 and have subsequently fluctuated near a median value of 35 nCi/m2. Preliminary measurements of 239240Pu in Alaskan lichen community samples yielded inventories of 0.28 to 0.33 nCi 239240Pu/m2, compared to a predicted inventory of 0.56 nCi/m2 based on a 239240Pu/137Cs ratio of 0.016 suggested as the ratio in soils. Lichens from several Thule locations during 1974 contained 0.26 +- 0.04 pCi 239240Pu per gram and a total inventory of 0.168 nCi/m2. This was about 20% of the plutonium inventory in the soils of the surrounding area. Isotopic ratios in soil, alluvium, and lichen samples were indicative of slightly greater amounts of 239Pu in Thule lichens than in Alaskan lichens during the period 1971-1974