Transuranic Elements in Arctic Tundra 

 Ecosystems 



WAYNE C. HANSON 



Concentrations and inventories of worldwide fallout of^^'^Cs, ^ ^ ^Pu, and ^ ^ ^ '^ '* '^pu ifj 

 soils, lichens, and animals from northern Alaska and Greenland during the period 

 1968-1976 are discussed. Cumulative ^^^Cs fallout deposition at the soil surface at 

 Anaktuvuk Pass, Alaska, during the period 1959-1976 was estimated to be 43 mCi/km^ , 

 compared to 16 mCi/km^ at Thule, Greenland. Measured ^^^Cs values in surface (top 

 5 cm) soil were 7.9 mCi/km^ at Anaktuvuk Pass and 21.5 mCijkm^ at Thule. The 

 discrepancy is presumably due to measuring difficulties and to rapid movement of 

 radionuclides into the soil profiles. An effective half-time of 0.4 to 0.5 yr was estimated 

 for Plutonium isotopes in surface soil at Anaktuvuk Pass. Average concentrations and 

 inventories of 239,240^^^ -^^ uncontaminated Thule lichen communities were, re- 

 spectively, 0.25 pCi/gand 0.21 nCi/m^ in 1968 and 0.33 pCi/g and 0.25 nCi/m^ in 1974; 

 however, these values were not significantly different. Inventories of ^^^Pu and 

 23 9,240^ w Alaskan lichen carpets were 0.019 and 0.28 nCijm^ , respectively, in 1968 

 and 0.040 and 0.67 nCi/m^, respectively, in 1974. Concentrations of^^ '' Cs, ^^^Pu, and 

 2 3 9,2 4 0p^^ were significantly higher in the upper 6-cm stratum than in the lower 6-cm 

 stratum o/Cladonia— Cetraria lichen carpets at Anaktuvuk Pass; concentrations of ^^S'r 

 were less consistent. 



Radionuclides in arctic ecosystems have been investigated for nearly 20 yr because of the 

 efficient transfer of worldwide fallout materials through arctic food chains. Initial 

 investigations were .concerned primarily with the radiological health aspects of the 

 appreciable body burdens of ^*^Sr and '^^Cs obtained by circumpolar populations that 

 were involved in the lichen— reindeer/caribou-man/carnivore food webs. The discovery of 

 measurable amounts of ^ ^ ^Cs in Nearctic Eskimos and Indians and Palearctic 

 reindeer-herding peoples in 1961 and 1962 coincided with the advent of a second major 

 period of nuclear weapons tests, which resulted in appreciable radioactive fallout 

 deposition and increased the efforts of several investigators. 



Several ecological aspects of arctic tundra ecosystems recommended them for study 

 of the transfer of worldwide fallout radionuclides. Although their geographical location, 

 mostly beyond 60°N latitude, is a region of appreciably less fallout deposition than other 

 more-populated areas of the world, the plant and animal communities are so related that 

 ^^^Cs body burdens of the native peoples in the Arctic regions, for example, are often 

 100 to 1000 times greater than those of Temperate Zone residents. This has resulted from 

 the effective accumulation of atmospheric materials, radioactive or otherwise, by the 

 hchen communities, which provide a reservoir of such materials at the base of northern 

 food webs. Transfer from this relatively rich soufte is enhanced by (1) the low 



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