456 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



Britain, Russia, and the United States, the first and most sustained during 1953 to 1959 

 and the second during 1961 to 1964. Recent additions of fallout have been made by 

 atmospheric tests conducted by France and the People's Republic of China; tests 

 conducted during the summers of 1973 and 1974 by China have apparently made 

 important contributions of radionuclides of interest in this chapter. 



Estimates of ^^^'^''"Pu fallout inventories in the Arctic landscapes discussed in this 

 chapter began during 1959 and 1960 and have recently been estimated to be 0.33 

 mCi/km^ at Thule, Greenland, and 0.40 to 0.60 mCi/km^ in northern Alaska. If an 

 average ^^^'^^^Pu/^^'^Cs, ratio of 0.016 is assumed, these values translate to 20.6 mCi 

 ^^''Cs/km^ at Thule and 35.6 mCi '^^Cs/km^ at Anaktuvuk Pass. This is reasonably 

 close to the amounts calculated from HASL fallout deposition data for the period after 

 1959 and 1960, when the measurements began. A large increment of the pre-1959 fallout 

 is therefore unaccounted for in both the soils (to a depth of 5 cm) and lichen 

 communities studied in this chapter. The lichen communities of northern Alaska during 

 1964 contained 41 nCi ' ^ ^Cs/m^ (mCi/km^), and values since that time have fluctuated 

 near 35 to 40 nCi/m^ . This is equivalent to a predicted level of 0.56 to 0.64 nCi 

 239,240p^/j^2 j^^^g^ Qj^ ^j^g assumption of a ^^^'^"^^Pu/'^ ^Cs ratio of 0.016. However, 

 measurements of ^^^Pu and ^^^'^'^^Pu in lichen samples were about one-half the 

 predicted concentration. This lower value was confirmed by consistently lower 

 239,240py|i 3 iQ^ ratios (near 0.006 to 0.012) in Hchens during recent years. 



Isotopic ratios in Greenland soil and alluvium samples during 1974 were in the range 

 of 0.011 to 0.014 for "^'^^°Pu/^^^Cs and 0.010 to 0.019 for ^^^Pu/^^^'^^^Pu. 

 Although these values do not strongly indicate the presence of plutonium released by the 

 1968 aircraft accident that deposited an estimated 1 to 5 Ci of ^^ ^'^'^'^Pu on the Thule 

 landscapes, the ratios are substantially lower than the 0.020 to 0.024 values usually 

 found. The presence of 2 3 9,24 0p|j pa^^j^-igs j^ soils, alluvium, and lichens of the Thule 

 environs in both 1968 and 1974 samples from sites south and southwest of the 1968 

 crash site was inferred from the extreme variation in sample aliquots from those areas. 

 Uncontaminated areas of Thule showed a more balanced distribution of plutonium 

 concentrations in soil and lichens, probably because of the edaphic and climatic factors of 

 the region which resuspended soils to a considerable degree. 



Samples of soils and lichens from northern Alaska contained lower plutonium 

 concentrations in relation to fallout deposition than were noted in Thule samples. 

 Lichen/soil ratios during 1975 and 1976 were 0.92 and 13.0, respectively; this contrasts 

 with the plant/soil ratios that are often of the order of 10""* to lO"'' in Temperate Zone 

 environments (Francis, 1973). Caribou/lichen ratios of ^^^'■^'^^Pu concentrations were in 

 the range of 10"^ to 10^'* , and carnivores contained transuranic nuclide concentrations 

 that were equal to or less than those in caribou, which were undoubtedly their major 

 food source. 



Acknowledgments 



I am grateful to Mary Ann Hanson for long hours spent in the meticulous separation of 

 the lichen sample components; to Eliza Trujillo, William Goode, and Kenneth Bostick 

 for laboratory assistance; and to Daryl Knab, Richard Peters, and David Curtis for 

 plutonium analyses. Gary White assisted in statistical analyses of the data. Ludi Kupinski 

 and Karen Tallent rendered secretarial and editorial assistance. This work was performed 

 under U.S. Department of Energy contract No. W-7405-ENG-36. 



