444 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



All soil samples were screened to separate rocks greater than 0.6 cm in diameter from 

 the fine-soil component. Both size fractions were dried, and 100-g aliquots of the 

 fine-size (<0.6 cm) fraction and the entire large-size fraction were leached for about 16 hr 

 with a heated mixture of HCl and HF acids to dissolve the plutonium in the samples. 



Lichens were collected on an areal basis whenever possible to provide estimates of 

 biomass, community composition, and compartmental analysis for the various radio- 

 nuclides. Alaskan samples were 0.25-m^ blocks cut from the Cladonia Cetraria and 

 Alectoria-Cladonia-Cetraria fruticose lichen communities that form carpets on the 

 Anaktuvuk Pass (Fig. 1) landscapes. Greenland samples were obtained from several 

 discontinuous but representative "islands" of each community type which result from 

 microhabitat differences. The term "community" included all lichen or other plant 

 species (populations) within a sample and was designated by the dominant lichen species 

 at a specific location. The various dominant lichen species contributed an average of 90% 

 of the total community biomass in Greenland samples and 80% in the Alaskan samples. 

 Other populations separated from the community samples consisted of subordinate lichen 

 species, vascular plants, lichen and vascular plant debris, and fine soil, which normally 

 comprise a lichen community. The component samples were dried at 100°C for 24 hr to 

 determine dry weights and then dry-ashed at 425°C and dissolved in HCl and HF acids for 

 radiochemical analyses. An average of 1 to 5 g of ash resulted from minor sample 

 components, and up to 100 g of ash from major components of the populations was used 

 for plutonium determination. 



Eskimo residents of Anaktuvuk Pass provided the animal samples. Emphasis was 

 placed on sampling caribou (Rangifer arcticus tarandus) because of its importance as a 

 food base for the entire carnivore (including human) population in northern Alaska. 

 Major sampUng efforts were made in autumn (September— October) and spring 

 (May— June) months when the caribou were intercepted by Eskimo hunters during their 

 migrations to and from wintering grounds and summer ranges. Standard samples consisted 

 of the upper femur and attached muscle. Appreciable numbers of red foxes (Viilpes 

 fulva), tundra wolves (Canis lupus), and wolverines (Gulo gulo) and lesser numbers of 

 arctic foxes (Alopex lagopus) and lynx (Lynx canadensis) were taken each winter by 

 Anaktuvuk Pass Eskimo hunters; entire hindquarters of each animal type were obtained 

 for separation into muscle and bone samples, drying at 100°C. ashing at 425°C, and 

 subsequent radionuclide analyses. 



Cesium- 137 was measured by counting the 0.661 -MeV gamma-ray emissions from 

 dried soil, plant, and animal samples in a calibrated plastic container atop a 7.6- by 7.6-cm 

 sodium iodide crystal connected to a 400-channel analyzer spectrometer. Most counting 

 times for lichen samples were in the range of 30 to 40 min; counting times were longer 

 for small samples. Spectra were corrected to individual radionuclide amounts by 

 comparison with National Bureau of Standards sources and corrected for background- 

 radiation contributions. 



Plutonium-242 tracer was added to sample solutions to determine recovery of the 

 plutonium isotopes, and the mixture was deposited as the nitrate on an anion-exchange 

 resin column. The plutonium was eluted from the column with a nitric acid-ammonium 

 iodide solution and electrodeposited on stainless-steel planchets; the planchets were 

 counted on a silicon surface-barrier alpha spectrometer for 165 to 1330 min. Recovery of 

 plutonium isotopes, as measured by recovery of the ^^^Pu tracer, was usually in the 60 

 to 80% range. Isotopic exchange was considered to be uniform within the samples on the 

 basis of standards and interiaboratory comparisons. Counting efficiency for this particular 



