424 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



(1 ha = 2.5 acres) and contained 100 sampling markers. Plutonium data in this chapter are 

 from macroplot 1 unless specifically noted otherwise. 



Depth-profile soil samples were taken by hand with a trowel. After vegetation and 

 litter had been clipped and bagged separately, four 5- by 5- by 3-cm samples were 

 removed and bagged separately for each of seven 3-cm-depth layers to 21 cm deep. If 

 rocks precluded sampling at a given depth, the column was resumed below the blockage. 

 Soil samples were transported to the laboratory and air-dried. Rocks or debris greater 

 than 0.5 cm in diameter were removed from the sample. After oven-drying and weighing, 

 samples were mechanically shaken on brass soil sieves. The accumulation on each sieve 

 was weighed and placed in a small paper envelope, and the envelope was sealed with tape. 



Litter and standing vegetation were sampled from 0.25-m^ and 0.5-m^ areas, 

 respectively. Vegetation was clipped and bagged, and litter was gathered by hand and 

 bagged. In the laboratory litter and vegetation samples were air-dried and weighed. Soil 

 was separated from the Utter samples by a flotation process (Little, 1976). The net 

 vegetation or the litter dry weiglit was divided by the microplot size, 0.5 m^ or 0.25 m^ , 

 respectively, to calculate mass per unit area. For plutonium analysis vegetation and Utter 

 samples were ground on a Wiley mill with an SSO-jLim opening screen, and 5-g aliquots 

 were taken. 



Arthropods were sampled by a combination of sweep netting, pitfall trapping, and 

 drop trapping at random sites on established grids. At the laboratory animals were 

 separated into generic groups that were weighed separately. These generic totals were 

 combined for an estimated weight per 0.5-m^ microplot. Arthropods obtained by the 

 drop-trap method were not analyzed for plutonium owing to fear of cross contamination 

 from soil during the vacuuming process. Samples for plutonium analysis and a species 

 inventory list resulted from the sweep netting and pitfall traps. For plutonium analysis a 

 representative composite was analyzed for each sampling period. Arthropods were not 

 cleaned prior to plutonium analysis. 



Small-mammal trapping grids were superimposed over each macroplot in a manner 

 resembUng that used by the U. S. International Biological Program Grassland Biome 

 (Packard, 1971). Animals were trapped about six times yearly. Sherman live traps were 

 used for cricetid and sciurid rodents. Geomyid rodents were trapped less regularly in 

 homemade live traps placed in burrows systems. Approximately 15% of the estimated 

 population was removed from each macroplot during each trapping session. These animals 

 were coUected by removing dead-in-t^ap individuals during the regular session and the 

 remainder randomly in one extra trapping night. Small mammals were either dissected 

 immediately or frozen for dissection later. Special precautions were taken during 

 dissection to minimize cross contamination between tissues. Approximately 10 cm^ of 

 hide was used as an aUquot. Lungs, liver, and gastrointestinal (GI) tract were removed 

 intact. Muscle samples were taken from the legs in most cases. Bone samples consisted of 

 the whole skeleton, which had been cleaned of flesh by a dermestid beetle colony. All 

 samples except bone were placed on tared, ashless filter papers, oven-dried at 50 to 60°C, 

 and weighed. The sample was placed in a snap-cap vial for storage or transport to a 

 commercial laboratory. 



Some soil-sample aliquots (5 g) were analyzed for plutonium content by commercial 

 laboratories (LFE, Richmond, Calif., and Eberline Instrument Corp., Albuquerque, 

 N. Mex.). Most soil samples were analyzed in our laboratory, as were most litter and 

 vegetation samples. Small-mammal tissues and arthropods were commerciaUy analyzed. 

 The LFE method used concentrated hydrofluoric acid to dissolve samples (Wessman 



