426 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



TABLE 2 Distribution of ^ ^ ''Pu in Samples 

 from the Rocky Fiats Study Macroplot* 



*Compartmental ^^'Pu inventory (pCi/m^ ) equals mean biomass 

 [g(dry)/m^ ] times mean concentration [pCi/g(dry)] . Fraction of total 

 equals mean compartmental inventory (pCi/m^) divided by total 

 inventory. 



■[Number of samples for which the mean is calculated: For 

 arthropods and vegetation n is the number of groups of individuals 

 analyzed; for small mammals n is the number of tissue samples, not 

 individual animals. 



±95% confidence interval equals mean + (1.96 standard error of the 

 mean). 



§Includes data from Bly (1977). 



greater than 2.0. Although positive skewness is a characteristic of iognormal distributions, 

 the natural-log transformation of soil data did not result in normal distributions 

 (Kolmogorov— Smirnov one-sample test, P > 0.05) but did reduce the skewness for the 

 seven depth groups tested. 



Three adjacent soil columns (5 by 5 cm) from a 5- by 15-cm area on macroplot 2 

 exhibited the extreme spatial variability that sometimes occurred in plutonium 

 concentrations in the soil. The mean plutonium concentrations in the 5-g aliquots from 

 each column were 480 (column A), 5.4 (column B), and 0.57 pCi/g (column C) at the 0- 

 to 3-cm depth. Virtually all the plutonium in column A was in the top 3 cm, the other 

 depths (in 3-cm increments to 21 cm) being at or near background. In columns B and C, 

 the majority of the plutonium was found at lower depths. No other cases of such extreme 

 spatial variation in soil plutonium concentrations were detected during the sampling at 

 Rocky Flats. 



As expected, surface soil samples (0 to 3 cm) had a higher mean plutonium 

 concentration than subsurface samples (Table 3). This result agreed with data from 

 Rocky Flats soil sampling reported by Krey and Hardy (1970). Plutonium concentrations 

 were also a function of the size range of soil practices comprising the aliquot (Tables 3 

 and 4). 



