428 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



2 5 10^ 2 5 io3 2 5 



DISTANCE EAST OF ASPHALT PAD (E), m 



Fig. 3 Plutonium concentration in 0- to 3-cm-deep Rocky Flats macroplot 1 soil as a 

 function of distance east of the center of the asphalt oil-barrel storage pad. 



relationships, a power-function regression model had the highest correlation of plutonium 

 concentration with depth of the models attempted and was significant (P < 0.01). 



The relationship of plutonium concentration in soil as a function of soil particle 

 diameter (as represented by the opening of the final passage sieve) was examined for each 

 depth layer (Table 4). The model resulted in a significant (P < 0.05) regression for each 

 depth group except the 18- to 21 -cm group. The steepest slope (—0.799), at 12 to 15 cm, 

 was significantly different (P < 0.05) from the flattest slope (-0.270), at the 3- to 6-cm 

 level. However, there was no obvious trend in slope vs. soil particle-size curves with depth. 

 Because the amount of surface area represented by the soil particle spheres in a constant 

 mass of soil is inversely related to soil particle diameter, it followed that the plutonium 

 concentration in a soil sample should be inversely related to the surface area of the 

 particles in the sample. A tabulation of the fractions of the total soil-sample mass 



