ECOLOGICAL RELATIONSHIPS OF PLUTONIUM 409 



Vertical Distribution. Some data from Area 21 (see Fig. 1) at Trinity Site indicate that 

 the plutonium originally deposited on those environs in 1945 has been depleted from the 

 soil surface over a 23-yr period (Table 3). Area 21 soils contained about 700 nCi/m^ in 

 1950 (Olafson. Nishita, and Larson, 1957) and 18 nCi/m^ in 1973 (Nyhan. Miera, and 

 Neher, 1976b). 



The depletion of plutonium from the soil surface is primarily due to the vertical 

 transport of the element into the soil profile rather than to horizontal transport away 

 from the study site by wind or water. Evidence that plutonium has migrated into the soil 

 profile at the two Trinity Site locations is illustrated in Table 4 and is presented in detail 

 by Nyhan, Miera, and Neher (1976b). In 1973 plutonium was detected at the 28- and 

 35-cm depths at Areas GZ and 21, respectively, whereas in 1950 plutonium was confined 

 exclusively to the surface 2.5 cm (Olafson, Nishita, and Larson, 1957). The patterns of 

 distribution with depth were typical of those observed in terrestrial soils in that 

 plutonium concentrations decreased with depth. 



TABLE 3 Comparison of Plutonium Concentrations 



in Surface (0 to 2.5 cm) Soils from Chupadera Mesa 



as a Function of Time After the Atomic Bomb Test 



at Trinity Site in 1 945 



Plutonium concentration, nCi/m- 

 1950* 1951* 1973t 



746{0.31)t 341(0.82)$ 18(0.48)* 

 n=6 n=3 n=8 



*Data for 1950 and 1951 from Larson et al. (1951), 

 and Olafson, Nishita, and Larson (1957). 



+ Data for 1973 from Nyhan. Miera, and Neher (1976b). 



^Parenthetic value is coefficient of variation 

 (CV = standard deviation/mean). 



TABLE 4 Mean Percent Plutonium Inventory in Soil Profiles from 

 Los Alamos and Trinity Site Study Locations in New Mexico 



*n = 8 for Trinity Site data; n = 10 for Los Alamos data. 



fParenthetic value is coefficient of variation (CV = standard deviation/mean). 



$Not detectable. 



