ECOLOGICAL RELATIONSHIPS OF PLUTONIUM 407 



accounts for about 90% of the annual precipitation. Tlie area supports a relatively dense 

 vegetation cover, considering the region; total vegetative ground cover ranges from about 

 15 to 25%(Neher and Bailey, 1976). 



On July 16, 1945. a 20-kt atomic bomb was detonated 31 m above the ground 

 surface at Trinity Site during a relatively unstable climatic regime when winds were to the 

 northeast and were accompanied by intermittent thundershowers. Fallout from the cloud 

 deposited in a northeast direction in the general pattern outlined in Fig. 1 (Larson et al., 

 1951 ). Relatively high fallout deposition occurred on Chupadera Mesa about 35 to 55 km 

 from the crater. The reasons for the heavy deposition in this zone are unknown but may 

 be related to weather or topographic factors. Tlie elevation increases from about 1 500 m 

 at the crater to 2100 m on Chupadera Mesa. The fallout zone within 15 km of the crater 

 is on the Wliite Sands Missile Range, which is under U. S. Army jurisdiction. Beyond 15 

 km the fallout zone is on mixed private and public (Bureau of Land Management, State; 

 and U. S. Forest Service) lands that are used heavily for domestic livestock grazing. 



Plutonium Distribution 



General 



The chronic release of treated liquid effluents to the Los Alamos canyons has resulted 

 in soil plutonium concentrations that are generally much higher than those at Trinity 

 Site. Concentrations of a few hundred picocuries per gram (dry weight) are found in soils 

 from the canyons, whereas those in Trinity soils average less than 1 pCi/g (Table 2). 

 Worldwide fallout concentrations of 2 3 9,2 4 op^^ ^ ^^ Alamos and Trinity Site soils 

 average about 0.01 pCi/g (Apt and Lee. 1976; Nyhan, Miera, and Neher, 1976b). 



TABLE 2 Ranges in Plutonium Concentration and Variability 



Estimates in Some Los Alamos and Trinity Ecosystem 



Components in 1973 and 1974 



*Dry-weight concentrations. 



tlncludes^^'Puand 2 3 9,2 4 op^, 



^Coefficient of variation (CV = standard deviation/mean). 



