346 TRANS URANIC ELEMENTS IN THE ENVIRONMENT 



alfalfa and 17 for barley). This effect may indicate loss of DTPA from the soil with time, 

 possibly by metabolism and degradation. 



Soybean Experiment. Results from the barley and alfalfa experiments showed the 

 necessity of using soils containing higher levels of contamination for better accuracy of 

 determination. In addition, the response from the soil amendments indicated a practical 

 influence from only the DTPA. Consequently the soybean experiments were conducted 

 using only chelate treatment of soils collected from eight of the Nevada Applied Ecology 

 Group study areas (Dunaway and White, 1974). Results of radiochemical analyses for 

 ^•^^Pu and ^"^^ Am are shovm in Table 6 and indicate that the CR values were higlier for 

 soybean leaves and stems (Table 6) than for either barley or alfalfa (Table 5). Different 

 soil sources, in part, were involved, but this may not be the major factor. The mean CR 

 values. for soybean leaves and stems were 1.4 x 10~^ and 3.7 x 10~^ for plutonium and 

 americium, respectively; with DTPA they were 4.4 x 10"'* and 6.5 x 10~^ , respectively, 

 which are higher than equivalent values for barley and alfalfa. 



The mean americium/plutonium ratio was 21.6, which is higher than that for either 

 barley (4.2) or alfalfa (9.9). It was not possible to determine if this ratio for soybeans 

 differed because of variability in soils. 



The DTPA enhanced the uptake of both plutonium and americium from the Area 1 1 

 and Area 13 soils but only slightly over those from the Tonopah Test Range. For the 

 Area 11 soils, DTPA increased the uptake of americium more than of plutonium (about 

 2.5 times). This result did not appear to be significant since it was not observed for the 

 other soils described in Table 6 except for one. Different chemical and physical properties 

 of americium and plutonium in the soils from different locations may be involved. The 

 soil plutonium/americium ratios were highest (Table 1) for the soils with least response to 

 DTPA. 



The mean CR for fruit pods was 3.7 x 10"^ for ^^^Pu and 8.0 x lO"'* for ^"^^ Am. 

 Without DTPA the values were 1.5 x 10~^ and 3.1 x 10"'', respectively. The mean 

 americium/plutonium ratios were slightly higher for fruit pods than for vegetative 

 material (32.8 vs. 21.6). The mean americium/plutonium ratio for fruit pods was 23,6 

 without DTPA and 42.0 with DTPA. The difference, however, was not due to 

 DTPA-induced transport from leaves to fruit because the americium/plutonium ratios 

 with and without DTPA were really not different (Table 6). Also, the mean CR for 

 vegetative parts for plutonium was 9.9 without DTPA and 11.5 with DTPA, which 

 difference was not significant. For americium the means were 15.9 and 10.1, the lower 

 value being with DTPA. It appears that DTPA caused more plutonium and americium to 

 be translocated to the fruit pods because plutonium and americium were liigher in the 

 leaves when DTPA was added. This resulted in correlation coefficients of +0.988 for 

 plutonium and +0.983 for americium between these two plant parts. The CR values for 

 fruit pods vs. leaves and stems from the eight soils were calculated for plutonium and 

 americium and show that, on the average, the ratios were 0.035 ± 0.003 SE for ^^^Pu 

 and 0.058 ± 0.009 SE for ^"^^ Am. The americium/plutonium ratio was 1.7 ± 0.24 SE for 

 the eight soils. The ratio of transport with DTPA to that without DTPA was 

 1,0±0.21SE for plutonium and 1.3 ± 0.36 SE for americium. This method of 

 calculation indicates that DTPA did not directly increase plutonium and americium 

 transport to fruits, nor did DTPA influence the two elements differentially in transport 

 from shoots to fruits. It appears tlierefore tliat there was a mass-action effect for 

 transport from leaves to fruit. 



