344 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



TABLE 4 Influence of Chelate DTPA and Organic Matter on 



^^ ^ Am Concentration Ratios for Rice Grown in a Southeastern 



U.S. Soil Under Flooded and Nonflooded Conditions*! 



Unshelled 

 grain/soil 



Green blades/soil Old (dead) blades/soil 



Flooded 



(2.6 ± 0.80) X I0-' 

 (0.2 ± 0.85) X 10-' 

 (7.6 ± 2.4) X 10-^ 



Nonflooded 



(2.7 ± 0.18) X 10~' 

 (2.9 ± 0.67) X 10"' 

 (1.4 ± 0.22) X 10"-' 



(2.5 1 0.22) X 10-' 

 (2.8 ± 0.27) X 10"' 

 (1.5 ± 0.31) X 10"' 



(5.9 ± 1.3) X 10-' 

 (2.2 i 0.76) X 10"' 

 (1.5 ± 0.10) X 10"' 



* Values are means of five replicates ± standard error. 



fConcentrations in plant materials can be calculated from the CR values and 

 the assumed ' " ' Am concentrations (400 pCi/g soil or 435 pCi/g soil + 5% OM) of 

 the potted soil. 



:}: Activities were below the detection limit. 



have an influence on its availability to the rice plants; i.e., application to the standing 

 water is more likely to result in higher uptake. 



Rice has a peculiar uptake— translocation physiology (Chandrasekaran and Yosliida, 

 1973; Myttenaere and Marckwordt, 1967; Myttenaere, Bourdeau, and Masset, 1969). Its 

 only organ of economic importance is the grain. The straw is seldom used for animal feed. 

 Tlie "^' Am did not appear to be readily translocated to the grain; therefore its health 

 hazard to man is minimized. 



Soils from tM Desert Environment of the Western 

 United States 



Barley and Alfalfa Experiment. Results indicate that ^'^ ' Am generally was taken up 

 by barley two or more times as readily as was -^^^Pu (Table 5). The exception was for the 

 treatment acidified with sulfur and with DTPA. The reason was a relatively large uptake 

 of ^^^Pu with DTPA. The americium/plutonium ratios (Table 5) were obtained from the 

 respective CR values to normalize the levels in the soil. The CR values were generally in 

 the 10"^ to 10^ range (mean ^ '"^Pu^ 9.4 x lO""* and ^^' Am = 1.4 x IQ-^). 

 Without DTPA they were 1.3 X 10""* and 3.2 x 10"'*, respectively, for plutonium and 

 americium. Except for the control, which produced poor growth, DTPA enhanced the 

 uptake of both plutonium and americium. However, the increase, wliich was usually 

 greater than one order of magnitude, was equal for both elements. 



The CR values for alfalfa were slightly less than those for barley (Table 5). The mean 

 CR for 2 3 9pu ^as ^ ^^ jq-^ ^^^ ^^^ ^"^^ Am ^Jvas 9.3 x 10"^. Without DTPA the CR 

 values were 7.6 x 10~^ and 6.6 x lO^'*, respectively. The preference for americium over 

 plutonium (9.9) was greater in alfalfa than in barley (4.2). The DTPA had much less 

 effec^t on the uptake of the two elements by alfalfa than by barley (ratio of about 2 for 



