Comparative Uptake and Distribution 

 of Plutonium, Americium, Curium, 

 and Neptunium in Four Plant Species 



R. G. SCHRECKHISE and J. F. CLINE 



The uptake of the nitrate forms of^^^Pu, '^^^Pii, '^'^^Am, ^ "* "* Cm, and ^ ^ "^ Np from soil 

 into selected parts of four different plant species grown under field conditions was 

 compared. Alfalfa, barley, peas, and cheatgrass were grown outdoors in small weighing 

 lysimeters filled with soil containing these contaminants. The plants were harvested at 

 maturity, divided into selected components, and radiochemically analyzed by alpha- 

 energy analysis. Soil concentration did not appear to affect the plant uptake of ^^^Pu, 

 ^^^Pu, ^^^ Am, or ^^^Cm for the two levels used. The relative uptake values of ^^^Pu 

 and ^^^Pu were not significantly different from each other and the ^'^ ^ Am uptake values 

 were not significantly different from the ^^'^Cm values. The relative plant uptake of the 

 four different transuranium elements was Np > Cm —Am> Pu. Relative uptake values of 

 neptunium into various plant parts ranged from 2,200 to 45,000 times as great as those of 

 plutonium, whereas americium and curium values were 10 to 20 times as great. The seeds 

 were significantly lower than the rest of the aboveground plant parts for all four 

 transuranics. The legumes accumulated approximately 10 times as much as the grasses. A 

 hypothetical comparison of the radionuclide content of plants grown in soil contami- 

 nated with Liquid Metal Fast Breeder Reactor fuels indicates that concentrations of 

 isotopes of americium, curium, and neptunium would exceed ^^^ Pu values. 



The release of transuranium nuclides to environmental systems, whether planned or not, 

 poses potential hazards^, especially if the biologically toxic materials enter food chains 

 leading to man. Quantitative information on transport parameters is required for an 

 assessment of the potential health hazards from such releases. One parameter that 

 warrants close attention is the plant uptake of transuranics from contaminated soil. It 

 used to be assumed that all transuranium elements behaved like plutonium and were 

 equally discriminated against by plants. However, studies by Cline (1968) and Schulz et 

 al. (1976) indicate a difference in the phytoavailability of ■^'^ ' Am and ^^^Pu. 



Variations in the relative uptake of plutonium by plants, as summarized by the 

 Energy Research and Development Administration (1975), can be explained by 

 differences in plant species or fragments examined. Other factors that affect uptake are 

 edaphic parameters, environmental conditions, and differences in the chemical form or 

 valence state of the plutonium initially added to the soil. This chapter reports the relative 

 plant uptake of ^^^Pu, ^^^Pu, '^^ 'Am, ^"^"^Cm, and ^^''Np from soil into selected parts 

 of four different plant species grown under field conditions. The data presented here are 

 first-year results of a long-term study of the effects of aging, weathering, and associated 

 biological processes in soil on the phytoavailability of transuranium elements. 



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