PLANT UPTAKE OF 237Np, 239,240Pu, 241Am, AND 244Cm FROM SOILS REPRESENTING MAJOR FOOD PRODUCTION AREAS OF THE UNITED STATES

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Abstract
Crops of peas, soybeans, tomatoes and wheat were grown in 7 different soils contaminated with mixtures of 237Np, 239,240Pu, 241Am and 244Cm. The soils were representative of major food production areas of the USA. The plant uptake experiments were performed in 200-l containers to simulate field conditions. Crop yields varied with the fertility conditions of the soils. Differences in soil properties were a major cause of variability in the concentration ratios (CR) that measured transuranic element uptake by food crop plants through root systems. Root uptake of 239,240Pu was lowest, with CR values for vegetative parts of plants ranging 10-6-10-4. CR values for 241Am and 244Cm were essentially the same, ranging 10-5-10-2. CR values for 237Np in vegetative parts ranged 10-4-10-1. CR values for seed, grain and fruit parts of plants generally were a factor of 10 lower than values for foliage (10-7-10-5 for 239,240Pu, 10-6-10-4 for 241Am and 244Cm and 10-5-10-3 for 237Np). From 60-90% of the variation for a given crop and radionuclide was attributable to soil difference; from 10-40% was attributable to differences between soil replicates and between samples from the same container. Plant uptake of 237Np through roots was .apprx. 1000 times greater than plant uptake of 239,240Pu; the uptakes of 241Am and 244Cm were essentially equal. Root uptake of 237Np was 60-70 times that of 241Am and 244Cm and 241Am and 244Cm were taken up .apprx. 20 times more than 239,240Pu under the same cropping conditions.