Influence of chelating agents on the uptake of ²³⁹Pu and ²⁴¹Am by plants

Abstract

The uptake of ²³⁹Pu and ²⁴¹Am from two contrasting soil types, namely, a laterite (Oxisol) and a medium black (Vertisol-Pellustert) and also from nutrient solution as influenced by pre-chelation with synthetic chelating agents, DTPA and EDTA was studied. Results from soil-plant studies indicated a significant increase in uptake of ²³⁹Pu and ²⁴¹Am by plants from both soil types when added as ²³⁹Pu-DTPA,²³⁹Pu-EDTA,²⁴¹Am-DTPA or ²⁴¹Am-EDTA as compared to the treatments where transuranics were added in ionic (nitrate) forms. Concentration ratios (CRs) for Pu and Am in plant shoots increased by factors ranging from 3 to 700 depending on the soil type and the complexing ligand. Nutrient solution studies also revealed a marked enhancement in uptake as well as translocation of Pu and Am in plants due to supply of chelated transuranics. The shoots CRs in the case of Pu(NO₃)₄, Pu-EDTA, and Pu-DTPA were 0.11±0.02, 2.94±0.35 and 4.35±0.41, respectively. The observed values of Am CRs in shoots in the case of Am(NO₃)₃, Am-EDTA and Am-DTPA were 1.55±0.18, 1.86±0.25 and 2.85±0.40, respectively. An increase in the values of Transport index by 6 to 50-folds was observed in the case of Am and Pu, respectively, when added as chelates of DTPA in comparison to the nitrate form of the radionuclides. EDTA complexes of the transuranics were observed to be less effective than corresponding DTPA complexes in enhancing the uptake of Pu and Am by plants.