The effects of picolinate, an organic ligand used to decontaminate nuclear reactor cooling systems, in leachates generated from shallow-land burial (SLB) of low-level nuclear wastes (LLW) on soil adsorption was determined. Using batch adsorption tests and varying the con-centration of picolinate, the adsorption tendencies of two metals [Ni(II) and U(VI) and the ligand were measured as a function of solution pH. We found that when total metal concentra-tions were fixed at 10~(-5) M, picolinate at ligand-to-metal [L:M] ratios >= 10 did significantly reduce adsorption of Ni but even at a L:M ratio of 100 there was no effect on U(VI) adsorption. These results are compared with data on other metals in the presence of picolinate and for metal adsorption in the presence of EDTA. We conclude that picolinic acid is less of a threat than EDTA in waste leachates to reduce metal adsorption (increase mobility) and that picolinate concentrations must reach or exceed 10~(-4) M for the most impacted metals (i.e., those that form the very strongest complexes with picolinate). There are no leachate data on these decontami-nation agents for the common burial technique (disposal of de-watered resins in high integrity containers) that can be used to evaluate potential hazards of these organo-radionuclide complexes.
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