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Humic acids (HA) possess a strong ability for metal complexation. They can alter the migration of radionuclides inclay environments. Several studies have shown that some radionuclides are strongly retained in humics-rich surface soils [1, 2]. For example, the migration of Eu(III) in bentoniteis hindered by HA because of the formation of the Eu-HAcomplexes at the surface of compacted bentonite [1]. In addition, the diffusion of Cu(II) is prevented by humic gels andthe diffusion coefficient in the presence of humic gels is twoorders of magnitude lower than that in water [2]. However,humics also facilitate radionuclide transport by the formationof radionuclides-colloid complexes. Wold et al. [3] found thathumics could make the apparent diffusion coefficient Da increase and the distribution coefficient, Kd, values decreasefor both Co(II) and Eu(III) in compacted bentonite. |
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