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Matsunaga, Takeshi; Nagao, Seiya*
Humic Substances Research, 5/6(1), p.19 - 33, 2009/00
The environmental behavior of Chernobyl-derived plutonium has been reviewed in the soil and the aquatic environment in Ukrainian affected areas. Dissolution of released fuel particles was an initiation for migration in the environment for the Chernobyl-derived plutonium. Once dissolved, the plutonium distributed persistently over surface soil layer with a limited infiltration ability. This relative immobility of plutonium in the soil environment can be attributed to its affinity for soil organics, based on chemical partitioning investigations. The relative immobility of plutonium was also seen in its fluvial transport along the Dnieper River. Dissolved organic matter, most probably humic substances, helped stabilize dissolved plutonium in the lake waters.
Tanaka, Tadao; Mukai, Masayuki
Humic Substances Research, 5-6(1), p.35 - 43, 2009/00
The present paper describes a theoretical evaluation of the influence of humic-complexation on migration of cationic radionuclides through porous media, where it is assumed that complexation reactions between radionuclides and natural organics, such as humic acid and fulvic acid, can be regarded to follow an instantaneous equilibrium or a first-order kinetic reaction. The calculation results revealed that radionuclide migration in the presence of humic substance was predominantly controlled by relative magnitude of distribution coefficients between the cationic radionuclides and the complexed radionuclides. Radionuclide migration was also affected significantly by the stability of the complexes or the rate constants of the complexation reaction.
Nagao, Seiya*; Sakamoto, Yoshiaki; Rao, R. R.*; Fujitake, Nobuhide*
Humic Substances Research, 5-6(1), p.9 - 17, 2009/00
Sorption behavior of Np(V) onto sandy materials (sand, tuffaceous sand and sandy rock) was studied in the absence and presence of humic substances (HS) using a batch method at pH 5-6 and ionic strength of 0.01M. The effects of shallow land groundwater HS on the Np(V) sorption depend on the mineralogical components of sandy materials. The distribution coefficient (Kd) of Np(V) increased in the presence of HS. The Kd values were in the order of sand
tuffaceous sandsandy rock samples. The Np(V) sorption in the presence of HS with different origin for the sandy rock sample was divided into two groups. The Kd values were positively correlated with aliphatic carbon contents of the lake and the shallow groundwater HS, except for the deep saline groundwater HS. These results indicates that the characteristics of the sandy materials and groundwater HS are important factors determining the Np(V) sorption because of the presence of Np(V)-bound HS.