Europium-binding abilities of dissolved humic substances isolated from deep groundwater in Horonobe area, Hokkaido, Japan
北海道幌延地域の深部地下水から分離精製した溶存腐植物質のユーロピウムとの結合能
寺島 元基 ; 長尾 誠也*; 岩月 輝希 ; 藤嶽 暢英*; 清田 佳美*; 飯島 和毅 ; 吉川 英樹
Terashima, Motoki; Nagao, Seiya*; Iwatsuki, Teruki; Fujitake, Nobuhide*; Seida, Yoshimi*; Iijima, Kazuki; Yoshikawa, Hideki
Dissolved humic substances (HSs), i.e., fulvic and humic acids, were isolated from deep groundwater in Horonobe area, Hokkaido, Japan. Eu binding abilities of the groundwater HSs were evaluated by means of three-dimensional fluorescence quenching technique. The conditional binding constants (K'), assuming 1:1 binding, were estimated at pH 5.0 and ionic strength of 0.1. The logK'values of the fulvic and humic acids were comparable with each other regardless of the fluorescence peak positions. Based on the comparisons with the logK' values of HSs from surface environments and commercial product (i.e., Aldrich humic acid), it was found that the Horonobe groundwater HSs had the smallest affinity. The results of Aldrich HA-based comparison also showed that the Horonobe groundwater HSs have the lowest affinity in the bindings of trivalent radionuclides compared to the groundwater HSs isolated from different aquifers. These findings suggest that origin of deep groundwater HSs needs to be considered in assessing the effects of HSs on speciation of radionuclides in deep groundwaters in geological disposal system.