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Yamaguchi, Akiko; Okumura, Masahiko; Takahashi, Yoshio*
no journal, ,
no abstracts in English
Kikuchi, Ryosuke*; Fujimura, Tatsuya*; Sato, Tsutomu*; Otake, Tsubasa*; Otomo, Yoko*; Goto, Takahiro*; Suzuki, Satoru*; Taniguchi, Naoki; Suzuki, Hiroyuki*
no journal, ,
Francisco, P. C. M.; Shiwaku, Hideaki; Ishidera, Takamitsu; Tachi, Yukio
no journal, ,
The long-lived fission product Se-79 is a significant contributor to predicted radioactivity in geological repositories long after their closure. One possible retardation in repositories is by incorporation into Fe-sulfides like pyrite (FeS2). In this study, we clarify the role of polysulfides in the incorporation of Se into pyrite. Polysulfides are intermediate-oxidation sulfide species that are likely produced by diagenetic and microbial processes in repository host rocks. The present results show that reaction of Se(-II) with polysulfides resulted in the initial formation of elemental selenium. Aging at anoxic conditions led to the incorporation of Se into pyrite. These results highlight the role of polysulfides in retaining Se. We also investigate the effects of aging in air to determine the effects of changes in the redox conditions. The results show that oxidation did not affect Se retention.
U/
U activity ratios from deep groundwater in siliceous aquiferKuribayashi, Chika*; Miyakawa, Kazuya; Ito, Akane*; Tanimizu, Masaharu*
no journal, ,
no abstracts in English
Takahashi, Yoshio*; Yamaguchi, Akiko; Yomogida, Takumi
no journal, ,
Developments in spectroscopy over the past 25 years have provided detailed information on trace elements in environmental samples. X-ray absorption fine structure (XAFS) techniques have been particularly useful in understanding redox states and local structure, and newer techniques have been developed. These techniques have enabled elemental comparisons and systematic understanding based on the periodic table, and have allowed a better understanding of the geochemical behavior of almost all elements in the periodic table. These developments and findings will be presented.