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Micheau, C.; Ueda, Yuki; Motokawa, Ryuhei; Bauduin, P.*; Girard, L.*; Diat, O.*
Langmuir, 39(31), p.10965 - 10977, 2023/07
Times Cited Count：0 Percentile：0(Chemistry, Multidisciplinary)Kobayashi, Keita; Yamaguchi, Akiko; Okumura, Masahiko
Applied Clay Science, 228, p.106596_1 - 106596_11, 2022/10
Times Cited Count：6 Percentile：77.65(Chemistry, Physical)no abstracts in English
Nara, Yoshitaka*; Kato, Masaji*; Sato, Tsutomu*; Kono, Masanori*; Sato, Toshinori
Journal of MMIJ, 138(4), p.44 - 50, 2022/04
It is important to understand the long-term migration of radionuclides when considering rock engineering projects such as the geological disposal of radioactive waste. The network of fractures and pores in a rock mass plays a major role in fluid migration as it provides a pathway for fluid flow. The geometry of a network can change due to fracture sealing by some fine-grained materials over long-term periods. In the present study, we use a macro-fractured granite sample to investigate the change of permeability that occurs under the flow of water that includes two different amounts of clay. Findings showed that clay accumulated in a fracture and that the permeability (hydraulic conductivity) of the granite sample decreased over time, which was greater in for the higher clay content. We concluded that the accumulation of clay minerals in the fracture decreased the permeability of the rock. Furthermore, we consider that the filling and closure of fractures in rock is possible under the flow of groundwater that includes clay minerals.
Okumura, Masahiko
Chikyu Kagaku, 55(4), p.110 - 121, 2021/12
no abstracts in English
Okamoto, Yoshihiro; Osugi, Takeshi; Shiwaku, Hideaki; Akabori, Mitsuo*
Insights Concerning the Fukushima Daiichi Nuclear Accident, Vol.4; Endeavors by Scientists, p.285 - 294, 2021/10
The transfer behavior of cesium adsorbed on some clay minerals in aqueous solution was investigated by X-ray absorption fine structure (XAFS) analysis of the Cs K-edge. The sample was prepared by mixing Cs-adsorbed mineral with a different pure clay mineral in water. The XAFS results of the dried mixture powder were compared with those obtained before mixing. It was recognized from the XAFS analysis for three kinds of clay minerals illite, kaolinite and vermiculite, that cesium was transferred from kaolinite to illite and vermiculite, and from illite to vermiculite. It can be concluded that cesium is transferred to and accumulated in vermiculite.
Fukuda, Tatsuya*; Takahashi, Ryo*; Hara, Takuhi*; Ohara, Koji*; Kato, Kazuo*; Matsumura, Daiju; Inaba, Yusuke*; Nakase, Masahiko*; Takeshita, Kenji*
Journal of Nuclear Science and Technology, 58(4), p.399 - 404, 2021/04
Times Cited Count：6 Percentile：60.71(Nuclear Science & Technology)Kimura, Tatsuki*; Kozai, Naofumi; Sakamoto, Fuminori; Fukutani, Satoshi*; Ikegami, Maiko*
Doboku Gakkai Rombunshu, G (Kankyo) (Internet), 76(7), p.III_375 - III_382, 2020/00
no abstracts in English
Yoshigoe, Akitaka
Hoshako Riyo No Tebiki, p.130 - 138, 2019/02
The educational book on next-generation synchrotron radiation usage is partially written. This book is being planned by several professors at Tohoku University. In this book, the contents which have already reported in our recent paper [Appl. Phys. Lett. 112 (2018) 021603.] are mainly written. The future perspective on photoemission electron microscopy using next generation synchrotron radiation and its possibility to analyze environmental samples and insulating functional materials are also described.
Okumura, Masahiko; Kerisit, S.*; Bourg, I. C.*; Lammers, L. N.*; Ikeda, Takashi*; Sassi, M.*; Rosso, K. M.*; Machida, Masahiko
Journal of Environmental Radioactivity, 189, p.135 - 145, 2018/09
Times Cited Count：51 Percentile：87.2(Environmental Sciences)no abstracts in English
Nagasu, Ryosuke*; Tanabe, Daijiro*; Yokotsuka, Satoshi*; Kumazawa, Noriyuki*; Ajiki, Takaya*; Aizawa, Yusuke*; Naganawa, Hirochika; Nagano, Tetsushi; Yanase, Nobuyuki*; Mitamura, Hisayoshi*; et al.
Kankyo Joka Gijutsu, 17(2), p.58 - 61, 2018/03
A new technology to suppress cesium migration from forests has been developed collaboratively by Ibaraki University, Kumagai-gumi Co., Ltd. and its group company, Technos, and JAEA. The new technology utilizes polyelectrolytes (polymers with electric charges) and clay minerals to control Cs migration with the aid of natural forces such as rainfall and rainwater runoff. In Imitate-mura, Fukushima, verification tests of the new technology have been performed and its effect on controlling Cs migration from forests to grass farm adjoining the forests has been proven.
Yoshigoe, Akitaka; Shiwaku, Hideaki; Kobayashi, Toru; Shimoyama, Iwao; Matsumura, Daiju; Tsuji, Takuya; Nishihata, Yasuo; Kogure, Toshihiro*; Okochi, Takuo*; Yasui, Akira*; et al.
Applied Physics Letters, 112(2), p.021603_1 - 021603_5, 2018/01
Times Cited Count：6 Percentile：34.59(Physics, Applied)A synchrotron radiation photoemission electron microscope (SR-PEEM) was applied to demonstrate pinpoint analysis of micrometer-sized weathered biotite clay particles with artificially adsorbed cesium (Cs) atoms. Despite the insulating properties of the clay, we observed the spatial distributions of constituent elements (Si, Al, Cs, Mg, Fe) without charging issues. We found that Cs atoms were likely to be adsorbed evenly over the entire particle. Spatially-resolved X-ray absorption spectra (XAS) of the Cs M
-edge region showed Cs to be present in a monocation state (Cs
). Further pinpoint XAS measurements were also performed at the Fe L
-edge to determine the chemical valence of the Fe atoms. Our results demonstrate the utility of SR-PEEM as a tool for spatially-resolved chemical analyses of various environmental substances, which is not limited by the poor conductivity of samples.
Sassi, M.*; Rosso, K. M.*; Okumura, Masahiko; Machida, Masahiko
Clays and Clay Minerals, 65(5), p.371 - 375, 2017/11
Times Cited Count：2 Percentile：79.17(Chemistry, Physical)no abstracts in English
Araki, Yuki*; Sato, Hisao*; Okumura, Masahiko; Onishi, Hiroshi*
Surface Science, 665, p.32 - 36, 2017/11
Times Cited Count：11 Percentile：48.83(Chemistry, Physical)no abstracts in English
Sassi, M.*; Okumura, Masahiko; Machida, Masahiko; Rosso, K. M.*
Physical Chemistry Chemical Physics, 19(39), p.27007 - 27014, 2017/10
Times Cited Count：4 Percentile：17(Chemistry, Physical)no abstracts in English
Okumura, Masahiko; Sassi, M.*; Rosso, K. M.*; Machida, Masahiko
AIP Advances (Internet), 7(5), p.055211_1 - 055211_9, 2017/05
Times Cited Count：6 Percentile：29.59(Nanoscience & Nanotechnology)no abstracts in English
Lammers, L.*; Bourg, I. C.*; Okumura, Masahiko; Kolluri, K.*; Sposito, G.*; Machida, Masahiko
Journal of Colloid and Interface Science, 490, p.608 - 620, 2017/03
Times Cited Count：107 Percentile：93.33(Chemistry, Physical)no abstracts in English
Kerisit, S.*; Okumura, Masahiko; Rosso, K. M.*; Machida, Masahiko
Clays and Clay Minerals, 64(4), p.389 - 400, 2016/08
Times Cited Count：29 Percentile：74.44(Chemistry, Physical)no abstracts in English
Cs in forest surface environments; Application to a contaminated forest site near Fukushima and assessment of potential impacts of soil organic matter interactionsOta, Masakazu; Nagai, Haruyasu; Koarashi, Jun
Science of the Total Environment, 551-552, p.590 - 604, 2016/05
Times Cited Count：33 Percentile：72.19(Environmental Sciences)A model for Cs transfer in forest was developed to assess behavior of Fukushima-derived Cs. The model simulation well reproduced observed 3 year migration of Cs in organic layer and mineral soil. Long-term predictions indicated that more than 90% of the deposited Cs remains in the top 5 cm soil till 30 years, suggesting that forest acts as a long-term reservoir of Cs with limited loss via groundwater pathway. Impacts of soil organic matter (SOM) on Cs dynamics were investigated by modifying parameters of Cs turnover. The results showed that SOM-induced reduction of Cs adsorption, slower fixation of Cs by clay and enhanced mobilization of the fixed Cs elevate soil-to-plant transfer of Cs by increasing fraction of dissolved Cs. A substantial proportion (27% 
73%) of Cs in these soils was delivered to horizons deeper than 5 cm decades later. These results suggested that SOM significantly influences behavior of Cs over long-term.
Sassi, M.*; Rosso, K. M.*; Okumura, Masahiko; Machida, Masahiko
Clays and Clay Minerals, 64(2), p.108 - 114, 2016/04
Times Cited Count：6 Percentile：21(Chemistry, Physical)no abstracts in English
Yaita, Tsuyoshi
Hoshasen To Sangyo, (138), p.13 - 16, 2015/04
no abstracts in English
