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Yokoyama, Tatsunori; Kokubu, Yoko; Mitsuguchi, Takehiro*; Murakami, Hiroaki; Hirata, Takafumi*; Sakata, Shuhei*; Danhara, Toru*; Iwano, Hideki*; Maruyama, Seiji*; Chang, Q.*; et al.
no journal, ,
no abstracts in English
Miyakawa, Kazuya; Sasamoto, Hiroshi; Murakami, Hiroaki
no journal, ,
no abstracts in English
Yokoyama, Tatsunori; Misawa, Keiji*; Yoneda, Shigekazu*
no journal, ,
no abstracts in English
Cs concentration in river water following the Fukushima nuclear accident in FY 2015-2017Nakanishi, Takahiro; Katayose, Yuji*; Osotsuka, Koji*; Haginoya, Takumi*; Matsumoto, Takumi*
no journal, ,
A large amount of radiocesium emitted from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident was deposited in terrestrial areas. It is therefore important to determine the quantity of radiocesium transported from these areas by hydrological processes to predict the future contamination status and propose effective countermeasures to reduce exposure. In this paper, we report the trend of the radiocesium concentration in 2 rivers nearby FDNPP and discuss the environmental factors on behavior of radiocesium.
Watanabe, Yusuke; Fukuda, Kenji; Murakami, Hiroaki; Iwatsuki, Teruki; Suzuki, Yohei*
no journal, ,
Oxic condition may spread into the deep groundwater by penetrating of shallow oxic groundwater during construction and operation of geological repository for the geological disposal of nuclear waste. On the other hand, microbial activities living in deep underground such as sulfate reducing bacteria could keep the redox condition in groundwater reductive by the reduction of sulfate ion to hydrogen sulfide. In this study, in situ incubation experiment for sulfate reducing bacteria was conducted to observe its redox buffering capacity. Results showed that reducing condition was made by activities of sulfate reducing bacteria in the groundwater.
Sasaki, Yoshito; Niizato, Tadafumi; Mitachi, Katsuaki*
no journal, ,
We collected the tree sap in the Japanese cedar, and clarified the concentration of the dissolved radiocesium contained in the sap. It was shown that the amount of dissolved radiocesium in sap in each part was about 30 to 50% of the total amount of radiocesium at each part.
Miyajima, Yusuke*; Saito, Ayaka*; Kagi, Hiroyuki*; Yokoyama, Tatsunori; Hirata, Takafumi*
no journal, ,
no abstracts in English
Yoshimura, Kazuya; Kanaizuka, Seiichi*
no journal, ,
no abstracts in English
Be in bed-sediments of Ado and Yasu rivers flowing into Lake BiwaFujisawa, Jumpei*; Minami, Masayo*; Kokubu, Yoko
no journal, ,
To investigate grain size dependency on concentration of meteoric Be extracted from river bed-sediment, we analyzed the Be in bed-sediments of Yasu and Ado rivers flowing into Lake Biwa, Shiga Prefecture. Each of 5 grain size fractions was sequentially leached to extract Ex (Exchangeable), Am-Ox (amorphous oxy-hydroxide) and X-Ox (crystalline oxy-hydroxide) phases, respectively, and the Be concentrations of the leachates were measured. Most meteoric Be was located in the Am-Ox and X-Ox phases. The concentrations of bulk and extracted fractions decreased with increasing grain size. Furthermore, the bed-sediments from upper stream showed higher concentration than those from downstream, and this tendency was stronger in Yasu river than in Ado river. The difference between Yasu and Ado river sediments could be due to lower pH of water in Yasu river than in Ado river, that is, due to more partitioning of Be into water relative to sediment particles in Yasu river.
Shimoyama, Iwao; Kogure, Toshihiro*; Okumura, Taiga*; Baba, Yuji
no journal, ,
More than 99% of radioactive Cs can be removed from soil by heat treatment at more than 1000
C, however, its high cost inhibits application of this method. In this work, we attempted heat treatment with four kinds of chloride reagents under low-pressure condition to decrease processing temperature. Each reagent was added to contaminated soil and heat treatment was applied in air and under low-pressure conditions for two hours. In the case of CaCl
, the difference in decontamination ratio was small for different pressure conditions and decontamination ratio reached to 95% at 790C. On the other hand, MgCl, NaCl, and KCl had higher decontamination ratios under low-pressure conditions than in air. When MgCl was added, decomposition and phase transformation of biotite in soil was facilitated under low-pressure conditions, and decontamination ratios at 695C were 40 and 90% in air and under low-pressure conditions, respectively. In the cases of NaCl and KCl, biotite remained after the heat treatments and Cs was removed through ion exchange. When NaCl was added, decontamination ratios at 790C were 15 and 94% in air and under low-pressure conditions, respectively. Based on these results, we propose heat treatment with sea water salt as a reactant.
Tokunaga, Kohei; Takahashi, Yoshio*; Kozai, Naofumi
no journal, ,
In the present study, we explore a new application of barite (BaSO
) as a sequestering phase for radioactive nuclides from aqueous solutions. Barite is a common phase in many geological environments, and it can be used to remove toxic and/or radioactive elements from aqueous solutions, but it has not been widely used in environmental studies. This study describes the mechanisms of SeO
, SeO, IO
, and Sr
distribution between barite and water, thus providing a good estimate of its ability to effectively remove these ions from aqueous solutions (more than 80%) using the optimized experimental parameters examined here.
Osawa, Takahito
no journal, ,
no abstracts in English
Okumura, Masahiko; Nakamura, Hiroki; Machida, Masahiko
no journal, ,
no abstracts in English