| 研究課題/領域番号 |
18H03389
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| 研究機関 | 福島大学 |
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研究代表者 |
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| 研究分担者 |
難波 謙二 福島大学, 共生システム理工学類, 教授 (70242162)
塚田 祥文 福島大学, 環境放射能研究所, 教授 (50715498)
高橋 隆行 福島大学, 共生システム理工学類, 教授 (70197151)
高瀬 つぎ子 福島大学, 環境放射能研究所, 特任准教授 (10466641)
和田 敏裕 福島大学, 環境放射能研究所, 准教授 (90505562)
脇山 義史 福島大学, 環境放射能研究所, 講師 (40594792)
Zheleznyak Mark 福島大学, 環境放射能研究所, 特任教授 (90745712)
RAHMAN Ismail 福島大学, 環境放射能研究所, 准教授 (60773067)
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| 研究期間 (年度) |
2018-04-01 – 2021-03-31
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| キーワード | Fukushima / Chernobyl / radiocesium / rivers / distribution / transport / speciation / migration |
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| 研究実績の概要 |
Water samples have been collected for dissolved and particulate r-Cs at 8 sites of Abukuma River, 3 sites of Niida River, 3 sites of Maeda River, as well as on two dam reservoirs and four irrigation ponds in Okuma town (monthly sampling). In irrigation ponds r-Cs showed a persistent behavior and was characterized by regular seasonal variations: the r-Cs concentrations tend to grow in the summer and decrease in the winter. Similar behavior of r-Cs was observed in Chernobyl cooling pond over 32 years after the accident. Speciation analysis for Okuma ponds showed much high. It has been shown that the dynamics of radionuclides in the surface runoff and rivers is initially governed by their fixation on mineral particles, while later mainly by changes of the radionuclide activity concentration in the topsoil layer. Several methodologies to collect water samples and separate particulate and dissolved fractions have been used: in situ filtration by original “Midia” system and IER adopted in situ filtration system , as well as laboratory setups. All applied methodologies showed comparable results for all rivers under study. For all rivers, reservoirs and ponds higher values of distribution coefficient between particulate and dissolved r-Cs have been confirmed, as compared with water bodies in Chernobyl contaminated area. All rivers demonstrated higher r-Cs activity concentrations for river mouth as compared with upstream sections. It was explained by the change of river water hydrochemistry from upstream to mouth, specifically a substantial increase of K+ concentration.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
The research is progressing in accordance with the Plan. All permissions for sampling and observations were processed and received in time well before the fieldwork. Access to FDNPP exclusion zone was for fieldwork was provided timely. All necessary equipment and materials were purchased well before the field and laboratory work. Visiting researcher (V. Kanivets from Kiev, Ukraine) was invited to apply in situ water sampling and filtration in the field. Institute of Environmental Radioactivity (IER) has necessary facilities available to carry out planned research. Management of IER and Fukushima University provided continuous support to the Project performance. Participants of the Project held three coordination meetings to plan in details activity and to distribute responsibility among participants. Progress and results of the Project were presented for IER Seminar and IER Fukushima University Annual Symposium.
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| 今後の研究の推進方策 |
Bottom sediments will be collected in Ogaki Dam reservoir (Ukedo River), Yokokawa Dam reservoir (Ota River), Sakashita Dam (Kuma River) reservoir and Shinobu Dam reservoir (Abukuma River) by innovative technique being developed at IER using underwater robot and by conventional technique. Fish will be collected by conventional techniques using gill nets. On the basis of bottom sediments r-Cs vertical distribution in deep accumulating areas of reservoirs dynamics of particulate and dissolved r-Cs from 2011 to 2019 will be reconstructed. R-Cs dynamics in irrigation ponds of Okuma town (Suzuuchi, Funasawa, Inkyozaka and kashiramori) for 2014-2019 will be compared with lakes in Chernobyl exclusion zone Glubokoe and Azbuchin as well as lake Vorsee (Germany) and Svyatoe (Russia). Influence of vertical migration of r-Cs in soils on river catchment on particulate and dissolved r-Cs activity concentrations in river water will be studied. The role of salinity in remobilization of r-Cs from sediments in mouth areas of the rivers Abukuma, Niida and Maeda will be studied. The remobilization of r-Cs will be quantified through concentrations of r-Cs competitive cations such as potassium and ammonium. 32-years data after the Chernobyl accident will serve as a basis for prediction of fate and transport Fukushima-derived r-Cs. Dynamics of r-Cs both in Fukushima and Chernobyl will be modelled and predicted using analytical, empirical, semi-empirical and numerical models (MOIRA, COASTOX and TH REETOX) integrated in the Hydrological Dispersion module of EC RODOS system.
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