| 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 |
高瀬 つぎ子 福島大学, 環境放射能研究所, 特任准教授 (10466641)
脇山 義史 福島大学, 環境放射能研究所, 講師 (40594792)
塚田 祥文 福島大学, 環境放射能研究所, 教授 (50715498)
RAHMAN Ismail 福島大学, 環境放射能研究所, 准教授 (60773067)
高橋 隆行 福島大学, 共生システム理工学類, 教授 (70197151)
難波 謙二 福島大学, 共生システム理工学類, 教授 (70242162)
和田 敏裕 福島大学, 環境放射能研究所, 准教授 (90505562)
Zheleznyak Mark 福島大学, 環境放射能研究所, 特任教授 (90745712)
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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 / remobilization / fish |
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| 研究実績の概要 |
Bottom sediments have been collected in Ogaki Dam reservoir (Ukedo River), Yokokawa Dam reservoir (Ota River) and Sakashita Dam reservoir (Kuma River) reservoir. Fish was collected in the same water bodies using gill nets. On the basis of bottom sediments r-Cs vertical distribution in deep areas of Ogaki dam reservoir dynamics of particulate and dissolved r-Cs from 2011 to 2019 was reconstructed. Using sediment traps suspended sediments at various depths have been collected in Shinobu dam reservoir (Abukuma River) and at Okuma town ponds Inkyozaka and Funasawa. It was shown that particulate r-Cs has a maximum at the middle of cross-section and r-Cs activity concentration there is about 5 times higher than on the surface and near the bottom. Data on particulate r-Cs from traps were in agreement with r-Cs measurements from water sampling. The role of salinity in remobilization of r-Cs from sediments in mouth areas of the rivers Niida and Maeda was quantified through concentrations of r-Cs competitive cations such as potassium and ammonium. It was found that the general trend of the particulate and dissolved r-Cs activity concentrations in case of Chernobyl could be described by the semi-empirical “diffusional” model. In case of Fukushima the reduction of r-Cs goes faster than predicted by the “diffusional” model. Dynamics of r-Cs both in Fukushima and Chernobyl were 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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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
The research is progressing in accordance with the Plan. Visiting researchers (M. Ivanov from Moscow State University and M. Komissarov from Ufa Institute of Biology, Russia) were invited to participate in field and laboratory research on the Project. Institute of Environmental Radioactivity (IER) has necessary facilities available to carry out planned research. Participants of the Project held coordination meetings and seminars to plan in details activity, to distribute responsibility among participants and to discuss preliminary results. Bottom sediment cores were collected in dam reservoir under study. Fish was collected by conventional techniques using gill nets. On the basis of bottom sediments r-Cs vertical distribution in deep accumulating area of Ogaki dam reservoir dynamics of particulate and dissolved r-Cs from 2011 to 2019 was reconstructed. R-Cs dynamics in irrigation ponds of Okuma town for 2014-2019 was compared with lakes in Chernobyl exclusion zone Glubokoe and Azbuchin. Semi-empirical model of r-Cs dynamics in rivers and ponds was developed and applied for rivers and ponds under study in Fukushima. The role of salinity in remobilization of r-Cs from sediments in mouth areas of the rivers Niida and Maeda was identified, studied and quantified through concentrations of r-Cs competitive cations such as potassium and ammonium. 32-years data after the Chernobyl accident have been collected and used as a basis for prediction of fate and transport Fukushima-derived r-Cs. A number of articles and chapters monograph were published based on the Project results.
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| 今後の研究の推進方策 |
Collection of water, bottom and suspended sediments, fish will be continued and more statistical data will be obtained on reconstructed dynamics of particulate and dissolved r-Cs from 2011 to 2020. Data on long-term dynamics of r-Cs in rivers and lakes in Chernobyl exclusion zone will be collected and compared with results obtained for Fukushima rivers, lakes and reservoirs. Influence of climate and geomorphological as well as r-Cs speciation in fallout on long-term behavior in the environment will be analyzed. Special attention will be given to dynamics of dissolved and particulate r-Cs during typhoon's flooding. Artificial grass mats will be installed on Abukuma River floodplain sites to investigate sediment and r-Cs accumulation and loss. Sediment cores will be also collected on the same sites. Size distribution of suspended and bottom sediments will be studied as well as r-Cs distribution among sediment size fractions. Consecutive filtration with filters of various pore size will be also used to determine r-Cs distribution among suspended matter size fraction. R-Cs concentration ratio will be determined for fish and its dependence on hydrochemical characteristics will be studied. Modelling of r-Cs dynamics r-Cs both in Fukushima and Chernobyl will be continued using analytical, empirical, semi-empirical and numerical models (MOIRA, COASTOX and TH REETOX) integrated in the Hydrological Dispersion module of EC RODOS system. The results will be summarized and generalized to be published in monograph by SPRINGER and international scientific journals.
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