2019 Fiscal Year Final Research Report

Elucidation of radiocesium contamination mechanisms in fish revealed by cage experiments conducted in the water bodies near the Fukushima Dai-ichi Nuclear Power Plant

Research Project

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Project/Area Number	17K19279
Research Category	Grant-in-Aid for Challenging Research (Exploratory)
Allocation Type	Multi-year Fund
Research Field	Forestry and Forest Products Science, Applied aquatic science, and related fields
Research Institution	Fukushima University
Principal Investigator	Wada Toshihiro 福島大学, 環境放射能研究所, 准教授 (90505562)
Project Period (FY)	2017-06-30 – 2020-03-31
Keywords	魚類 / 放射性セシウム / 原発事故 / 福島県 / 漁業復興
Outline of Final Research Achievements	The aim of this study is to elucidate the radiocesium contamination mechanisms of fish through multiple approaches such as caging experiments and rearing experiments. Caging experiments of common carp and Japanese eels conducted in a contaminated pond near the Fukushima Dai-ichi Nuclear Power Plant have showed that the Cs concentrations of fish can be increased up to several dozens of Bq/kg through the caging experiments. Japanese dace rearing experiments using Cs-containing pond water revealed that Cs concentrations in muscle tissues were accumulated up to ten times higher than those of rearing water. In contrast, the field surveys in the pond has revealed that Cs concentrations in fish were more than several thousands Bq/kg and concentration factors were averaged around 2400, suggesting strongly that uptake of Cs from food, not from water, would be the primarily Cs contamination route for freshwater fish under the natural environment.
Free Research Field	水産学
Academic Significance and Societal Importance of the Research Achievements	福島原発事故に伴い放出された放射性セシウム（Cs）による淡水魚の放射能汚染の影響は長期化しており、それら汚染メカニズムの解明や将来予測が関連業界や学術界から強く求められている。本研究では、高濃度に汚染された原発周辺における魚類のケージ試験や採集調査、およびCs含有水を用いた飼育試験を行うことで、淡水魚のCsの取込み経路を明らかにした。具体的には、天然環境下では環境水中のCsによる寄与は少なく、餌生物を介したCsの取込みが主な汚染経路であることを明らかにした。本研究成果は、原発周辺水域における魚類のCs汚染経路の解明に寄与し、特に食物連鎖を介したCsの取込みの重要性を示した点で、意義が大きい。