横川ダム流域における溶存態放射性セシウムの挙動に関する研究(JAEA-NIES共同調査)

Behaviour of dissolved radiocesium within a Yokokawa dam reservoir basin (Research collaboration with JAEA and NIES)

佐久間 一幸   ; 辻 英樹*

Sakuma, Kazuyuki; Tsuji, Hideki*

福島県の横川ダム流域における溶存態の放射性セシウム(Cs)の動きに注目し、(1)ダム湖における溶存態Cs濃度の水平分布、(2)プランクトンへの濃縮、(3)ダム湖上流域での発生源等の調査、および(4)解析を行った。溶存態のCs濃度はダム流入水・放流水ともに減少傾向であり、その発生源は有機物からの寄与が大きいことが確認された。さらに平水時における溶存態Cs濃度の変化を数値モデルを用いて再現した。

We focus on a behavior of dissolved radiocesium within Yokokawa dam reservoir in Fukushima prefecture. (1) Horizontal distribution of dissolved Cs concentration in reservoir water, (2) Cs concentration of a plankton, (3) Investigation for sources of dissolved Cs from an upstream catchment of the dam reservoir, (4) Simulation for dissolved Cs discharge from the upstream catchment of the dam reservoir were studied. These indicated that dissolved Cs concentration in water at dam inlet and outlet were decreasing and an organic matter is one of the dissolved Cs source in forested catchment. Additionally we developed a numerical model to simulate dissolved Cs concentration at the catchment outlet, which reasonably reproduced a observation data under base flow periods.