[M-AG34] ラジオアイソトープ移行：福島原発事故環境動態研究の新展開

[MAG34-02] 森林源頭部流域からのCs-137移行フラックスに対する浅層地下水流出の影響

*加藤 弘亮¹、庭野 佑真¹、恩田 裕一¹ (1.筑波大学放射線・アイソトープ地球システム研究センター)

キーワード：福島第一原子力発電所事故、セシウム137、森林流域、浅層地下水

In the aftermath of the Fukushima Daiichi Nuclear Power Plant disaster, radiocesium (Cs-137) dispersion through forest ecosystems into aquatic systems has raised environmental concerns. While prior investigations have delineated the augmentation of Cs-137 in surface waters, attributing this to the deposited litter leaching, the role of groundwater runoff on Cs-137 discharge remains underexplored. This research aims to elucidate the role of shallow groundwater, characterized by diverse residence times and pathways on forested slopes, in modulating Cs-137 concentrations within surface waters. Employing detailed hydrological monitoring at a forest hillslope, we discerned elevated Cs-137 levels in shallow groundwater compared to adjacent surface waters. Notably, surface water Cs-137 concentrations surged in conjunction with rainfall events, accompanied by pronounced groundwater flow toward river channels. A significant correlation between the groundwater hydraulic gradient and surface water flow rate was identified, underscoring the pivotal contribution of shallow groundwater discharge to both the enhanced flow and Cs-137 levels in surface waters. This study quantifies shallow groundwater's impact on Cs-137 surface water concentrations, leveraging detailed hydrological data and Cs-137 measurements. Our findings contribute to a deeper understanding of radioactive contaminant dynamics in forested watersheds, highlighting the need for integrated water management strategies post-nuclear accidents.