Determination of phosphorus cycles with groundwater and river discharge processes for evaluating the resource potential of them in Seto Inland Sea Watersheds

为了在流域尺度上评估潜在的磷资源，本研究的目的是确定短期和长期的磷循环与地下水和河流排放过程中的濑户内海流域。特别是对广岛县芦田川、冈山县朝日川、奈良县和大坂县大和川流域进行了详细的实地调查。根据研究结果，我们评估了1）长期（千年尺度）的磷在沉积物中的沿海平原和地下水，2）短期（几年到几十年）的磷在一个农业大坝的循环，3）磷在沿海地区的再生和其潜在的可再利用资源。

In order to evaluate the potential phosphorus resource on the watershed scale, this research aimed to determine the short to and long terms of phosphorus cycles with groundwater and river discharge processes in Seto Inland Sea watersheds. Especially, we conducted the detailed field investigations in watersheds of Ashida river of Hiroshima Prefecture, Asahi river of Okayama Prefecture and Yamato river of Nara and Osaka Prefectures. Based on the results, we evaluated 1) long term(millennial-scale) phosphorus cycles in the sediment of coastal plain and the groundwater, 2) short term(years to decades) phosphorus cycles in an agricultural dam, and 3) reproduction of phosphorus in the coastal area and its potential for reusable resource.