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价潜在的磷资源，本研究旨在确定濑户内海流域地下水和河流排放过程中磷的短期和长期循环。特别是在广岛市的芦田河流域、冈山县的朝日河流域、奈良和大阪府的大和河流域进行了详细的实地调查。在此基础上，我们评估了1)沿海平原和地下水沉积物中的长期（千年尺度）磷循环，2)农业大坝中的短期（数年至数十年）磷循环，以及3)沿海地区磷的再生及其可重复利用资源的潜力。

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.