[A-HW16] 流域生態系の水及び物質の輸送と循環－源流域から沿岸域まで－

[AHW16-P11] 逐次抽出法を用いた野洲川における懸濁態リンの生物利用可能性とその起源評価

*千代 真照¹、尾坂 兼一²、藤田 健斗¹、永淵 修²、奥田 昇³ (1.滋賀県立大学大学院環境科学研究科、2.滋賀県立大学環境科学部、3.総合地球環境学研究所)

キーワード：懸濁態リン、逐次抽出、生物利用可能性、琵琶湖

It is well known that primary production in Lake Biwa is limited by phosphorus, and that means phosphorus load into Lake Biwa influence on its environment. In general, it is considered that algae in lake use PO₄-P as a phosphorus nutrient, however, it has been revealed that a part of particulate phosphorus (PP) also might be used as nutrient in recent study. It has been reported that the load of PP discharged through river increases during ploughing and irrigating the fields or rainfall event, and most of the annual phosphorus load discharged through river is PP. However, there are a few studies that clarify the sources and bioavailability of fraction of PP discharged through river in Japan. The purpose of this study is to estimate sources of bioavailable fractions of PP discharged through Yasu river into Lake Biwa.
River water samples were collected from 5 sites in Yasu river once or twice a week from April 2015 to May 2015. Drainage from paddy fields were collected from Koka city, where locates in middle part of Yasu river watershed once a month between May and July. Furthermore, river water samples after rainfall event were collected from 10 rivers flowing into Lake Biwa on September 2015. After sampling, we separated several fractions of PP from suspended solids by sequential extraction methods (1M ammonium chloride, 0.11M bicarbonate dithionite, 1M NaOH, 0.5M HCl extraction) in water sample. In this method, PO₄-P is extracted from the particle fraction with high bioavailability in sequence. PO₄-P extracted from the particle fraction was determined by the molybdenum-blue method.