2021 Fiscal Year Final Research Report
In-situ determination of denitrification, assimilation, and nitrification rates in streams using triple oxygen isotopes of dissolved nitrate as tracer
| Project/Area Number |
19H04254
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Review Section |
Basic Section 63010:Environmental dynamic analysis-related
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| Research Institution | Nagoya University |
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Principal Investigator |
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | 河川 / 脱窒速度 / 硝化速度 / 同化速度 / 三酸素同位体組成 / 大気硝酸濃度 |
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| Outline of Final Research Achievements |
In this study, we propose a new tracer called “atmospheric nitrate concentration”, which can be calculated from both concentration and triple oxygen isotopic composition of dissolved nitrate in river water, to determine the removal rate of nitrate (sum of denitrification rate and assimilation rate) in the river environments. We determine the in-situ denitrification, assimilation, and nitrification rates in the river water individually by tracing the atmospheric nitrate concentration together with total nitrate concentration. The results were compared with the denitrification / assimilation rate obtained by the conventional culture method. The new method is an epoch-making method that can quantify the denitrification rate of the entire river environment including the riverbed in the natural state without adding or culturing an artificial tracer.
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| Free Research Field |
生物地球化学
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| Academic Significance and Societal Importance of the Research Achievements |
本研究の目的は、河川環境下における脱窒・硝化・同化速度の時空間変化を正確に実測する手法を開発することである。従来の河川環境における脱窒速度の推定は、生態系モデルを使った研究例や、アセチレン阻害法や人工同位体トレーサー法といった培養法を使った研究例が多く、実際の河川環境で自然の状態のまま脱窒速度を実測する手法は無かった。本研究が提案する新手法は、天然トレーサーを使っており、自然の状態のまま河床を含めた河川環境全体の窒素循環速度を定量できる。この新手法が確立することで、河川環境の窒素浄化能力やその規定因子に対する知見が深まり、関連する環境学、工学、農学、水産学など多くの分野の発展に貢献する。
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