No.188 研究課題 / Project

窒素安定同位体比法を用いた多摩川の窒素汚染と浄化作用に関する研究Nitrogen pollution and purification function of Tamagawa River, by nitrogen stable isotope ratio analysis

学術研究
Academic Research
No.188
代表研究者
Principal Investigator
熊澤 喜久雄
Kikuo Kumazawa
所属(採択当時)
Affiliation
東京農業大学教授
Tokyo University of Agriculture
研究内容要約
Research Summary
多摩川本流及び主要な支流について、各種イオン濃度を調べ、特に窒素化合物に ついて、それらの濃度及び重窒素自然存在比(δ15N)を測定し、窒素汚染源や脱窒 などによる窒素浄化の程度を推定した。その結果(1)多摩川本流の源流近くでは硝 酸態窒素濃度は0.02mgL-1程度である。(2)上流部では硝酸態窒素濃度は0.10~ 0.35mgL-1、δ15N値は+1.05~+1.14‰であったが、人為的汚染が加わるにつれ て、両者ともにその値が上昇し、中流部ではそれぞれ0.44~1.61mgL-1及び +5.2~+9.2‰、下流部では3.42~6.64mgL-1、+10.l~+12.7‰ にもなっていた。 (3)丹波川、日原川、南秋川上流、北浅川上流域の水質は良好であったが、玉川取 水堰より下流では、家庭排水由来の窒素により次第に汚染してくる。(4)流域の湧 水には硝酸態窒素濃度の高いものが多く、土壌由来窒素や家庭排水などによる地下 水汚染が起きていると推定された。(5)仙川、南浅川等の流域からの家庭排水は下 水処理排水とともに多摩川の主な窒素汚染源となっている。

This research examined concentrations of various ions in the Tamagawa River and its major tributaries. Also, in order to understand the sources of nitrogen pollution and the levels of nitrogen purification, thanks to denitrification, we measured the concentrations of nitrogen compounds and heavy nitrogen ratio (d15N). Results were as follows:

(1) Nitrate nitrogen concentrations were about 0.02 mgL-1 around the headwaters of the Tamagawa River

(2) Nitrate nitrogen concentrations ranged from 0.10 to 0.35 mgL-1 in the upper Tamagawa river basin, and d15N values varied from +1.05 to +1.14 ‰. However, as affected by anthropogenic pollution farther downstream, both values increased as follows: from 0.44 to 1.61 mgL-1 and from +5.2 to +9.2 ‰, respectively, in the middle basin; from 3.42 to 6.64 mgL-1 and from +10.1 to +12.7 ‰, respectively, in the lower basin

(3) Water quality was good in the Tama and Nippara rivers, and in the upper basin of the Minami Asagawa and Kita Asagawa rivers. However, pollution became severe downstream of the Tamagawa Intake Weir, due to nitrogen originating from domestic waste water.

(4) Much of the spring water in the basin contained high levels of nitrate nitrogen. It was believed that groundwater was polluted by soil-originating nitrogen and domestic waste water.

(5) Domestic waste water, as well as treated waste water, from the Sengawa River and the Minami Asagawa River was the major source of nitrogen pollution.
共同研究者
Collaborators
山本洋司、加藤 茂、朴 光来、田村幸美

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