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Water 2017, 9(5), 345;

Using δ15N and δ18O Signatures to Evaluate Nitrate Sources and Transformations in Four Inflowing Rivers, North of Taihu Lake

Division of Groundwater and Soil Environment, School of Environment, Tsinghua University, Beijing 100084, China
State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environment Sciences, Beijing 100012, China
Author to whom correspondence should be addressed.
Academic Editor: Maurizio Barbieri
Received: 28 February 2017 / Revised: 8 May 2017 / Accepted: 8 May 2017 / Published: 17 May 2017
(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)
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Taihu Lake is the third largest freshwater lake in China. Due to rapid economic development and excessive nutrient discharges, there is serious eutrophication in the northern part of the lake. Nitrogen (N) is one of the key factors for eutrophication in Taihu Lake, which mainly comes from the rivers around the lake. Samples from four inflowing rivers were analysed for δ15N and δ18O isotopes in December 2013 to identify the different sources of nitrogen in the northern part of Taihu Lake. The results indicated that the water quality in Taihu Lake was clearly influenced by the water quality of the inflowing rivers and nitrate (NO3-N) was the main component of the soluble inorganic nitrogen in water. The soil organic N represented more than 70% of the total NO3-N loads in the Zhihugang. Domestic sewage was the major NO3-N source in the Liangxi river, with a contribution of greater than 50%. Soil organic N and domestic sewage, with contributions of more than 30% and 35% respectively, were the major NO3-N sources in the Lihe river and Daxigang river. Denitrification might be responsible for the shifting δ15N-NO3 and δ18O-NO3 values in the Daxigang river, and a mixing process may play a major role in N transformations in the Lihe river in winter. The results of this study will be useful as reference values for reducing NO3 pollution in the inflowing rivers in the north of Taihu Lake. View Full-Text
Keywords: nitrate; stable isotopes; nitrate sources; nitrogen transformations; denitrification nitrate; stable isotopes; nitrate sources; nitrogen transformations; denitrification

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Li, D.; Jiang, X.; Zheng, B. Using δ15N and δ18O Signatures to Evaluate Nitrate Sources and Transformations in Four Inflowing Rivers, North of Taihu Lake. Water 2017, 9, 345.

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