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研究报告

Analyses of sources and transformation of nitrogen as a contaminant in the river and lake water in the western region of the Taihu Lake basin

摘要：通过2014年枯水、丰水两期监测,综合分析了太湖西部入湖河流与湖区水体及其沉积物的无机氮形态与同位素特征,并利用δ¹⁵N识别了太湖西部上游区氮污染来源及转化途径的生物化学作用机制.结果表明:NO₃^--N与NH₄⁺-N为研究区域入湖河流无机氮的主要形态,而NO₃^--N为西部湖区水体无机氮的主要形态;δ¹⁵N-NO₃^-的数值范围揭示了西部入湖河流在枯水季NO₃^--N主要来源于农用化肥,有少量矿化土壤有机氮,而丰水季则以生活污水为主,有少量矿化土壤有机氮及农用化肥;δ¹⁵N-NH₄⁺的数值范围说明了生活污水是河流水体NH₄⁺-N的主要来源;通过水体及沉积物样品NO₃^--N、NH₄⁺-N、δ¹⁵N-NO₃^-、δ¹⁵N-NH₄⁺的协同分析可知,湖区氮的赋存形态主要受湖区水体硝化作用及沉积物内反硝化作用的影响.

Abstract：The water and sediments from the river and lake in the western region of the Taihu Lake basin were sampled during the dry and wet season in 2014. The forms of inorganic nitrogen in the samples were analyzed, and the ratio δ¹⁵N was used to identify the sources of nitrogen pollution and the biochemical mechanism of nitrogen cycle in the region. The results showed that:1 NO₃^--N and NH₄⁺-N were the main forms of inorganic nitrogen in the rivers entering the lake, while NO₃^--N was the main form of inorganic nitrogen in the lake water. 2During dry seasons, NO₃^--N in the rivers were mainly from fertilizers and, to a much less extent, from mineralized soil organic nitrogen according to the δ¹⁵N-NO₃^- values. while during wet seasons, N came from sewage and, to a much less extend, from mineralized soil organic nitrogen and fertilizers. 3Sewage was the major source of NH₄⁺-N in the rivers according to the range of the δ¹⁵N-NH₄⁺ values. 4The occurrence of nitrogen in the lake water was mainly affected by nitrification of the lake water and denitrification of the sediments based on combined analyses of NO₃^--N, NH₄⁺-N, δ¹⁵N-NO₃^-, and δ¹⁵N-NH₄⁺ of the water and sediment samples.

Key words：nitrogen isotope identification of nitrogen pollution source migration and transformation the river and lake water in the western region of the Taihu Lake basin