Nitrogen isotopie technique was used to study the nitrate pollution of four inflowing rivers of Lake Chaohu in different seasons. Our results showed thai River Shiwulihe was the most polluted river, while River Shuangqiaohe as the least polluted one. Nitrogen Stable isolopie values dwnonstrat that nitrate sources differ in various seasons for those four rivers. The dominate pollution sources of nitrate for River Shiwulihe and River Nanfeihe are human sewage and industry discharge. In the case of River Paihe, nitrate is mainly derived from industry discharge in winter, which is originated from agriculture and rainfall in spring and summer, respectively, tor River Shuangqiaohe, nitrate contamination is mainly caused by agriculture in winter and spring, but is influenced by rainfall in summer. In addition, our results imply that ammonium is the main nitrogen pollution compound in those four rivers, and δ15 NH4+ value should be detected for the identification of ammonium sources in further study.%采用氮稳定同位素技术对巢湖四条主要污染输入河流(南淝河、十五里河、派河和双桥河)的氮污染状况和硝态氮来源进行研究结果表明,巢湖四条入湖河流氮污染最严重的是十五里河.其次是南淝河和派河,双桥河的污染相对较轻.硝态氮的稳定同位素分析结果表明,巢湖四条入湖河流的硝态氮污染物在季节上受到不同因子的影响.十五里河和南淝河的硝态氮污染主要来源于城市生活污水和工业废水:派河的硝态氮污染在冬季主要来源于工业废水,春季来源于农业面源,而在夏季主要受到雨水的影响；双桥河的硝态氮污染冬、春季主要来源于农业面源,夏季主要受雨水的影响.此外本研究结果还表明巢湖四条主要入湖河流的氮污染源主要为铵态氮,因此今后要对铵态氮的来源进行同位素示踪.
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