中文摘要：

利用GPS定位的方法在丰水期和枯水期对常熟地区境内12条河流和3个湖荡水体氮磷污染现状进行了调查研究，对常熟地区主要河湖地表水中不同形态氮浓度的季节性变化特征进行了初步探讨。根据地表水中不同形态氮的浓度及总磷、溶解磷的浓度。结合15N示踪法和大型原状土柱渗漏池试验进一步补充探明了对该地区河湖水体中的氮磷污染来源。研究发现，该地区河、湖水体氮磷污染已相当严重，现阶段氮磷污染源主要来自城镇生活污水、农村人畜排泄物，在此基础上提出了缓解该地区水体氮磷污染的相应对策。

英文摘要：

With the aid of the Global Positioning System （GPS）, present status of nitrogen and phosphorus pollution in water bodies in the high and low water periods of twelve rivers and three lakes in Changshu region was investigated, and seasonal variations of concentrations of nitrogen in different forms in the surface layers of the water bodies were researched. Based on nitrogen concentrations of different forms, total phosphorus and soluble phosphorus in the surface water, nitrogen and phosphorus pollution sources were further explored by means of a field undisturbed tension-free monolith lysimeter（1 m^2 in area and 1 m in depth）in combination with the 15N-tracing method. The results show that the water bodies in the region are severely polluted by nitrogen and phosphorus. Nitrogen pollution of the water bodies is not only caused by chemical nitrogen application in the farmland through leaching and runoff of nitrogen, but also by improper handling of domestic sewage and human and animal excreta in the countryside. Atmospheric nitrogen wet deposition （including rainfall and snowfall） could be one of the sources of nitrogen pollution in the water bodies. Besides, some countermeasures are suggested to mitigate nitrogen and phosphorus pollution in the water bodies in this region in light of the local physical circumstances.