Nitrogen pollution status of various types of passing-by water bodies in upper reaches of Taihu Lake
太湖上游不同类型过境水氮素污染状况

With the aid of Global Positioning System(GPS),this paper investigated the present nitrogen pollution status of passing-by water bodies in the agricultural area,rural residential area,fishpond area,and animal farming area of Yixing in the upper reaches of Taihu Lake in spring,summer,autumn and winter.The seasonal variations of the nitrogen concentration in the water bodies were analyzed,and the 15N natural abundance in the water bodies was compared.The results showed that anthropogenic activities had intense effects on the nitrogen pollution,and various agricultural and anthropogenic activities had different nitrogen pollution characters.The passing-by water bodies in agricultural area were more easily polluted by NO3--N than by NH4 -N,and the NH4 -N concentration in passing-by water bodies was higher in rural residential area than in agricultural area due to the domestic sewage discharge.The passing-by water bodies in animal farming area was often heavily polluted by NH4 -N.Fishponds had the least nitrogen pollution,compared to other passing-by water bodies,and the main pollutant was organic nitrogen.The nitrogen pollution of the passing-by water bodies was also affected by the seasonal evolvement of environment,with the lowest nitrogen concentration in summer and the highest one in winter.Farmland fertilization was the main source of the nitrogen pollution in Taihu Lake,and domestic sewage and animal excreta were also the important nitrogen pollution sources when the water level was high.