Abstract: From November of 2007 to October of 2008, stationary observation was performed of nitrogen (N) and phosphorus (P) pollution of rivers and fish ponds in Xinzhuang Town, Changshu, to explore variation of N and P concentrations in the waterbodies and sources of the pollutants. Results show that in the river water, the mean concentration of inorganic N, total N, soluble P and total P was 2.07,2.31,0.30 and 0.53 mg·L^-1, respectively, indicating that the river was severely polluted. In the rivers and fish ponds, inorganic N dominated the pollutant N accounting for 89.6% and 72.7%, respectively and soluble phosphorus did the pollutant P, accounting for 73.6% and 71.1%, respectively. Generally, the mean concentrations of nitrate N, inorganic N and total N in the rivers and fish ponds showed a similar variation trend, while the mean concentrations of phosphate, soluble P and total P differed in variation between the rivers and fish ponds. Nitrogen and phosphorus pollution in the rivers came mainly from domestic sewage and pig farms waste water, while nitrogen and phosphorus pollution in the fish ponds from application of baits and fertilizers,and atmospheric nitrogen deposition was also an important contributor to nitrogen pollution of the waterbodies.

Key words: nitrogen, phosphorus, river, fish pond, Changshu