Estimation and Source Apportionment of Agricultural Non-point Source Pollution in Suzhou City, China

The primary source, influence factors and spatial distribution characteristics of agricultural non-point source pollution in Suzhou City(a typical area of the Yangtze River Delta)were analyzed by inventory analysis, equivalent standard load and Nemerow analysis methods of water quality. Results showed that the absolute real emissions of COD, ammonium nitrogen, TN and TP from agricultural non-point source pollution in Suzhou were still greater, which was 171 268.2, 6 510.5, 21 839.3 t·a-1 and 3 335.7 t·a-1, respectively. And the agricultural nonpoint source pollution in Suzhou was combined with production and life sources. In addition, livestock industry was an important source of the emission of COD and total phosphorus, while ammonium nitrogen and total nitrogen were mainly coming from rural life source. However, Taicang City was the most severe area of COD and TP emission, while ammonium nitrogen and TN were mainly discharged from the Suzhou urban area. The mean value of comprehensive water quality index(CWQI)of Suzhou City was 2.6, reaching the moderate pollution level. As for the different zones in Suzhou City, the comprehensive water quality index of Changshu and Taichang all reached serious pollution level; Suzhou urban area and Kunshan were light pollution and Zhangjiagang was moderate pollution, respectively. In contrast, there was no significant relationship between the agricultural non-point source pollution intensity and local agro-forestry economy.