Characteristics of Urban Non-Point Source Pollution in Suzhou City

Urban non-point source (NPS) pollution of Suzhou City in different land use was investigated from Nov. 2006 to Sep. 2008 in this paper. The results show that pollutants concentrations were very variable and dispersed for different sampling sites. The median values of Event Mean Concentrations (EMC) of COD, SS, NH₃-N, TN and TP were 119-225, 93-188, 2.30-11.77, 6.35-19.56 and 0.8-2.7 mg/L, varied in different land use category, the corresponding pollution loads were 26112, 26721, 895, 1921 and 242 ton respectively, those were 0.4-1.7 times of the sanitary wastewater discharged into the watershed. It indicates the urban NPS pollution is the major factor for the urban river quality degradation. No significant strong first flush occurred in the studied watersheds for all the events. Generally, the first flush effect is weak in the storm runoff in Suzhou urban area.