Analysis on characteristics of urban non-point source pollution

The type, source and harm of pollutants of urban non-point source pollution and its influence on the receiving water are analyzed. The results of former research on characteristics of urban non-point source pollution are summarized systemically. It is concluded that the main pollutants of urban surface runoff are suspended solid, the concentration of which is distinctively higher than that in sewage. There is no difference in the concentrations of heavy metals and hydrocarbons between urban runoff and untreated sewage. The concentrations of COD, BOD_5, total coli-group, total nitrogen, and total phosphorus are lower than those in urban sewage. Pollution of urban runoff in shopping center is most serious among all types of urban land use. Metals in urban runoff mainly come from roof runoff, and hydrocarbons and lead often adhere to the particulate matters. Other pollutants come with uncertainty. Finally, the factors influencing urban non-point source pollution are discussed, such as the intensity, duration and quantity of rainfall, the urban land use, the condition of atmospheric pollution, and the cleaning condition of land.