The Pollution Characteristics,Sources Identification And Ecological Risk Assessment Of PAHs In Urban Runoff

With the accelerated urbanization and urban sprawling, degradation in urban environmental quality has becoming a concern for both academic and administrative sectors. In particular, water pollution in urban environment has gained more and more attention. Considering the characteristics of the urban impervious surfaces, urban storm runoff pollution has become a major cause of degradation in quality of urban water bodies. Pollutant loading from strom runoff has been regarded as an important component of the non-point source pollution in urban areas. Understanding of the characteristics of urban runoff pollution, especially the transfer and loading of PAHs in urban environment is quite crucial for improving urban aquatic environmental.This paper is supported by the projects of "Major Science and Technology Program for Water Pollution Control and Treatment" (Grant No. 2009ZX07317-006), National Natural Science Foundation (Grant No.40971259) and the project of Excellent Academic Leaders of Shanghai (Grant No. 10XD1401600). Wenzhou and Shanghai that we discussed different types of urban surfaces are the cities we pay attention to. The contents trends of PAHs in urban runoff, first flush effects and environmental effecs are the main points we concerned. In the view of system of urban runoff, river band soils, river water and sediment, we put research in the sources identification and ecological risk assessment of PAHs.The PAHs EMC of different imperious surfaces in urban runoff show the flush effects. With the minor rainfall intensity, EMC values are higher which may be the reason that dilution effect is more significant in the condition of larger rainfall intensity. The PAHs EMC values of confluence discharged into river water directly are generally high. The values of two districts are 0.65mg·L-1 and 0.43 mg·L-1, which show the large influence to the receiving water.The PAHs contents trends of different surfaces in urban runoff show that flush effects are represented of PAHs contents trends in tiny rain intensity, meanwhile dilution effects are showed in bigger urban catchment of huge rain intensity which may be the reason that huge quatity of runoff which diluted the pollutant.The variation of PAHs contents is smaller in the conditon of smaller rainfall intensity for the different underlying surfaces of the same rainfall event. Meanwhile, large variation is show in the larger rainfall intensity. First flush effects of PAHs are more easier happened in bigger urban catchment. What's more, the larger rain intensity shows better flush ability.In the system of urban runoff, river band soils, river water and sediment, the environmental influences show the differences of underlying surfaces of rainfall events. Under the condition of minor rainfall intensity, the EMC values of Jiushan traffic road and Shanxia residential roof are highest which means the heavy pollution to the receiving water. Meanwhile, minor pollution is shown under the condition of greater rainfall intensity. That may be the reason of dilution of great runoff volume. The PAHs EMC of river band soils and sediments which shows the long-term effect of human activities and environmental influence is minor than that of runoff and river water which the environmental influences of medium and low rings of PAHs are more serious.The sources identification of PAHs shows the similarity of different media for the system of urban runoff, river band soils, river water and sediment. Fla/(Fla+Pyr) mostly shows the souce of grass, wood and coal combustion; Ant/(Ant+Phe) shows combustion souce; BaA/(BaA+Chr) of most dust and soils shows the mix souce, and others show the combustion souce; IcdP/(IcdP+BghiP) shows the multiple souces of petroleum leakage and combution. Ecological risk assessment of traffic roads is the most serious in different kinds of urban surfaces. The PAHs ecological risk assessment of river water which shows the recent effect of human activities and environmental influence is more serious than that of river band soils and sediments.