Study On Rainfall Runoff Pollution Process Of Different Underlying Surfaces In University Campuses And Their Periphery

Urban non-point source pollution is an important reason of water pollution in urban rivers.Pollutants accumulated on different underlying surfaces are discharged into the receiving water body by runoff which was generated by rainfall on the ground.Therefore the relationship between rainfall process,surface runoff process and runoff pollution process is an urgent problem to be solved in urban non-point source pollution research.In the study,different underlying surfaces of campus and its surrounding areas were selected as the research objects.Rainfall process,surface runoff process and pollution process were measured.Based on the measured data,the relationship between each process was analyzed,and the pollutant output coefficients of different underlying surfaces and the discharge of runoff pollution in the study area were calculated,which provided a scientific basis for the treatment of urban non-point source pollution.The main research contents include:(1)The correlation analysis of measured rainfall and runoff shows that there is a significant positive correlation between rainfall and runoff of cement pavement and asphalt pavement.The power function relationship between runoff yield time of different underlying surfaces and average rainfall intensity before runoff yield was determined.(2)The analysis of the measured water quality change process shows that the peak concentration of pollutants appears in the initial stage of runoff,and then shows a downward trend.The correlation analysis of runoff process and pollutant concentration change process produced by single rainfall shows that pollutant concentration change is positively correlated with runoff intensity.The correlation between rainfall and pollutant concentration in different rainfall fields was analyzed.The results showed that there was a negative correlation between rainfall and pollutant concentration.(3)Statistical analysis of water quality sampling data of different underlying surfaces shows that the average values of suspended solids,ammonia nitrogen and COD of main pollutants in campus and its surrounding areas are 291.60 mg/L,2.14 mg/L and 50.22 mg/L,respectively.COD and chloride are the main pollutants in the asphalt pavement of Nongda West Lane.The main pollutants on the roof are ammonia nitrogen and nitrate nitrogen.(4)The pollutant discharge amount from different underlying surfaces was calculated.The results show that the pollutant output coefficients of old residential areas and catering streets are on the high side as a whole,which is the key control area of urban runoff pollution.Based on the annual average precipitation,the general situation of the study area and the measured data of runoff pollution,the annual average pollutant discharge amount of suspended solids,ammonia nitrogen and COD in the campus and the surrounding study area were calculated to be 142.31 t,0.95 t and 22.06 t,respectively.Taking suspended solids as an index,the relationship between suspended solids concentration and rainfall in runoff was analyzed.The results show that closure treatment of initial rainfall runoff can effectively reduce runoff pollution emissions.