| With the rapid development of China’s economy and the continuous acceleration of urbanization,the changes in urban landscape patterns have made urban rainfall-runoff pollution the second largest pollution source after agricultural non-point source pollution.The urban rainfall-runoff pollution caused by rainfall erosion has posed a serious threat to the surface water environment in China.Controlling urban rainfall-runoff pollution is particularly important for improving the quality of urban water environment.This study selected rainfall runoff from different functional areas in Beijing as the research object.By using on-site sampling and laboratory water sample measurement methods,the variation patterns of rainfall-runoff pollutants,correlations between pollutants,and correlations between EMC and rainfall characteristics were fully analyzed.The DOM components and sources of rainfall-runoff were explored through three-dimensional fluorescence spectroscopy technology combined with parallel factor analysis,Finally,the Analytic Hierarchy Process（AHP）and Fuzzy Comprehensive Evaluation（FCE）were introduced to evaluate the water environment risk of rainfall runoff.Intended to provide theoretical basis and technical support for the management of rainfall-runoff pollution in Beijing and other northern cities.The main research conclusions are as follows:（1）The formation time of pollutant concentration peaks in different functional areas and different rainfall events is different,but the peaks remain within 10-30minutes,and generally show a trend of first increasing,then decreasing,and finally gradually stabilizing with the change of rainfall duration.The most heavily polluted functional areas are transportation areas,followed by residential areas,and the least polluted cultural and educational areas.（2）The order of EMC in rainfall-runoff pollutants in the three main functional areas from large to small is transportation area>residential area>cultural and educational area.The average EMC values of various pollution indicators SS,COD,TP,TN,and NH3-N in the traffic area are 1432.19 mg/L,218.19 mg/L,0.78 mg/L,2.82mg/L,and 1.84 mg/L,respectively;The average EMC values of various pollution indicators in residential areas are 671.59 mg/L,101.95 mg/L,0.71 mg/L,2.53 mg/L,and 1.76 mg/L,respectively;The average EMC values of various pollution indicators in the cultural and educational district are 590.01 mg/L,88.74 mg/L,0.70 mg/L,2.50mg/L,and 1.61 mg/L.The EMC value of SS pollutants in the three main functional areas has exceeded the third level standard;The EMC values of COD and TN pollutants in the three main functional areas have exceeded the Class V water standard;The EMC values of TP and NH3-N pollutants in the three main functional areas have exceeded the Class V water standard.There is a correlation between rainfall runoff pollutants in the three main functional areas,and there is a good correlation between SS and other four pollutants such as COD,TP,TN,and NH3-N in residential areas.The average correlation coefficient R2 is 0.964,0.915,0.898,and 0.864,respectively;The correlation between SS and other three pollutants such as TP,TN,and NH3-N in cultural and educational areas is good,and the average correlation coefficient R2 is 0.941,0.870,and 0.838,respectively;The correlation between SS and other four pollutants such as COD,TP,TN,and NH3-N in the traffic area is good,and the average value of the correlation coefficient R2 is 0.865,0.849,0.912,and 0.868,respectively.There is a certain correlation between EMC and rainfall characteristics in three main functional areas.The main influencing factors of rainfall-runoff pollutants in residential areas are rainfall,average rainfall intensity,and maximum rainfall intensity;The main influencing factors of rainfall-runoff pollutants in cultural and educational areas are rainfall,average rainfall intensity,and maximum rainfall intensity;The main influencing factors of rainfall-runoff pollutants in traffic areas are rainfall,average rainfall intensity,and maximum rainfall intensity.（3）The DOC concentration of rainfall-runoff presents light rain>moderate rain>heavy rainstorm>rainstorm.The humification degree of rainfall runoff in traffic area is the largest,followed by residential area,and cultural and educational area is the smallest;The parallel factor analysis method showed that the DOM components of the four rain patterns had five fluorescent components,namely,three humic acids,one fulvic acid,and one protein;The total fluorescence intensity of the rainfall-runoff DOM presented a descending order from large to small,followed by traffic areas,residential areas,and cultural and educational areas;The fluorescence parameter analysis showed that the BIX value was mainly between 0.4 and 1.0,the HIX value was less than 4,and the FI value was greater than 1.9.The DOM in rainfall runoff was mainly generated by the combination of endogenous and exogenous inputs,and the degree of humification was relatively low.Rainfall patterns had no significant impact on the degree of humification and source of DOM.（4）The three main functional areas,including residential areas,cultural and educational areas,and transportation areas,are at risk level V,which is a high risk level.The causes of serious water environment pollution may be fertilization of surrounding herbs,exhaust gas from vehicles,friction between the ground and tires,discharge of domestic and traffic sewage,road garbage,lack of ground cleaning,and other factors.Effective measures need to be taken for risk management based on the pollution situation in different functional areas. |
