| Water environment is an important part of the urban ecological environment, water environment pollution generally can be divided into point sources and non-point source pollution, due to the point source pollution is remarkable and intensity, so related research carried out early and investment management cost high. After the control of point source pollution, the non-point source pollution is gradually emerging, and the rainfall runoff is the main driving force for the transformation of pollutant transport, and is the hot and key point of the research on urban non-point source pollution.Urbanization is the inevitable trend of social and economic development in china. When heavy rain occurs, the underlying surface of a large amount of pollutants is washed and the runoff is produced, which causes pollution to the urban ecological environment. Roof is one of the 3 main underlying surfaces?pavement, roof, and grassland? in the city. In order to further understand the general characteristics of urban rainfall runoff pollution, this paper based on outdoor localization observation and indoor simulation experiment, comparison of different functional areas of the mixed atmospheric deposition and different simulate roof of runoff pollution process.?1? Take an example of Beijing city of different typical functional areas of natural mixed deposition samples for contaminant analysis. The analysis shows that Beijing city natural mixed atmospheric deposition seriously overweight, belonging to the inferior V class water. TN is the major pollutant of mixed urban atmospheric deposition; and nitrogen is the main nitrate of the mixed urban atmospheric deposition in the urban city, while ammonium nitrogen is the main nitrate of the foreat on the edge of city. According to the water quality of the pros and cons collation, Mangshan > Botanical Garden> Ecology Center, indicating that mixed atmospheric deposition have obvious spatial differences, and positively correlated with the extent of human activity?2? Research on the characteristics of rainfall runoff pollution of the residents of different materials?cement, linoleum, simulated roof tiles, tiles, iron?, shows that the material of the roof has a significant influence on the runoff water quality. Due to the roofing material is rough and generally adopted "cascading" laying, roofing felts rainfall diameter water quality is the worst, and TSS trend compared to the rest of the roof has a certain lag;The average rainfall runoff pollution of the roof is compared with the results of previous studies in the same area, the results show that the control and control of air pollution in Beijing city has achieved initial success, and it can promote the reduction of pollutants in rainfall runoff;?3?The Beijing malthoid roofing intervals for the rainfall runoff process monitoring 5min, the routine detection index is combined with the method of nitrate nitrogen and oxygen stable isotope. The characteristics of the duration of rainfall pollution in Beijing, the initial erosion phenomenon, pollutant sources and so on are analyzed further. Because of the different particle size of the particles affected by rainfall, the ability of migration is different, TSS is a zigzag distribution.?4?Routine detection index in the quality of the nitrate nitrogen concentration in the process of rainfall runoff changes had no obvious regularity, but the experimental analysis of nitrate nitrogen and oxygen stable isotopes, ?15N-NO3- and ?18O-NO3- at the beginning of the rainfall runoff began to change significantly, while after the long rain wash, ?15N-NO3- and delta ?18O-NO3- values are stable in a smaller range, ?15N-NO3- and the change of ?18O-NO3- are in line with the multivariate linear regression equation, proves that the nitrate nitrogen and oxygen stable isotopic characterization of nitrate pollution has more obvious; After analysing the nitrate pollution source of rainfall runoff process by using nitrate nitrogen oxygen stable isotope methods, it can be concluded that the nitrate nitrogen has diffferent sources in different period of rainfall runoff.; In the early period nitrate nitrogen isotopes are mainly from asphalt roofing rainfall runoff whose values range from 0.425 to 24.94 ‰, while in the midphase the source becomes soil organic nitrogen with the values of ?18O-NO3- ranging from 3.468 to 13.401 ‰. In the late period of rainfall runoff, the nitrate nitrogen mainly comes from the chemical fertilizer and NH4+ in the rainfall. |
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