| The phenomenon that urban runoff scours ground surface and carries pollutants into the water body has caused a series of environmental problems. Lake District, Wuxi city was chosen as research area in order to study the characteristics of non-pointed pollution caused by urban runoff in typical rapid urbanization area. Runoff monitoring was done to estimate the degree of pollution and measures were also taken to control the pollution and solve the problem brought by runoff in this area. Integrated control technology was finally built on the basis of area research. The main conclusions of the study are as follows:(1) Rainfall was abundant with low inter annual variability in the Wuxi city. The nutrient pollutants concentration of local urban runoff was high while heavy metal concentration was relatively low.(2) The degree of contamination of urban runoff was affected by dryness period, peak rainfall intensity, peak flow rate, cumulative rainfall, peak rainfall, season and underlying surface condition. During rainfall process, the pollutants concentration of runoff was often higher at the beginning and relatively lower at the end of rainfall. The phenomenon of first flush effect was observed during runoff characteristic study in Wuxi.(3) TSS, COD and TP were all well removed in the infiltration systems with different combinations. Growing plants in the composite infiltration system had few impact on the removal efficiency in the study period. Systems with artificial fillers showed a better removal efficiency than these with native soil.(4) The addition of wood chips can significantly improve the removal rate for TN and NO3--N. However it lowered removal efficiency for COD, TP and NH3-N of the urban runoff. Compared with filling layered wood chips in the composite infiltration systems, mixing them with other adsorption packing can help to reduce pollutant leaching and reach a higher removal efficiency for TN.(5) Adsorption swale had high removal efficiency for runoff pollution. The average removal rate of adsorption swale for TSS, COD, TP, DTP, TN, NH3-N, NO3--N was 89.9%, 58.5%, 80.9%, 51.0%, 54.8%, 77.6%, 46.5% and 74.0%, respectively. It showed that the adsorption swale could effectively reduce the amount of pollutant carried by road runoff from discharging into water bodies.(6) The discrete adsorption barrier for undercurrent treatment had a good effect on reducing runoff pollution. Changing the ratio of wood chips and adsorption packing had low impact on the system. The removal rate of the two system with different ratioof wood chips for TSS, COD, TP, TN, NH3-N, NO3--N and NO2--N was 92%, 70%, 90.9%, 70.3%, 57.7%, 93.1%, 91.6% and 90%, 70%, 91.2%, 71.8%, 58.8%, 92.9%, 90.7%, respectively.(7) The average removal rate in the long term of situ runoff purification parking lot for TSS, COD, TP, DTP, TN, NH3-N, NO3--N and NO2--N in the runoff was 89.3%, 66.4%, 83.3%, 55.3%, 43.6%, 86.8%, 28.5% and 75.8%, respectively. The situ runoff purification parking lot can effectively reduce the amount of runoff pollution from discharging into the water body. The pollutants concentration of reuse water in the water tank of the situ runoff purification parking lot maintained stable at a low level during the year. |
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