Low-impact Development (LID) Community Non-point Source Pollution Process And Control Effects

With the development of urbanization,impervious surface area and human activities increased,the problem of urban surface runoff pollution become increasingly serious.To solve the problems of urban non-point source pollution and to use the rainwater resources effectively,the state vigorously promote the construction of sponge cities by building low impact development(LID)rainwater system.In this study,the rainfall and runoff processes of the LID community and undeveloped old community in the construction of the sponge city in Zhenjiang were analyzed,and the pre-accumulation of the pollutants and the changes in the rainfall process were investigated.The polluting process and the runoff control effect were assessed preliminarily and the results are as follows:(1)The accumulation of surface sediments in the LID community is 48.9% ± 11.2% less than that of the old community.The pollution load of heavy metals,TN and TP in LID plot sediments was 66.8% ± 9.3%,25.1% ± 32.2% and 52.0% ± 11.2%,respectively.Compared with the old ones,and the proportion of fine particles was 28.2% ± 4.6%.These features help to reduce potential urban non-point pollution.(2)LID community runoff contaminant concentration is lower than that of the old.The runoff concentration in the early stage of rainfall is generally higher than that of the surface water grade ?,and it gradually decreased in the later stage.The concentration of runoff pollutants is related to the characteristics of rainfall,and the initial concentration of runoff pollutants is related to the number of sunny days.The runoff particles are mainly ones with particle size <106?m.(3)Compared to the old community,the LID community can control 77.1%,74.5% and 72.1% of the road,square and parking lot,55.25% and 57.38% of the heavy metal pollution load,the 60.5%,68.0% TN load and 83.4%,60.2% TP load of the road and parking lot,.(4)Through SWMM model simulation,theoretical calculation and practical observation,it is possible to meet the target of 75% of total annual runoff control rate and 60% of non-point source pollution control rate.