Research On Analysis And Reduction Of Rainfall-runoff In Square Based On LID Technology

Nowadays,the original green spaces,lakes and farmland are gradually replaced by buildings,impervious floors and squares as the constant expanding city scale.Meanwhile,human activities have also changed the structure as well as function of urban environment.The earth-shaking changes in the pattern of urban land use also resulted in many serious hydrological problems,such as poor rainwater infiltration,severe pollution of rainfall runoff and frequent water-logging hazards.As a part of the public environment,square environment is a typical representative for researching the rainfall runoff in the public environment because of its large proportion of impervious pavement,poor rainwater penetration performance and less rainfall infiltration underflow.Based on the research object of Zhongjun Plaza in Hongqiao Business District,Minhang District,Shanghai,this thesis analyzes the air pollution and rainfall in the study area over the past years.According to the collection and detection of the three rainfall runoffs in the study area,along with the pollutants reduction experiments on several common substrates,it is concluded that as follows:?1?The measurement of EMC_S values of various pollutants within the study area finds that the EMC_S values of the three runoff water quality pollutants within the study area exceeded the Standard IV of Surface Water Environmental Quality GB3838-2002.Among them,the EMC_S values of COD in all areas exceeded Standard V,which indicates a relatively serious pollution in Zhongjun Plaza in Minhang District.The areas having higher EMC_S values of SS,COD,TN,and NH₃-N include Area C2?underground garage entrance?,Area B?main entrance of commercial square?,and C1?secondary entrance/underground garage entrance?.?2?It is concluded from the detection of concentrations of COD,TN,NH₃-N and SS in rainfall runoff during different time periods:The runoff pollutant concentration in different rainfall periods is negatively correlated with time.The concentration of different pollutants in10min period was 2-120 times higher than that in the 120min period.This indicates that most of the pollutants in the rainfall runoff come from road surface pollution,whose concentration decreases as time extension and rain wash.?3?During rainwater runoff,the mass of SS is proportional to the concentrations of COD,TN and NH₃-N.Experiments show that runoff pollutants exist in the suspension in the form of particulate adsorption.The content of pollutants,such as SS,COD,TN and NH₃-N,can be effectively controlled by cleaning the road or initially precipitating and filtering the rainfall runoff in early stage.?4?Different substrate types and storm intensities significantly influence the removal of pollutants.In the rainfall reappearing period of 2a,vermiculite,among sand-based permeable brick,perlite,ceramsite and graded gravel,plays the best effect in removing the pollutants of C₆H₁₂O₆,NH4Cl and KH₂PO₄;In the rainfall reappearing period of 5a,permeable brick,vermiculite and perlite all play better effect in removing pollutants.All of above substances play better effect on removing NH4Cl with the removal rate between 45%and 60%.?5?The permeation experiment of percolation column shows that the instantaneous permeation rate of ceramsite is the highest.In the rainfall reappearing periods of 2a and 5a,the time from simulated rainwater runoff to permeable water respectively is 477.40s and680.47a,which is 72%-80%faster than that of perlite,and 82%-85%faster than that of meteorite.?6?In the environmental design of Zhongjun Plaza in Minhang District,the plants with better rainwater runoff reduction and purification effect are selected based on plants'drought resistance,anti-waterlogging capacity,appearance,and purification ability.It is a comprehensive design that aims to optimize business environment,enhance office quality and improve the development based on low influence LID technology.By means of applying the principles of ecological design and maximizing rainwater utilization into landscape environment design,it will become more in line with the construction of Shanghai's“Green Ecology Demonstration Zone”and“first low carbon business circle”.