Research On Allocation Of Buffer Strips In Urban Riverside Based On Effective Removal Of Pollutants

In recent years,urban water environmental problems have become severe.Non-point source pollution is the main cause of urban water environment problems.Non-point source pollution is difficult to control because of its characteristics of scattered sources,complex formation,and difficulty in monitoring.Research at home and abroad shows that riparian buffer strip is one of the best management measures for controlling non-point source pollution.Therefore,the research on the construction of vegetation buffer zone is significance for ensuring urban water environment quality.In addition,the characteristics of riparian buffer strip make it available for the construction of sponge city.In this paper,the author studied the pollutants concentration of rain water,small test of buffer strip,and field test of buffer strip.This tests aimed to provide a basis for the construction of buffer strip to purify non-point source pollutants.The result is as follows:I collected the rain water samples from May to July,and measured the concentration of pollutants.I took them as the inlet concentration.The concentration of ammonia nitrogen and COD is large,the pollution is serious,the concentration of heavy metals and nitrites is low,and the pollution is lighter.In order to explicate purification effect and accumulation capacity for copper,lead and cadmium by different herbaceous plants of riparian buffer strips.In the small test,three species of herbaceous plants(Lolium perenne,Poapretensis and Medicago sativa)were selected as experimental materials.Self-designed lab-scale equipment simulated buffer strips.The purifying effects of different single ways of planting were studied through simulating runoff with artificial water.The results showed that Medicago sativa buffer strips had highest removal capacity of copper,lead and cadmium in runoff and seepage flow.The runoff average removal rate of copper,lead and cadmium reached 82.79%,68.73%and 92.02%,and the seepage average removal rate of copper,lead and cadmium reached 89.15%,74.27%and 94.73%.The heavy metal total accumulation of three plants follows the order:copper>lead>cadmium.Copper and lead contents that in Medicago sativa was significantly higher than Lolium perenne and Poapretensis.Copper and lead total accumulation was 13.45 mg and 1.01 mg in Medicago sativa.The accumulated content of cadmium was about 0.50 mg in Medicago sativa and Poapretensis,The results showed that Medicago sativa buffer strips had best purification effect for copper,lead and cadmium.In the field test,I selected Lolium perenne,Poapretensis,Medicago sativa and Syringa oblata Lindl.were used to construct the buffer strip.Seven test plots were established with single planting and mixed planting.The results showed that the buffer strip of mixed plantation had better purification effect on ammonia nitrogen and orthophosphate in runoff and seepage than the single vegetation buffer strip.The Syringa oblata Lindl.and Medicago sativa mixed buffer strip had the highest removal rate for ammonium nitrogen and orthophosphate in runoff and seepage.The single Medicagosativa buffer strip had the best purification effect on heavy metals,and the average removal rate was higher than that of the mixed plant plots.