Study On Removal Efficiency Of Agricultural Runoff Pollutants By Riparian Buffer Strips Of Different Slopes

Water pollution control is an important task in environmental protection of China.Nowadays,point sources pollution control have brought noticeable achievements,but its large-volume,rapid changes and other characteristics make non-point sources pollution hard to deal with. Researches and practices abroad indicate that riparian buffer strips is an effective way to control agricultural non-point sources pollution and improve water quality.Based on "Study on Practical Technology of Suzhou Creek Comprehensive Rehabilitation Project Stageâ…¢"(NO.: 04DZ12032),the test on "Riparian Buffer Strips-Agricultural Non-Point Sources Pollution Control Technology in Upper Stream of Suzhou Creek" was carried out and the removal efficiency of agricultural runoff pollutant by riparian buffer strips of different slopes was importantly analyzed.First,five common greenswards(Cynodon dactylon,Festuca Arundinacea,Trifolium repens,Lolium perenne and Dichondra repens) in Shanghai were chosen to design grass vegetation selection test.The main conclusions were as follows:In the same condition,the biomass of Cynodon dactylon and Trifolium repens were the biggest.The runoff SS removal efficiency were alse the highest,were 84%and 81%.For the 5 buffer strips,runoff TN and TP removal efficiency were relatively weaker. But for seepage TN and TP removal efficiency,Cynodon dactylon and Trifolium repens were all morer than 80%.In all,Cynodon dactylon were better than Festuca Arundinacea.Because of its obvious superiority in early stage test,Cynodon dactylon was chosen in on-site test.Study on removal efficiency of agricultural runoff pollutant by riparian buffer strips of different slopes was conducted.The main conclusions were as follows:(1) For the 4 test strips of different slopes,the order of removal efficiency of runoff SS and seepage TN,TP were 2%> 3%> 4%> 5%,the end of runoff SS removal efficiency were 84%,80%,77%,72%,the end of seepage TN removal efficiency were 80%,75%,69%67%,and the end of seepage TP were 84%,81%,79%,74%.(2) When the end runoff SS removal efficiency of buffer strips of different slopes reached 80%,the optimal width of 2%slope buffer strip was 16.1m,3%was 18.0m,4%was 20.3m,5%was 24.7m;When the end seepage TN removal efficiency of buffer strips of different slopes reachedâ…£water quality standards,the optimal width of 2%slope buffer strip was 23.4m,3%was 25.2m,4%was 28.8m m,5%was 30.3m.(3) The runoff water and seepage water have some correlation with slopes,and the order of runoff water was:5%> 4%> 3%> 2%;the order of seepage water was:2%> 3%> 4%> 5%.In the condition that the total water was fixed,the bigger the slpoe was,the higher the runoff flow speed was.So the seepage water was small and runoff water was relatively big.On the contrary,the seepage water was big and runoff water was relatively small.(4) The order of runoff and seepage TN,TP removal efficiency were:2%> 3%> 4%> 5%.That is to say,for removal efficiency of TN and TP,2%buffer strip was better than the other 3 strips.