Study On The Reduction Characteristic Of Non-point Pollution In Erhai Lake Basin Through Terrestrial Vegetation Buffer Strip Technology

Water pollution caused by non-point source pollution has become an important environmental issue in our country. Non-point source pollution is extremely hard in governance because of its dispersed source, hard to form and difficult to monitor. Research at home and abroad show that vegetation buffer strip is an effective measure to control non-point source pollution and improve water quality. Therefore, the research of vegetation buffer strip construction technology is of great importance to protect the water environmental quality. In this paper, the author studied the terrestrial plants status of Erhai lake buffer zone, small test of buffer strip and field test of buffer strip. With this test, the author determined engineering parameters of terrestrial vegetation buffer strips and proposed a terrestrial vegetation buffer strip construction mode. The results listed as following:The results showed that terrestrial plants of Erhai Lake buffer zone were abundant. There were 8 kinds of arbors,58 kinds of herbs. Yunnan Willow was a dominant species, reached 80.94% of arbors. Recommend arbor configuration of Erhai Lake buffer zone were as followed: the zone near lake planted with Yunnan Willow, the intermediate zone planted with Pond Cypress, the zone near road planted with Metasequoia.In the lab-scale test, the inlet concentration of TN, TP and Permanganate Index were 10.00 ±1.12 mg/L、1.00 ± 0.13 mg/L and 30.00 ± 2.35 mg/L respectively. Sward test strips’reduction effect is much better than blank test strip. Based on the overall reduction effect of each pollutant, mixed grass, Pnnisetum, Cynodon dactylon performed well and grew better.In the study of buffer zone’ construction parameters,20 meter wide sward buffer strip could remove 30% of the pollutant (SS、TN、TP and Permanganate Index) in the run-off and 55% of the pollutant (TN、TP and Permanganate Index) in the seepage. Mixed grass had the good growth condition, large biomass and best reduction effect. The reduction effect of non-point pollution increased along width of sward buffer strips, and the front section of these strips showed stronger reduction than the rear one. The corresponding order in the reduction effect of run-off pollutants was as followed:2% slope> 4% slope>6% slope. The lower slope, the better reduction effect of buffer strips.Half a year’s field test monitoring results indicated that mixed grass buffer strip had a good reduction effect of the pollutant in the run-off in both warm season and low temperature season, while Cynodon dactylon and Zoysia japonica had lower reduction effect in low temperature season than warm season.Terrestrial vegetation buffer zone mode proposed was divided into three districts, whose width was over 100 m and was of 1:3:1 configuration. First district was planted with native arbors, Second district was planted with man-made trees and shrub, Third district was planted with herbs.This buffer zone construction mode had the function of water purfiction, soil and water conservation, habitat and aesthetic value.