Nutrient Attenuation In Agricultural Surface Runoff By Grass Buffer Strips

At present,the situation of agricultural non-point source pollution in China is very serious.The control and treatment of farmland non-point source pollution is an important task for a long period of time to come.China’s current point source pollution control has achieved initial success,but due to the amount of non-point source pollution The characteristics of wide coverage,rapid changes,etc.determine the difficulty of its governance.Foreign research and practice show that the use of plant systems to construct turf buffers is an effective means of intercepting farmland non-point source pollutants and improving river and lake water quality.Therefore,by optimizing the arrangement of grass species and constructing a suitable farmland turf buffer zone,it has the best ecological benefits to control nitrogen and phosphorus pollutants and intercept sediment,and it has become the most urgent task for ecological environment construction and protection in the Southern Red Soil Region.This study selected six species of common grass plants in the southern red soil region: Trifolium repens,Trifolium repens L,Trifolium repens,Festuca elata Keng ex E.Alexeev,Cynodon dactylon(L.)Pers.,Paspalum notatum Flugge,Imperata cylindrica(L.)Beauv.The turf buffer zone was constructed by means of unicast and mixed broadcasting,and an outdoor simulated runoff flushing experiment was carried out.The combination of outdoor testing and indoor measurement analysis was used to study the buffer zone’s ability to control and control terrestrial pollutants.The concentration of water pollutants,slope and buffer zone width were used to explore the effect of turf buffer zone on the pollution of farmland non-point source pollution.The main conclusions are as follows:(1)In the unicast test,the average removal rate of SS and TN in the runoff water was the highest,reaching 61.88% and 31.11% respectively.The white trifoliate buffer zone had a higher removal rate of TP in runoff water with an average removal rate of 25.6%.(2)Under the condition that the concentration of influent pollutants is constant,the sorting effect of the mixed-flow buffers on runoff SS is: A2>A1>B2>B1>A3>B3>C,The purifying effects of TN and TP in runoff and seepage waters are as follows: A2>A1>A3>B2>B1>B3>C,Among them,A2 turf buffers have the best removal effects on runoff SS,runoff TN,seepage TN,runoff TP and seepage TP.The removal rates are 66.33%,30.74%,45.26%,27.06% and 54.95%,respectively.(3)Comparing the removal efficiency of TN and TP in the buffer zone,it can be clearly seen that the removal effect of the mixed sod turf buffer on runoff TN is slightly stronger than that of runoff TP,and the removal effect of seepage TN is weaker than that of seepage TP.From the fitting relationship between biomass and runoff seepage pollutants,it can be seen that with the increase of above-ground biomass,runoff and seepage of the buffer zone constructed by each turf have basically increased the removal rate of pollutants.The greater the underground biomass,the better the purification effect on seepage TN and TP.(4)The removal rates of pollutants in runoff TN and TP showed a significant decreasing trend with the increase of slope,while the reduction rates of seepage TN and TP pollutants did not change significantly when the gradients were 3°,5°,and 7°.The effect of slope on pollutants of runoff TN and TP is greater than that of pollutants of seepage TN and TP.The mean removal rate of turf shed SS was significantly higher(p<0.05)than that of C(no plant blank group),and the interception effect was enhanced along the course;the average removal rate of TN and TP was significantly(P<0.05)higher than that of runoff.TN,TP.(5)In the flooding stress experiment,the retention of TN and TP mainly occurred in the first 3days.On the 1st day,the TN and TP contents had the greatest impact.Afterwards,the nitrogen and phosphorus contents in the overlying water changed slowly and stabilized.Regardless of whether TN or TP,plants are through the break the interface balance,promote its exchange at the interface,thereby accelerating the pollutants into the soil speed,other conditions are the same,you can retain more TN,TP,enhance the buffer zone intercept surface source The capacity of pollutants.