The Efficiency And Influencing Factors Of Ecological Ditch To Remove Nitrogen And Phosphorus Pollution From Agricultural Surface Sources

Over the past few years,the impact of agricultural non-point source pollution on the quality of water has exceeded the impact of point source pollution,posing a serious threat to the quality of water and ecosystem safety.Ditch,as a measure of process control,is an intermediate bridge connecting pollution sources and receiving water bodies,and it is also a key part of agricultural non-point source pollution control management.Therefore,exploring the purification efficiency of ecological trenches and analyzing the key factors affecting nitrogen and phosphorus removal from ecological trenches have important theoretical and realistic significance for the scientific and rational construction of ecological trenches and effective control of agricultural nitrogen and phosphorus pollutants.This paper studies the efficiency and influencing factors of nitrogen and phosphorus removal in ecological ditches through field in situ monitoring and simulation experiments.First,by observing the nitrogen and phosphorus removal efficiency of self-built ecological ditches,the nitrogen and phosphorus removal efficiency of ecological ditches was analyzed;second,by constructing different types of ecological ditches to conduct simulation tests to explore different water blocking methods,different plant combinations and different Under the condition of matrix formation,the purification efficiency of ecological ditches is identified,and the most significant influencing factors for the purification efficiency of ecological ditches are identified.Finally,through research,it is expected to provide theoretical support for the construction and research of ecological ditches.The result is as follows:?1?The Total nitrogen?TN?concentration value of living ditches and farmland ditches exceeds the total nitrogen standard limit of 2.0 mg/for the Environmental quality standards for surface water?GB3838-2002?for agricultural water areas and general landscape requirements?type V?L;Total phosphorus?TP?concentration value does not exceed the standard.?2?From the time scale,the highest values of TN,Total dissolved nitrogen?TDN?,Nitrate nitrogen?NO₃^--N?,Ammonium nitrogen?NH₄⁺-N?,and Nitrous nitrogen?NO₂^--N?concentrations in living ditches are mainly concentrated around February2019.The highest values of TP,Total dissolved phosphorus?TDP?and Phosphate(PO₄^3-)concentration of living ditches are mainly concentrated around February 2019.The highest values of TN,TDN and NO₃^--N concentrations in farmland ditches are mainly concentrated around February 2019.The overall changes of NH₄⁺-N and NO₂^--N are relatively stable.The first highest value of phosphorus concentration in farmland ditches occurred in September 2018,and the second and third highest values occurred around November 2018 and February 2019,respectively.From the perspective of spatial scale,the concentration of TN,TDN,NO₃^--N,NH₄⁺-N,NO₂^--N,TP,TDP and PO₄^3-in the living ditches and farmland ditches showed a decreasing trend from the source to the end along the ditches flow direction.?3?The TP output flux of the living ditch is 10.07 kg/a.The TN output flux is180.28 kg/a.The TP output flux of farmland ditches is 0.68 kg/a.The TN output flux of farmland ditches is 22.14 kg/a.?4?The average purification efficiency of living ditches for TN,TDN,NH₄⁺-N,NO₂^--N and NO₃^--N is 36.54%,36.75%,55.02%,46.68%and 39.38%,respectively.The average purification efficiency for TP,TDP and PO₄^3-were 34.65%,36.54%and64.73%,respectively.The average purification efficiency of farmland ditches for TN,TDN,NH₄⁺-N,NO₂^--N and NO₃^--N is 51.92,52.44%,53.05%,61.08%and 48.22%,respectively.The average purification efficiency for TP,TDP and PO₄^3-were 44.98%,50.43%and 58.78%,respectively.?5?Under different water-blocking methods,the combination of no interception&copper grass has high purification efficiency for nitrogen and phosphorus,and the ecological interception dam and ecological permeable dam also have good purification efficiency.Among different plant combinations,yellow calamus emery plants and foxtail algae submerged herbs are the preferred varieties of plant combinations.In different matrix combinations,soil,pebble and mudstone can be used as the first-choice materials for constructing ecological ditches.