Study On The Engineering Technology Of Agricultural Non-point Source Pollution Reduction In Plateau Lake Ecological Buffer Zone

In recent years,the treatment of agricultural non-point source pollution in plateau lakes has always been the top priority of ecological environment protection in Yunnan Province.Agricultural non-point source pollution is an important pollution source of water pollution problems such as lakes and reservoirs,and it is also the primary problem of water environment pollution.Agricultural non-point source pollution control has become the focus and difficulty of Yunnan plateau lake pollution,and ecological buffer zone is one of the important measures for the protection and treatment of plateau lakes.Although Yunnan has achieved phased success in the prevention and control of agricultural non-point source pollution in plateau lakes,the water quality of plateau lakes has improved slowly,and agricultural non-point source pollution is still severe.Due to the influence of surrounding industrial and agricultural production,urban construction and residents’daily life,the aquatic and waterfront habitats in the Dianchi Lake Basin have been damaged to varying degrees.The problems of water quality deterioration and ecosystem degradation are becoming more and more serious.The function of the original ecological buffer zone is declining or even disappearing.Therefore,it is of great significance to study the key technologies of agricultural non-point source pollution reduction project in plateau lake ecological buffer zone.This paper describes the relationship between ecological buffer zone and hydrology,topography,soil,vegetation and other factors.Aiming at the characteristics of various pollution types,complex pollution sources and high pollution intensity in the lakeside buffer zone of plateau lakes,the existing point,line and non-point source control technologies were analyzed and integrated by investigating the original agricultural non-point source pollution in Kunming Dianchi Dawan Modern Ecological Agriculture Demonstration Park.The topography,hydrology,soil,vegetation and other factors of the ecological buffer zone in the study area were investigated by referring to the multi-technology linkage synergistic interception and pollution control system such as runoff non-point source interception and storage,in-situ bypass treatment of rivers,ditches and canals into the lake,and pollution control at the end of wetlands into the lake.Through the water sample collection of the paddy wetland system in the ecological buffer zone of Kunming Dianchi Lake in2022,the pollution reduction assessment of the ecological buffer zone of Kunming Dianchi Lake was carried out.The results are as follows:（1）The original flowers and vegetables in the study area were planted in low-end greenhouses,and a large amount of chemical fertilizers and chemical pesticides were used.Under the accumulation of many years,the soil eutrophication was serious,the biodiversity and ecological balance were destroyed,and the management mode of’big water,big fertilizer and big medicine’was adopted.In addition,the traditional agricultural irrigation,the water system is not connected,the water use efficiency is low,and the water resources are wasted seriously.The study area has adopted point,line and non-point source control technologies for agricultural non-point source pollution,such as ditch transformation,establishment of ecological buffer zone paddy wetland system,and formation of multi-level governance system.（2）The altitude of the ecological buffer zone in the study area is 1886 m,and the slope of most sites is less than 30%.The main slope directions are southwest and west;the irrigation water in the study area is mainly based on the upstream Liangwang River water,Dawan Longtan natural water source and natural rainfall water storage.The soil in the study area is red soil acid soil and paddy soil;the vegetation in the study area is mainly artificial vegetation,and it is mainly concentrated in the ecological science popularization area of Dianchi Lake.Artificial vegetation types include arbor forest,green belt,shrub forest,nursery,artificial grassland and cultivated land.A total of 153 plant species are distributed,mainly distributed in the ecological science popularization area of Dianchi Lake.Among these plant species,there are 34 species of trees,25 species of shrubs,81 species of herbs,10 species of vines,and 2 species of epiphytes.（3）The average concentration of total phosphorus at the inlet of the paddy wetland system in the ecological buffer zone of the study area was 0.394mg·L^-1,and the average concentration at the outlet was 0.069mg·L^-1.The average reduction rate of total phosphorus was 78.4%±12%.Among them,the reduction rate was the highest in May,up to 91.12%,followed by August,up to 88.6%,while the reduction rate in January was the lowest,only 68.24%.The average concentration of ammonia nitrogen at the inlet of the paddy wetland system was 0.591mg·L^-1,and the average concentration at the outlet was 0.199mg·L^-1.The average reduction rate was 70.47%±11%.The highest reduction rate was 88.13%in September,followed by 84.37%in August,and the lowest reduction rate was 49.36%in March.The average concentration of total nitrogen in the inlet of the paddy wetland system was5.801mg·L^-1,and the average concentration in the outlet was 1.235mg·L^-1.The average reduction rate was 75.7%±11%.Among them,the reduction rate was the highest in August,up to 88.6%,followed by May,up to 86.74%,while the reduction rate in January was the lowest,only 66.43%.In summary,there are relatively few species naturally distributed in the ecological buffer zone of the study area.This is related to the long-term human influence,transformation and utilization.The expansion and optimization of the vegetation planting area should be completed as soon as possible to improve the ecological benefits of the ecological buffer zone and maintain the ecological balance.The removal effect of agricultural non-point source pollutants in the paddy wetland system of the ecological buffer zone in the study area was better in summer and autumn,but the effect was poor in winter and spring.The study area has adopted point,line and non-point source control technologies for agricultural non-point source pollution,such as ditch transformation,establishment of ecological buffer zone paddy wetland system,formation of multi-level control system,and achieved good results.This provides useful experience and reference for other plateau lake areas to solve the problem of agricultural non-point source pollution.