The Purification Efficiency And Influencing Factors In Different Ecological Remediation Wetlands Within Lakes Of Central Yunnan

Ecological remediation wetland has the advantage of low operating costs,efficient purification and exclusive landscape benefit.It is widely built for water quality improvement of large-scale water bodies,such as lakes,rivers and reservoirs.There have been a large amount of ecological remediation wetlands built in the plateau lake pollution remediation and prevention processes in Yunnan province.However,due to the limitation on geographic factors and the lack of technical specifications,these ecological remediation wetlands has completely different structures(including the composition of plants vegetation,biomass,biological diversity and hydrological characteristics)and functions.It is as well to form universal technical specifications to promote the pollution remediation and protection across the province.Therefore,in order to normalize the construction,operation and management of ecological remediation wetlands,it is crucial to evaluate the different types of wetlands and their efficiencies,and explore the key ecological factors that determine the purification efficiency.In the current study,five different ecological remediation wetlands built around Dianchi Lake and Puzhehei Lake(East River Wetland,Laoyuhe Wetland,Baiyuhe Wetland,Laojiugou Wetland,and Nankou Wetland)were selected as research specimen.The vegetation structure characteristics(including the abundance of plant species,amount of total biomass and biological diversity)were investigated,and the pollution(total suspended solids(SS),total nitrogen(TN),total phosphorous(TP),ammonia nitrogen(NH3-N),nitrate(NO3-N)and chemical oxygen demand(COD)eliminations entering the lakes were quantitively monitored,and at the meantime the hydrological characteristics in the areas(flow velocity,flow rate,temperature and pH)were recorded.As a result,the water purification efficiency data has been further obtained,and by combining with the investigation of the typical plant communities and related natural ecological elements,the current study compared the water purification efficiencies of the five selected wetlands to explore the key ecological factor that determines the purification efficiency of the ecological remediation wetland,and to further supporting the wetland design and layout for plateau lakes in central Yunnan area and even the whole province.The findings through the current study are listed as the following,(1)The SS and COD elimination rate of the five selected wetlands can be arrange as Nankou Wetland>Laojiugou Wetland>East River Wetland>Laoyuhe Wetland>Baiyuhe Wetland,with the elimination ranges of 5.78%-40.55%and-1.5%-41.32%,respectively;the TN,TP,NO3-N elimination rate can be arranged as Nankou Wetland>Laoyuhe Wetland>Laojiugou Wetland>East River Wetland>Baiyuhe Wetland,with the elimination ranges of-17.28%-43.68%,-8.49%-33.45%,and 4.69%-52.39%,respectively;the NH3-N elimination rate can be arranged as Laoyuhe Wetland>Nankou Wetland>Laojiugou>Wetland East River>Wetland Baiyuhe Wetland,with the elimination range of 3.92%-49.16%;(2)regression analysis shows,the flow velocity is the key determining factor of SS elimination rate,the interpretation ratio to the SS elimination reached-1.379,and the model fitting degree is 0.496;the flow velocity,plant diversity and abundance are the key determining factors of TN elimination rate,the interpretation ratios to the TN elimination reached-1.162,0.444,and 0.506,respectively,and the model fitting degree is 0.681;the plant abundance and pH are the key determining factors of TP elimination rate,the interpretation ratios to the TP elimination reached 0.555 and 0.290,respectively,and the model fitting degree is 0.587;the flow velocity,pH,plant abundance and biomass are the key determining factors of NO3-N elimination rate,the interpretation ratios to the NO3-Nelimination reached 0.935,0.608,0.326 and-0.367,respectively,and the model fitting degree is 0.682;the flow velocity,plant diversity,biomass,plant abundance and pH are the key determining factors of NH3-N elimination rate,the interpretation ratios to the NH3-N elimination reached-0.608,0.591,0.562,0.421 and-0.209,respectively,and the model fitting degree is 0.861;the flow velocity is the key determining factor of COD elimination rate,the interpretation ratioto the COD elimination reached-1.576,and the model fitting degree is 0.272.In conclusion,under the different plant patterns(plant abundance,biomass and plant diversity)and the hydrological characteristics(flow velocity,flow rate,temperature and pH),the purification efficiencies of wetlands vary significantly.