Effects Of Environmental Factors On The Community Structure Of Denitrification In Sediment Of Constructed Wetland

In recent years,pollution load of East Lake was increased year by year,the function of interception and removal has been reduced,the water quality of Erhai is facing a serious threat.Dali state government planned and constructed hundreds acres of constructed wetlands in “12th Five-Year”.In this paper,the research site is the Dengbeiqiao Erqi Constructed Wetland.The import and export of constructed wetland water quality was monitored for a year.The results showed that the removal rate of TN,TP,NH4+-N,NO3--N,CODMn can reach 20%~40%.The removal rate of pollutants was higher in spring and summer than in autumn and winter.Set 5 sampling points in the Dengbeiqiao Erqi Constructed Wetland,collect sediments of wetland in the rainy season,dry season and level period season,detect the physicochemical index of sediment,analyse 16 S r RNA V4~V5,nir S and nir K genes of the sediment with fluorescent quantitative PCR technology and high throughput technology,analyse the community structure and the composition of nir S and nir K genes.And analysis the relationship between the community structure and environmental factors.The experimental results show that the number of microorganisms in the constructed wetland changes constantly,the number of rainy season is greater than the dry season,most of the dominant bacteria in the sediment have the function of nitrogen and phosphorus removal.The number of nir S gene was significantly higher than the number of nir K genes for 2 orders of magnitude(P<0.05),which is due to long-term hypoxia.The rainy season abundance was significantly higher than the dry season abundance(P<0.05),which is related to the temperature of sampling,rainy season is more conducive to microbial reproduction.Proteobacteria in nir S and nir K in the denitrifying microorganisms are accounted for the largest,Micromonas and Methanoregula have been detected with nir K denitrification genes,this shows that in addition to bacteria,some eukaryotes and archaeas also have denitrification function.At 11.10~23.40 ?,the temperature was positively correlated with nir S denitrifying microorganism abundance and diversity was negatively correlated.When the environment was weak alkaline(7.60~8.25 p H),p H and the abundance of nir S denitrification microorganisms were significantly negatively correlated,and the diversity was significantly positively correlated.When the concentration of NO3--N in the sediment was between 0.32~42.46 mg/kg,there was a significantly positive correlation between NO3--N concentration and the number of nir S denitrifying microorganisms,and there was a significantly negative correlation between NO3--N concentration and the diversity of nir S denitrifying microorganisms.There was a significant correlation between TN and TP on the OTU of nir S,this also shows that the change of nir S in the environmental gradient is more obvious than nir K.