Screening Of Nitrifying Bacteria And Their Role Of Nitrification In Sediments Of Estuarine Wetlands

This essay takes the wetland sediments of the Pearl River estuary as the research object, byseparating, purifying and concentrating the indigenous nitrifying bacteria in the sediment,acclimating them to adapt to high salinity and combining the indigenous nitrifying bacteria withwetland salt-tolerant plants, thus examining its nitrification property under the environmentalcondition of estuarine water, and laying the foundation of mitigating nitrogen pollution inestuarine waters caused especially by the salt tide intrusion as well as the repair after intrusion.The results show that the number of nitrifying bacteria per gram contained in sediments fromreeds wetland, Spartina alterniflora wetland and mudflat wetland, which are the three typicalwetlands, are respectively2.1×10⁵cells/g,1.8×10⁵cells/g and0.5×10⁵cells/g. The net nitrificationrate are respectively0.41±0.02mg·m^-2·d^-1,0.35±0.03mg·m^-2·d^-1,0.12±0.02mg·m^-2·d^-1.The nitrification efficiency in the reed wetland area is higher than that of the Spartina alterifloraarea, and efficiency in the mudflat wetland area appears to be the lowest.A L4bacterial strain that has the best overall efficiency is selected from sediments in reedwetlands which possess excellent nitrification property within0‰to20‰salinity, and theaverage nitrification intensity is80.9%.When the temperature reaches30℃, pH equals7.2, thehighest nitrification efficiency is81.3%. Bacteria strain L4is identified as Nitrosomonascommuni.To further enhance the nitrification efficiency under high salinity, the researcher combinesL4strains with reed plants, thus forming the reed-L4strain combination system. Under varioussalinity conditions simulating the salt tide intrusion in the Pearl River estuary, the combinationsystem manifests certain degree of synergy within30‰to40‰salinity. After7days'cultivation, the ammonia nitrogen processing efficiency of the reed combination system arrivesat47.5%and26.2%as the salinity is respectively30‰and40‰, greater than38.1%and7.7%,which are the adding efficiency of sole reed and L4strain.Salinity and hydrodynamic conditionsare significant impact factors for nitrification.