Research On Characteristics Of Four Strains Of Ammonia-oxidizing Bacteria In Estuary Wetlands

At present, Liaohe estuary reed wetland, which has a strong ecosystem servicefunction, is the largest coastal estuary wetland in China. It not only could conservepurify drinking water, afford wildlife habitats and adjust the atmospheric componentsand so on, but also could remove ammonia nitrate and other organic pollutants,helping to promote wetland nitrogen cycle. Nitrogen was one of the most limitedelements of primary production processes and Plant Photosynthesis processes interrestrial ecosystems. Generally inorganic nitrogen content in wetland sediment weremaintained at a relatively low level, so it was usually the most important limitingnutrients. Nitrification of nitrifying bacteria in wetland sediments was an importantpart of nitrogen biogeochemical cycles. Researches of nitrogen cycle bacteria hasbeen concentrated mostly on sewage processor and activated sludge, etc,, however,less work has been done on the nitrogen cycle bacteria in soil，especially on those inthe wetland soil. Therefore, the study of wetland nitrifying bacteria has greatsignificance to explore wetland eco-system productivity and nitrogen interfaceprocesses, and reveal the wetland nitrogen biogeochemical behavior and its ecologicalsignificance.In order to understand the role of nitrifying bacteria in pollution purification andnitrogen cycle in Liaohe estuary reed wetland sediments, and further offer referencesfor ecological microbial remediation and management of Liaohe wetland estuary, thispaper combines the method of spot investigation training with the method oflaboratory simulation training to discuss the characteristics of nitrifying bacteria inLiaohe estuary reed wetland sediments. Efficient ammonia oxidizing bacteria weregained through the traditional laboratory simulation training method, first Microbialenrichment training, and then separation screening bacteria from Liaohe estuary reedwetland sediments. This study analyzed the characterizations and nitrification of theammonium oxidation bacteria (ammonia-oxidizing bacteria, AOB) by the control experiments using single-factor analysis method. Ammonia concentration, salinity,temperature, PH，organic matter and petroleum hydrocarbon content were selected tobe the main environmental impact factors. The number of AOB was determined bythe method of MPN-Griess. And the relationship between nitrification of AOB andenvironmental impact factors was analyzed by regression analysis and correlationanalysis of SPSS13.0software. The results showed as follows:From Liaohe reed wetland sediment, suspension of4efficient nitrifying bacteriawere obtained by enriched culture are a12, c1,2-2and c2-1respectively. Theammonia nitrogen removal rates reach a plateau at the14thd, above80%, obtainedfour efficient nitrite-oxidizing bacteria, respectively na1, nc1, n2-2, n2-1,and thenitrite nitrogen removal rates reach a plateau at the7thd, above98%.Ammonia nitrogen removal rates of the four AOB were affected by cultivationtemperature, pH, salinity, ammonia nitrogen concentration, organic matter content andoil content. Effects of these environmental factors on the four AOB were basically thesame. With the temperature increasing (15-30℃), the ammonia removal ratesgradually increased, the highest ammonia nitrogen removal rates and the bestnitrification results of the4experimental groups were obtained at about30℃, andthen decreased sharply when the temperature was above30℃. The ammonia nitrogenremoval rates increased at pH values over the range of5-7.5, then reached themaximum removal rates at pH values over the range of7.5-8, and then decreasedsharply when pH values were above8. Effects of salinity variation on nitrificationwere not significant at low salinity (5-10g/kg). Nitrification was significantlyinhibited at high salinity (15-20g/kg). When the initial ammonia concentration wasless than2g/L, the ammonia removal rates gradually increase as the ammoniacontent increase; when the initial ammonia concentration is greater than2g/L, theammonia removal rates decreased slightly. Organic matter content and oil contenthave inhibition effects on the ammonia removal rate, which increased with theconcentration of organic matter and oil.