Anaerobic Ammonia Oxidation Process And Mechanism Of Chongming Tidal Flat

With the development of the human society, due to large number input of N to estuarine areas, eutrophication (red tide) is particularly serious, causing estuarine wetlands periodic or permanent hypoxia, hypoxia phenomenon, further leading to the gradual degradation of wetland functions, ecologicalsystem structural damage. It has become a hot topic of social concern about the nitrogen cycle and the impact mechanism. It plays significant role in the evolution of the process of eutrophication and prevention measures to have profound understanding of the inorganic nitrogen cycle in the ecosystem. Anaerobic ammonium oxidation process in the natural environment is widespread, which has been found for the first time since the end of the last century by a Dutch researcher, then a Canadian researcher confirmed the presence of anaerobic ammonia oxidation in the natural environment, and the anammox process in the oceans, lakes, wetlands and other ecosystems were also found. It is an extremely important supplement for the process of biogeochemical cycling of nitrogen, and also changed the traditional concern on the nitrogen removal. In the last decade, the anammox process had been drawn great attention.Chongming tidal flat locate at the entrance of Yangtze River, is a complete developed wetland ecosystem, and play a significant effect on study of the estuarine area for its unique geographical location and ecological environment. The spatial and temporal characteristics of the anaerobic ammonium oxidation rate along salinity gradient were analyzed, anaerobic ammonium oxidation rate of different vegetation types, as well as the effect of many environmental factors on naerobic ammonium oxidation rate were also explored. These studies provide some basic data and scientific basis for further study on N cycle process of Chongming tidal flat.There is a significant spatial and temporal characteristics of anaerobic ammonium oxidation rate in Chongming tidal flat and its seasonal variation were as follows:summar＞autumn＞spring＞winter; The anaerobic ammonium oxidation rates of sea Scripus mariqueter were highest on annual average, Spartina alterniflora loisel followed and the surface of Phragmites rhizosphere were minimum among different vegetation types. Anaerobic ammonia oxidation rates with the tidal flat topography unit distribution were middle tidal tidal flat> low tidal tidal flat> high tidal tidal flat; Judging from the overlying water salinity, the anaerobic ammonium oxidation rates had signicant difference, maximum occurred at freshwater area, mix transition zone followed and minmum at sea water area.The profile of anaerobic ammonium oxidation rate of Chongming tidal flat salt marsh vegetation rhizosphere had great spatial and temporal differences:Spartina alterniflora rhizosphere have the highest anaerobic ammonia oxidation rate on annual average, Scripus mariqueter followed and Phragmites astralis rhizosphere have the lowest rate. Judging from the tidal flat topography unit distribution, due to the diversity and abundance of tidal flat anaerobic ammonium oxidizing bacteria, the middle tidal flat anaerobic ammonia oxidation rate were highest on annual average. In addition, due to relatively long exposure time and high sediment oxygen restrict the anammox process, the rate is much lower.Anaerobic ammonia oxidation rate in the Chongming tidal flat rhizosphere sediments showed that the spatial and temporal differences were mainly controlled by the temperature, salinity and sediment Fe2+, NO3-, etc. The temperature simulation experiment showed that the optimum temperature of the anaerobic ammonia oxidation process is about37℃. The sediment Fe2+, NO3-play inhibition effect on the anaerobic ammonia oxidation process. Multiple linear regression analysis between anaerobic ammonium oxidation rate and environment factors showed as follows:anaerobic ammonium oxidation rate of Phragmites rhizosphere mainly influenced by the soluble salt and ammonia; Spartina alterniflora loisel rhizosphere were impact by Fe3+, sulfide and the soluble salt; Scripus mariqueter rhizosphere were controlled by reduced Mn and organic carbon; middle tidal flat without vegetation area were influenced by NH4+, NO3-and reduced Mn; low middle tidal flat without vegetation area were impacted by Fe3+; The positive correlation coefficient between anaerobic ammonium oxidation rate and Fe3+was found, showed Fe3+was beneficial for anaerobic ammonium oxidation process.The nitrogen contribution rate of the Chongming tidal flat sediment ranged from0.46%-14.3%, and total amount were219.2-4323.1N nmol-g-1·yr-1. The results reflected that anaerobic ammonium oxidation process was an important way for nitrogen cycle and ecological environment effect was particularly significant. The nitrogen contribution rate of Chongming tidal flat wetland were ranged from0.46%-14.3%, and indicated that anaerobic ammonium oxidation process plays an essential role in nitrogen removal of wetland ecosystems.