Comparative Study Of Nitrification And Denitrification In Sediment Of Pearl River Estuarine Wetlands

The present study was explored the processes of nitrification and denitrificationoccurring in mangrove，phragmites and tidal flats areas of Pearl River estuarinewetlands．Resarch used the method of on-the-spot investigation and laboratory，theaim was to investigate；(i) the rates of nitrification and denitrification and theirenvironmental effects；(ii) analysis of total nitrogen and the form of transferablenitrogen．Results of research have shown that：The contents of total nitrogen and different forms of transferable nitrogen inPearl River estuarine wetlands，which was mainly influenced by terrigenous inputs，character of sediments and their environment． The content of nitrogen instrong-oxidant extractable form was the highest among all transferable nitrogen formsof different sediment．Different transferable had similar variation trend in differentgrain-size sediments，the SOEF-N contents were the highest among the four forms ofnitrogen；and the contents of WAEF-N were lower than those of SOEF-N；while werethe highest among the inorganic nitrogen；the contents of IEF-N were lower thanthose of WAEF-N and higher than those of SAEF-N.Besides the contents of all theforms of exchangeable nitrogen were the highest in fine sediments，while the lowestin coarse sediments．Therefore，fine sediments contain more different forms ofexchangeable nitrogen，that is the nitrogen could be enriched in fine sediments．The results indicated that the numbers of ammonia oxidizing bacteria(AOB)and denitrifying bacteria， its nitrification and denitrification all had spatialfeature．They had different variation trend in different moths，and the numbers ofAOB was most in December，lowest in September．But on the contrary, the numbersof denitrifying bacteria and denitrification was most in September， lowest inDecember. It showed that the number of bacteria keeps high relevance withnitrification and denitrification rate，so it was one of the important factors affectingnitrification and denitrification rate． The intension order of nitrification and denitrification of Pearl River estuarine wetlands in the same moths was mangrovearea，phragmites and tidal flats．This showed that plant benefited the occurrences ofnitrification and denitrification．Macrophyte was important on nitrogen cycle inestuarine wetlands．Temperature，salinity，pH，ammonia the concentration of nitrate concentrationwere important factors for nitrification and denitrification rate．The lower temperatureand higher salinity could inhibit the process of denitrification． The optimumtemperature and salinity for nitrification and denitrification was28℃，5‰．Thesuitable pH for nitrification and denitrification was about8.5，7.5，respectively．Andthe content of ammonia nitrogen could improve the growth of ammonia oxidizingbacteria．In certain circumstances，as the nitrate concentrations cut，the denitrifyingrate decreased. Through the comparison，we can conclude that when environmentalconditions changed，nitrification and denitrification of tidal flats large variationamplitude comparing mangrove area and phragmites of the variety range are higher．Itindicated that plant make estuarine had stronger adaptive capacity to environment．...