The Mechanism Of Restored Wetland On Regulating Exogenous Nitrogen Input And The Study On Its Demonstration Projects

Wetlands represent one of the most productive ecosystems in the word,but it has been severely damaged by the double effects of violent artifical disturbance and natural erosion.Now people has gradully realized the importance of wetlands and bulit lots of restored wetlands.Vast amounts of nitrogen input will bring pollution to estuarine waters,lakes and other water quality.The restored wetland locate around eutrophication waters littoral had special function in removing high exogenous nitrogen and at the same time provided habitat for local anmial in the form of vegetation.However,the human assitant restored wetlands had special function in removing high nitrogen in water.We focused on the mechanism of restored wetland on regulating exogenous nitrogen input and research on the nitrogen removal mechanism when keep wetland matrix-water interface still and mix wetland matrix-water.And we disscussed the degradation efficiency of nitrogen under simulated tidal stream in the laboratory and restored wetlands in situ.In order to further illustrate its regulatory,we combined the running monitoring data in two typical compound ecological restored wetlands.In the pilot-scale test of the degradation efficiency of nitrogen of wetland substrate,both with additional carbon source,the results shows that under the mixed condition the removel rate of TDN reached 0.68g N/m²·d,as well as the denitrification efficiency in matrix-water interface received a significant boost under the still condition.By ¹⁵N stable isotope technique in the two groups with and without additional carbon in the matrix-water interface,we concluded that the process of dissimilatory nitrate reduction to ammonium（DNRA）account for 12.6%and 17.4%of the total amount of NO₃^--N removal,respectively.We make a futher study on the degradation efficiency of nitrogen by restored wetland in situ experiment.Under simulated tidal stream（all groups with Phragmites）,the results demonstrate that the TDN removal rate reached 0.70gN/m²·d in the porewater of high nitrogen and additional carbon group.This removal rate is 4.7 times higher than the nitrogen and without additional carbon group in the water,and 2.8 times higher than the high nitrogen and with Phragmites group in the water in the removal nitrogen experiment in situ,and 1.6 times higher than the high nitrogen and with out Phragmites group in the overlying water in the removal nitrogen experiment in situ.The results of field demonstration projects display that the two restored wetlands engineering area have a stable fuction of water quality purification and resistance to interference.The TN removal rate is0.04gN/m²·d for low nitrogen water in the restored coastal wetlands,but ecological front library boost the TN removal rate to 0.06gN/m²·d when high nitrogen water entering into the restored wetland.The phenomenon of the increase of NH₄⁺-N concentration were both observed in the waterscape restored wetland and coastal wetland.We consider that both have in common is that they are laid with gravel,which may help the DNRA process.