Study On Nitrogen Adsorption And Release Of Wetland Soils In The Nanjishan Nature Reserve Of Poyang Lake

Wetland is important ecosystem and environment in globe.Its purification for nutrient from the water flow can relieve the water eutrophication,which are the results of the excess of nitrogen and phosphorus.Analyses were carried out by using the methods which connect real sampling sampling with Laboratory simulation to measure the physical and chemical characteristics,the speciation and the contents of nitrogen in Nanjishan wetland nature reserve.It provided a scientific basis for biogeochemical circulation of this area.The adsorption and desorption of nitrogen and the environmental factors had been also discussed in this paper.The results of the research ascertained the maximum adsorption of nitrogen by soil.The results provided a scientific basis for eutrophication controlling in Poyang Lake and it has important theoretical value for the sustainable development of the Poyang Lake wetland.The results were summarized as follows:(1) The samples of soil in Nanjishan nature reserve were of light acidity.The distributed range and average value of the content of pH value in soil samples were 5.18～6.04 and 5.71 respectively.The distributed range and average value of the content of the organic in soil samples were 0.81%～3.83%and 1.32%respectively. The average value of the total phosphorus,total sulfur,total carbon and the carbon and nitrogen ratio were 477.36 mg/kg,1909.29 mg/kg,6690 mg/kg and 1.35 respectively.The average value of the total nitrogen,ammonium nitrogen,nitrate nitrogen,available nitrogen and organic nitrogen were 4591 mg/kg,12.66 mg/kg,1.8 mg/kg,26.25 mg/kg and 4598 mg/kg respectively.The forms of nitrogen that we concerned were decreased from plow layer to subsoil in five paddy soil profile. Relevant analysis taken by SPSS showed that the forms of nitrogen had significantly correlated each other in plow layer.(2) The adsorption of NH₄⁺-N for the soil of Nanjishan was a complex dynamics process.In this paper,adsorptive characteristic of NH₄⁺-N on soil in Nanjishan were analyzed in laboratory.The results indicated that process of sorption of NH₄⁺-N on soil mainly occurred within 0～7 hours,and then reached a dynamic equilibrium.The maximum value of adsorption rate of NH₄⁺-N reached 14.04 mg/kg.h.The research of isothermal adsorption indicated that the NH₄⁺-N in the soil in Nanjishan had a good correlation with the Langmuir and Freundlich equations,especially,there was a significant correlation between the latter equation and the soil.According to the Langmuir adsorption equation,the maximum adsorption amount was 196.08 mg/kg soil,the adsorption constant was 0.45;MBC was 88.27 mg/kg soil.The adsorption was greatly influenced by environmental factors.The result indicated that,pH values had great influence on the sorption of NH₄⁺-N,with the sorption ability increasing gradually as the increasing pH values and as the increasing of the water and soil ratio. High concentration of ion and temperature restrained NH₄⁺-N.(3) The adsorption and desorption were reciprocal processes.NH₄⁺-N that adsorbed could release inversely.The desorption amount of NH₄⁺-N in soil increased with the adsorbed amount.In this paper,desorption characteristic of NH₄⁺-N on soil in Nanjishan were also analyzed in laboratory.The result indicated that it reached equilibrium after 12 hours,the maximum value of desorption rate of NH₄⁺-N reached 3.47 mg/kg.h.The desorption amount of NH₄⁺-N in the soil were mainly from the beginning of the process,and the process of desorption was very slow.The results provide a scientific basis for the in-depth study of nitrogen loss in soil.