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

Organic and inorganic phosphorus forms (includeing Sol-P, Al-P,Fe-P,Obs-P and Ca-P) of wetland soil taken from Nanjishan Nature Reserve in Poyang Lake, the phosphorus adsorption and release properties of the soil were studied through laboratory imitation.The results showed that:Organic phosphorus was found to be the major component of the total phosphorus. In inorganic phosphorus ,the content of O-P was highest in each soil layer.The content of organic phosphorus and Fe-P decreased with the increasement of soil depth, all the phosphorus forms were influenced significantly by pH.The phosphorus adsorption on the soil mainly occurred within 0~6 h, and then reached a dynamic equlibrium.The dynamic curve of phosphorus adsorptin can be described with the Elovich and the first equation, and the phosphorus isothems were fit in well with Freundlich Langmuir and Tempkin equations. The maximum amount adsorption and adsorption constant can be calculated from the Langmuir equation, and they were correlated with physical and chemical characters of soils. Furthermore, the correlation between environmental factors and phosphate adsorption was presented in this experiment, including the ratio between soils and solution, pH and Ca~2+ concentration, organic anion and temperature. Phosphorus adsorption-desorption equilibrium concentration was different on different soils. Due to the values of some soils were higher than the threshold concentration of eutrophication, they had the risk of phosphorus release from them when flooded.It is recommended that phosphorus adsorption indices can be used to estimate the maximum amount adsorption and the phosphorus adsorption saturation degree can be used to evaluate the transfer capability of phosphorus at the soio-water interface.With the time passing by, the amount of phosphorus release from the soil was increased, then reached a dynamic equlibrium after 24 h, and the amount was limited. The process of phosphorus re-release after adsorbing a large amount of phosphorus was slow. The amount of phosphorus release increased with rising the temperature and pH and disturbing the water. The amount of phosphorus release in anaerobic was more than in aerobic. Research also showed that different phosphorus forms in soils were related to the amount of phosphorus release in varing degrees. The dissolved phosphorus, Fe-P and Al-P played the most important roles.