Adsorption Of Cadmium Onto Sediments Of Hydro-Fluctuation Belt In Three Goerge Reservoir And Its Potential Influence On Water Pollution

The Hydro-Fluctuation Belt in Three Gorges Reservoir is a complicated system, it is the connection between land and water areas. For natural and artificial reasons, the ecological system of the reservoir turns to be fragile and instable. In the flooding period, the sediment on Hydro-Fluctuation Belt can be considered as the sediment on the river bed.However, due to the disturbance by humanity, allogenic materials, and the seasonal changes of reservoir water line, there could be some difference between them. This paper investigated the content and distribution of 6 kinds of heavy metal element (Cu, Zn, Pb, Cr, Cd, Ni) on Xiao Jiang River,based on which it analyzed the adsorption of Cadmium onto the sediments on Hydro-Fluctuation Belt.Results are as follows:The average content of heavy metals in study area:Cd 0.387mg/kg; Cr 57.196mg/kg; Cu 28.685mg/kg; Ni 27.910 mg/kg; Pd 35.567 mg/kg; Zn 126.028 mg/kg. Accord-ing to the single-factor pollution assessment method,the average fouling index of Cd, Zn, and Pb were separately 1.935,1.26 and 1.016.The simulated experiment on Cadmium adsorption showed that:Adsorption of heavy metals onto sediments is closely related to its fraction, strength and rate of the adsorption are increasing with the decreases of fraction. The adsorption process can be devided into there phases:Phase of rapid growth, gradients, and homeostasis.the kinetics of adsorption exhibited Lagergren the first order kinetic equations. The second order kinetic equation can't be applied.By studying the influence of temperature on adsorption of cadmium ions, we found that the adsorption process is an endothermic reaction, the adsorption kinetics increased with temperature rise. n the experimental conditions, the adsorption includes both moleCular adsorption, and ion exchange adsorption. The thermodynamic parameters indicated that the adsorption process is a spontaneous endothermic reaction, and with the temperature increasing, the degrees of freedom increases. This indicates that flooding period, low level of water temperature conducive to the desorption process. The adsorption of cadmium onto sediments on Hydro-Fluctuation Belt comply with the Langmuir and Freundlich models, and the coefficient with the Freundlich model were higher, indicating that the latter can describe the sediment Cadmium ion adsorption isotherm more accurately.In condition of stable temperature, pH, and other conditions, singlely changing the initial concentration of the sediment, it was found that the adsorption showed solid concentration effect, which appeared that adsorption density increased with the increase of initial concentration of sediment.It can be explained by MEA theory.