Formation And Explosion Mechanism Of Delayed Geochemical Hazard Of CD Elements

Heavy metal is one kind of persistent toxic pollutants, which can be enriched in organism and soil and lead to potential hazard. Therefore, research on the changing regularity of heavy metals in the soil, can be taken as the basis for the corresponding preventive measures to prevent the proliferation of heavy metals. The kinetics of adsorption and desorption of Cadmium, and factors on the Cadmium absorption and desorption process were discussed. The mainly objectives of the present studies were to analyse form transformation of Cadmium in the soil. Migration patterns of Cadmium in the soil were discussed through the soil column simulation experiment.According to adsorption and desorption experiment, Cadmium adsorption quantity largen when the liquid adsorption concentration increases. While the concentration of absorption liquid reaches80mg-L-’, the value of adsorption quantity no longer changes and becomes a constant value. Langmuir equation is the most optimal equation which can be described the Isothermal adsorption. Elovich equation is the most optimal Cadmium adsorption-desorption kinetics equation which can reflect the two stages of soaring phase and stationary phase. Adsorption amount of Cadmium is positive correlated to pH, organic matter of soil, and pH of adsorption liquid, and release amount is negatively correlated to pH, organic matter of soil. Besides, the soil pH value is the main influence factor.Exchangeable form is the main distribution and the easiest desorption form in the soil, carbonate, Mn oxide-occluded and organically bound forms are more prone to high organic matter and high pH value soil. When pH of soil is above4.23, a part of Exchangeable transform into Mn oxide-occluded and organically bound. High organic content of soil prevents exchangeable form desorbing, but it is beneficial for exchangeable form transforming into other forms. After extracting exchangeable form, other forms will rapidly transform into exchangeable form in a short time. The transformation in the first extraction is more easily than that in the second one, the form distribution proportion is closer to former extraction.In the soil column experiment, Cadmium is tending to stable adsorption in the surface soil whose depth is0-20cm. Cadmium in soil is not easy to move vertically under the effect of rainfall. Even in the alkaline soil with high concentration of Cadmium, the Cadmium concentration in the leached liquid will not exceed national standard of soil environment.