Study On Adsorption And Leaching Properties Of Paddy-Soil Heavy Metal In Suburb Of Hefei City

As an important way for increasing yield in agricultural production, fertilization also can accelerate remediation of contaminated soil by heavy metal. It has been showed that Phosphorous fertilizers can alter soil surface charge by acid radical, which influence metal ions sorption by soil.In this paper, paddy-soil heavy metal in Daxing and Yicheng which are the suburb of Hefei City has been taken as main researching objects,the transport characteristics of heavy metals in soil, the influencing factors and their effecting mechanisms were studied by comprehensive methods such as static isotherm adsorption experiment. Batch equilibration method was used in this experiment. Adsorption thermodynamics and isotherm of heavy metals in two typical soils were studied.Adsorption thermodynamics was carried out on adsorption properties and mechanisms of heavy mentals onto paddy-soil. The isothermal heavy metals absorption data obtained all fitted with:Langmuir and Freundlich equation.The results show that adsorption data of three heavy mentals onto two typeso f paddy-soil fitted well to the Langmuir and Freundlich isotherms. The negative of adsorption Gibbs free enegy changes in all the cases are indicative of the spontaneous nature,which show chemical sorption coexist with physical sorption and the values of adsorption entropy changes are positive.The effective factors on absorption of heavy metals in paddy-soil were also studied. The results showed that temperature and phosphate have effect on the absorption of heavy metals. The absorption quantity increased with phosphate. With temperature increasing, the Cd,Pb absorption increased. With temperature increasing, the Hg absorption decreased.To obtain the knowledge of the impact on the environment risks of acid rain and phosphate, an investigation was undertaken . As one part of the research , soil column experiments were conducted to understand the heavy metal transport behaviors in soil profile under reclaimed water leaching condition.In this paper ,the leaching behaviors of Cd,Hg,Pb,As in paddy-soils were studied,which can supply the scientific evidence of the risk of surface water evaluation.Under the experimental conditions,the processes of transferring and leaching ,and chemical fractionation of Cd, Hg, Pb, As affected by simulated acid rain and phosphate were investigated.The relation of different pH acid rain and pollution of Cd, Hg, Pb, As in soil was analysed.The effects of diverse chroma ion in phosphate on dissolution and release of Cd, Hg, Pb, As in soil were also studied.