Study On Immobilization Of Co-contaminated Soils By Heavy Metal Using Clay Mineral

The main research contents in this experiment are that an outdoor pot-culture experiment was carried out to study the effects of different kinds of amendments(clay minerals, modified clay minerals, phosphates and so on) treatments on immobilization of cadmium (Cd) and lead (Pb) co-contaminated soils collected from Daye County, Hubei Province.We do the research including plant growth,Cd and Pb uptake in B. Chinensis,Speciation analysis of soil Cd,pH value and available Cd and Pb concentration,forthmore,we find the relation between the Cd and Pb concentration of B. Chinensis with pH value,available Cd and Pb concentration, the main conclusions are following:1.From treatment of single clay mineral ,sepiolite could significantly promote growth of Brassica Chinensis; and sepiolite treatments could not only decrease Cd and Pb concentration of B. Chinensis but also increase pH value remarkably,so the single sepiolite treatments is the most effective treatment for immobilization of Cd co-contaminated soils.2. The results from the compound treatment of sepiolite and sepiolite (lime) show that the compound treatment have the more effect in yield and significantly decreasing concentration of Cd than the single sepiolite,in addition, in terms of economic and Passivation effect the level of 6% is more appropriate to be applied . Both the compound treatment and the single sepiolite can improve pH value,but the acid-modified sepiolite treatment cann't; all treatment markedly decrease concentration of Cd, the compound treatment of sepiolite and phosphate appeared more efficient than the single.in summry, the compound treatment of sepiolite and phosphate the compound treatment of sepiolite and phosphate is the most effective treatment for immobilization of Cd co-contaminated soils.3. We further studied immobilization of the compound treatment of sepiolite and phosphate in the Pb-Cd contaminated soil,the results showed that the compound treatment of sepiolite and phosphate could markedly increase dry biomass of shoots and roots,and make the shoot concentration of Cd and Pb reduced,and the single phosphate have the better efficient than others in reducing the shoot concentration of Cd and Pb ,and the decreasing effect of sepiolite treatment on Cd and Pb concentrations of B. Chinensis was the worst. All amendment treatments could significantly increase the pH values of soils. Most of amendment treatments could markedly reduce available Cd and Pb concentrations of soils. In summary, the compound treatment of sepiolite and phosphate is the most effective treatment for immobilization of Cd and Pb co-contaminated soils.