Effect Of Cadmium-resistant Bacteria And Soil Colloids On Cadmium Bioavailability In Soils

Cadmium-resistant bacteria were selected from heavy metal contaminated soil in a mining area, three colloids of Red soil, Lateritic red earth and Brown calcareous soil were extracted, to research cadmium-resistant bacteria's effect on cadmium adsorption in different soil colloids. Transformation of Cd forms adsorbed by complex of cadmium-resistant bacteria and soil colloids was studied. Then Lolium multiflorum was used for a pot experiment, to research the effect of cadmium-resistant bacteria on cadmium's biological effectiveness on Lateritic red earths and Brown calcareous soil. The main conclusions are as follows:1.Cd adsorption capacity of three soil colloids increased with Cd concentrations' increasing.On the whole, adsorption capacity of three soil colloids was:Brown calcareous soil>Lateritic red earth>Red soil. Cd adsorption capacity of three soil colloids all increased obviously, with cadmium-resistant bacteria inoculated. And Cd adsorption capacity of Red soil increased most obviously.2. Cadmium-resistant bacteria reduced content of wake acid soluble Cd form and residual Cd form, enhanced content of reducible Cd form and oxidable Cd form. With Cadmium-resistant bacteria inoculated, content of Cd forms on Lateritic red earth colloid and Red soil colloid presented as:residual form>wake acid soluble form>reducible form>oxidable form. However, content of Cd forms on Brown calcareous soil colloid presented as:reducible form>residual form>wake acid soluble form>oxidable form.3. In Lolium multiflorum pot experiment, cadmium-resistant bacteria enhanced the biomass of both underground part and overground part of Lolium multiflorum, made Cd activated in soil, reduced content of wake acid soluble Cd form and residual Cd form, enhanced content of reducible Cd form and oxidable Cd form. And it promoted Cd in soil to move into Lolium multiflorum. In general, cadmium-resistant bacteria enhanced cadmium bioavailability in soils.4. On Lateritic red earth, correlation between Cd content in Lolium multiflorum and reducible Cd form in soil was extremely significant, between Cd content in Lolium multiflorum and oxidable Cd form was significant. On Brown calcareous soil, correlation of Cd content in Lolium multiflorum and oxidable Cd form in soil was extremely significant.