The Remediation Of Cadmium Contaminated Soil By Nanomaterials,Alfalfa And Rhizobia Composite System

Soil heavy metal pollution has seriously threatened the ecological environment and human health, and the remediation technology of soil heavy metal pollution has significance. This paper selects the most serious Cadmium contaminated soil as objective, and selects the hydroxyapatite nanoparticles, ferric oxide nanoparticles, alfalfa and S. meliloti CCNWSX0020 as soil remediation agents. This paper forms a nanometer materials, alfalfa and rhizobium complex system by combining chemical remediation and bioremediation remediation together. Analyse and compare the influence of different materials and systems on Cadmium content of plant, Cadmium content of soil and the change in the different forms of Cadmium, In order to obtain efficient and environmentally friendly remediation of soil Cadmium pollution. The results are as follows:In TY medium, different nanomaterials have great influence on the growth of rhizobium.When the concentration of nano-hydroxyapatite was 0.5 g / 100 ml, the number of living rhizobium reduced by 12.92%. When the concentration of nano-Fe2O3 was 0.5 g / 100 ml, the number of living rhizobium reduced by 43.80%. By comparison, the influence of Fe2O3 nanoparticles on rhizobium was far higher than the influence of hydroxyapatite nanoparticles.In Pot plant experiment, With the increase of Cadmium in the soil, the plant height, root length, number of nodules and dry weight of alfalfa showed a downward trend. The higher Cadmium concentration increased, the greater the impact on alfalfa. Under the low concentration of Cadmium, S. meliloti CCNWSX0020 can obviously increase the number of nodules in alfalfa. However, when the concentration of Cadmium attained to 40 mg/kg, the effects of inoculation was not significant.Nano hydroxyapatite,alfalfa and rhizobium composite system can effectively reduce the total Cadmium content in the soil, reducing the total Cadmium content in soil by 16.57%.The composite system also can decrease the effective state of Cadmium by 35.04%, and translated them into the residual state of Cadmium which creatures can not use,and then the toxicity of Cadmium to the organism is alleviate obviously. In addition, the content of Cadmium in the alfalfa leaves and stems also significantly reduced by 17.46%.Nano-Fe2O3, alfalfa and rhizobium composite system can effectively reduce the total Cadmium content in the soil, reducing the total Cadmium content in soil by 14.93%.The system significantly reduced the effective state of Cadmium by 33.79%. In addition, the content of Cadmium in the alfalfa leaves and stems also significantly reduced by 20.11%.