The Effect Of Combined Application With 4A Zeolite And Chicken Manure On The Immobilization Remediation Of Cadmium Contaminated Soil

Cadmium is one of the most typical and serious elements in soil heavy metal pollution,which not only brings serious harm to agricultural production,but also poses a great threat to food safety and human health.Based on the technology theory of cadmium contaminated soil immobilization remediation,in this study the soil cadmium adsorption desorption experiment and simulation of pollution pot experiment were conducted to explore the effect of 4A zeolite,chicken manure and their combination on remediation of cadmium contaminated soil,finally in order to screen the best combination of the passivator and find 4A zeolite and chicken manure immobilization repair mechanism of cadmium contaminated soil.The main results were as follows:1.The application of 4A zeolite and chicken manure could enhance the soil Cd²⁺adsorption capacity and reduce the soil Cd²⁺ desorption capability.The combined application of 4A zeolite and chicken manure soil Cd²⁺ adsorption capacity was higher than their single application,but the soil Cd²⁺ desorption capacity was less than their single application,in which the combined application of high amount of 4A zeolite(5g·kg^-1)and high amount of chicken manure(20g·kg^-1)soil Cd²⁺ adsorption capacity and rate were the highest,but soil Cd²⁺ desorption capacity and rate was the lowest so that the Cd²⁺ immobilization effect was the best.2.The application of 4A zeolite and chicken manure decreased the soil available Cd content by 16.20%-63.55%,increased Cd content of the other three forms in different degrees.The effect of combined application of 4A zeolite and chicken manure on soil Cd availability was significantly better than their single application.The changes of soil physical and chemical properties?pH,OM and CEC?of 4A zeolite and chicken manure were correlated with the changes of soil Cadmium speciation.3.The effect of combined application of 4A zeolite and chicken manure on lettuce biomass increase was significantly better than their single application in which the combined application of high amount of 4A zeolite(5g·kg^-1)and high amount of chicken manure(20g·kg^-1)were the highest growth group.4.The effect of combined application of 4A zeolite and chicken manure on reduction of Cd absorption,enrichment and migration were better than the single application in lettuce.The high amount of 4A zeolite(5g·kg^-1)+ the high amount of chicken manure(20g·kg^-1)made the Cd content of edible parts of lettuce lower than the international standard safety limit value 0.2mg·kg^-1?GB2762-2005?,therefore this combination can reduce the bioavailability of cadmium best.5.The effect of combined application of 4A zeolite and chicken manure on soil pH and CEC was better than that of single application,and the effect on soil organic matter was slightly weaker than single application of chicken manure.Soil pH and CEC were significantly positively correlated with soil Cd²⁺ adsorption capability and were significantly negatively correlated with the soil available Cd content and the enrichment and migration ability of Cd in lettuce.Therefore,the combined application of 4A zeolite and chicken manure mainly through the improvement of soil pH and CEC in order to achieve the purpose of immobilization repair of cadmium contaminated soil.