Rehabilitation Of Cd-Pb Contaminated Soil By Mineral Fertilizer Combined With Rice Hull Biocharcoal

Decades of urbanization and industrialization in china have led to a considerable part of the agricultural soil has reached the level of heavy metal pollution.When the technology chemical passivation is used to treat contaminated soil,concentrating on the application of one kind of passivation material is common,which often leads to the deficiency of the treatment effects.In this paper,mineral fertilizers and biochar are combined to study their effects on remediation of contaminated soil.Relying on the project of"Research on the Technology and Method of Mineral Fertilizer for Farmland Soil Regulation and Heavy Metal Rehabilitation?Key?",we conduct the previous indoor adsorption experiment,the mid-term dynamic leaching experiment and the later pot experiment.it was found that combining the mineral fertilizer with the rice husk biochar has a better treatment result than just using mineral fertilizer or rice husk biochar,and the different ratios of the two will lead to different treatment effects.The main results of the paper are as follows:?1?Adsorption experiments show that:C700?prepared at 700°C?adsorbs Pb²⁺and Cd²⁺is best.The adsorption of Pb²⁺by C700 is slightly better than mineral fertilizer,but as for the adsorption effect on Cd²⁺,the mineral fertilizer is much better.The isothermal adsorption behavior of Pb²⁺on C700 is more consistent with the Freundlich isotherm adsorption model.The isothermal adsorption behavior of Cd²⁺by mineral fertilizers is more consistent with the Langmuir isotherm adsorption model.In the complex solution including Pb²⁺and Cd²⁺,the ability of rice husk biochar to adsorb Cd²⁺was inhibited to some extent.The combination of C700 and mineral fertilizer can enhance the adsorption of Cd²⁺and Pb²⁺In the complex solution including Pb²⁺and Cd²⁺.?2?Leaching experiments show that the composite formulation can make Cd-Pb in the whole leaching process smoother and less leached.For the total leaching amount of Pb and Cd,the two groups of C3K7?74.6%lower than the blank group?and C7K3?72.8%lower than the blank group?have less leaching amount of Pb;the total leaching amount of Cd was deeply affected by minerals,the more mineral fertilizer is added in the formula,the more the total amount of Cd is leached.the two groups of C10K0?50.2%lower than the blank group?and C7K3?13.4%lower than the blank group?have less leaching amount of Cd.?3?In the pot experiments,just adding mineral fertilizer would cause Pb in the root soil to migrate from the reducible state to the oxidizable state.just adding mineral fertilizer has little effect on the weak acid-dissolved Cd in the root soil in the long-term pot experiment,which promote the migration of Cd from the oxidizable state and the reducible state to the residual state in the root soil.While rice husk biochar promotes the migration of weak acid-soluble Cd to reducible state.After mineral fertilizers were compounded with rice husk biochar,the weak acid soluble or reducible Cd content decreased and the residual or oxidized Cd content increased.Mineral fertilizer can promote the growth of pakchoi,C1K2 group achieves the maximum promotion value,and gains 38.12%compared with the blank group.Adding mineral fertilizer alone could promote the absorption of heavy metal Pb to a certain extent,while the compound formula C2K1 group had the best effect on reducing the absorption of Pb,which was 24%lower than the blank group;all the formula groups reduced the absorption of Cd,and the formula group C1K2 group had the best effect on reducing the absorption of Cd,which was 38%lower than the blank group.Due to the different pollution degree of Cd-Pb in the collected soil,the passivation of Cd element should be emphasized.So the formula chosen is C1K2.Under this formula,the content of Cd-Pb in plant decreased by 9%and 38%and the growth of plant increased by 38.12%compared with blank group.This formula not only increases the growth of Chinese cabbage,but also deactivate the Cd-Pb in soil and reduced the accumulation of Cd-Pb in Chinese cabbage.