Stabilization Efficiency And Ecological Risk Assessment Of Heavy Metals In Soil By Humic Acid Compound Attapulgite

Today’s society is changing with each passing day and developing rapidly.While development has brought convenience to people,it has also brought damage to our earth’s environment.The soil environment is the first to bear the brunt.In recent years,there have been many major public hazards caused by heavy metal pollution at home and abroad,and the lives and health of the people have been seriously threatened.In response to such problems,soil heavy metal pollution has gradually become a major research focus in environmental governance.At present,the technical means for soil remediation by adding a series of chemical amendments to heavy metal contaminated soil is gradually becoming mature.At present,attapulgite,which is cheap,large in quantity,and can effectively passivate metals in the soil,is one of the current effective improvement materials.In this paper,humic acid and attapulgite are used for compounding.The mass ratios of humic acid and attapulgite are 1:3,1:4,1:5,1:6,1:7,0:1.The passivation materials according to the ratio are mixed into artificially simulated heavy metal contaminated soil in equal amounts,and the physical and chemical properties of the soil,the content of Cd bioavailable state and the chemical form content of the soil are measured 30 days after the passivation.After the soil was inactivated,corn was used as the test plant for pot experiment,and it was harvested after growing to a certain extent.The biomass of corn seedlings,the content of heavy metal Cd above and below ground,and the enrichment and transport coefficient of heavy metal Cd of corn seedlings were measured.The experimental results are as follows:（1）The addition of passivation materials with different ratios has a significant impact on the physical and chemical properties of the soil.As the proportion of attapulgite in the passivation materials increases,the p H is gradually increasing,and the cation exchange capacity is gradually increasing.When the ratio of humic acid and attapulgite is 1:5,the soil conductivity is the highest,which is 11.70%higher than that of the control group.Soil organic matter increases with the increase of the ratio of humic acid,and the organic matter reaches the maximum when the ratio of humic acid to attapulgite is 1:3.（2）The humic acid compound attapulgite passivation material can reduce the biologically effective state of Cd in the soil in different cities.When the ratio of humic acid to attapulgite is1:5,the CaCl₂-Cd extraction state in the soil,The content of DTPA-Cd extraction state and TCLP-Cd extraction state reached the lowest level,respectively 1.57mg/kg,5.54mg/kg and3.42mg/kg,which were reduced by 34.03%,26.62%and 43.66 respectively compared with the control group.%.（3）The humic acid compound attapulgite passivation material significantly promotes the transformation of the heavy metal Cd in the soil from the weak acid extraction state to the residue state.When the ratio of humic acid to attapulgite is 1:5,the Cd rate The weak acid extraction state decreased the most,compared with the control group,decreased by 34.10%,and the reducible state and residue state of Cd increased the most,compared with the control group,increased by 21.09%and 63.13%,respectively.（4）The humic acid compound attapulgite passivation material can significantly increase plant biomass,improve plant growth indicators,and can reduce the accumulation,enrichment coefficient and transport coefficient of heavy metal Cd in plants.Compared with the control group,the length of the above-ground part,the length of the underground part,the fresh weight of the above-ground part,the fresh weight of the underground part,the dry weight of the above-ground part,and the dry weight of the underground part increased by 27.01%,32.54%,20.19%,31.15%,and 30.30,respectively.%And 63.16%,the BCF aboveground,BCF underground and transport coefficients of heavy metal Cd in the soil decreased by 24.88%,41.51%,and 22.17%,respectively.（5）Different ratios of humic acid compound attapulgite materials can improve the passivation effect of soil heavy metal Cd and effectively reduce soil environmental risks.Among them,HP15 treatment has the largest change,the passivation effect is the best,and the environmental risk is the smallest.The humic acid compound attapulgite passivation material used in this study has a good passivation effect,in order to provide a reference for the passivation agent to repair heavy metal contaminated soil,and propose an efficient and cheap new method for soil remediation.