LEACHING CHARACTERISTICS OF MICP SOLIDIFIED LEAD-CONTAMINATED SOIL UNDER ACID RAIN LEACHING CONDITIONS

Acid rain can react with carbonate formed in the process of MICP mineralization,destroy the structural strength of materials and release the fixed heavy metal ions again.However,the research on this technology in acid rain condition is less,and the acid corrosion resistance is not clear.Therefore,it is of practical significance to study the leaching characteristics of MICP solidified heavy metal contaminated soil under acid rain infiltration.In this paper,three typical acid rain conditions with a pH of 3.5,4.5 and 5.6 were designed.Deionized water with a pH of 7.5 was used as a control.The experimental study on MICP solidified lead-contaminated soil was carried out by using soil column leaching method.The influence of pH value of acid rain on strength,pH value,leaching amount of Pb²⁺,Ca²⁺ and occurrence form of Pb²⁺ was analyzed.The results show that: as the pH value of acid solution decreases,the strength of MICP solidified sample decreases,But as the pH value of leaching solution decreases,the leaching amount of Pb²⁺ and Ca²⁺ increases,When the exchangeable Pb²⁺ in solidified sample increases,and the Pb²⁺ in carbonate bound,iron manganese oxide bound,organic matter bound and residue state would decrease.The sample would be less affected by acid rain of 5.6 pH,while the pH value is 3.5,the sample change significantly.