Dose relationships and interactions of four materials and MICP technology in simultaneously reducing the exchangeable parts of As, Pb, and Cd in multiple contaminated soils

Purpose The combined contamination of As, Pb, and Cd in soil has caused serious environmental problems. In order to find a more suitable remediation method, this study used the combination of amendment materials and microorganisms to synchronously stabilize As, Pb, and Cd in compound contaminated soil. Materials and methods The metallogenic characteristics of Lysinibacillus fusiformis were verified by SEM, XRD, FTIR, and other characterization methods; four kinds of amendment materials and microbial agent were used to carry out the comparative experiments of unitary and binary remediation respectively to stabilization soil potentially toxic element(s) (PTEs). By changing the addition amount of materials, the effects on soil physical and chemical properties, speciation transformation, and content of As, Pb, and Cd were discussed. Results The results of comparative experiments show that the stabilization effects of loess combined with microbial agent on As and Pb are significantly improved, reaching 43.86% and 83.52%, respectively. The combination of compost sludge and microbial agent can effectively improve the stabilization effect of As, reaching 44.53%. Compost sludge can effectively reduce the content of exchangeable fraction of Pb whether used alone or combined with microorganisms. In the experiments of different addition amounts, there was no significant relationship between the addition amount and the stabilization efficiency of three PTEs when loess was added alone, but after combined with microbial agent, the stabilization efficiency of As, Pb, and Cd increased with the increase of the addition amount of loess. Conclusions The combination of loess and MICP may be an effective method to synchronously stabilize As, Pb, and Cd in soil. Loess, attapulgite clay 1, and attapulgite clay 2 are suitable for As stabilization. Compost sludge and attapulgite clay 1 are more favorable for Pb stabilization. Loess, compost sludge, and attapulgite clay 1 promote Cd stabilization effect. Loess and compost sludge are more suitable for combination with microorganisms.