Abstract：
Microbially induced carbonate precipitation (MICP) is a promising technique for remediating heavy metal-contaminated soils. However, the effectiveness of MICP in immobilizing Cd in alkaline calcareous soils, especially when applied in agricultural soils, remains unclear. Biochar and magnesium oxide are two environmentally friendly passivating materials, and there are few reports on the combined application of MICP with passivating materials for remediating heavy metal-contaminated soils. Additionally, the number of treatments with MICP cement and the concentration of calcium chloride during the MICP process can both affect the effectiveness of heavy metal immobilization by MICP. Therefore, we conducted MICP and MICP-biochar-magnesium oxide treatments on agricultural soils collected from Baiyin, Gansu Province (pH = 8.62), and analyzed the effects of the number of treatments with cement and the concentration of calcium chloride on the immobilization of Cd by MICP and combined treatments. The results showed that early-stage MICP could immobilize exchangeable cadmium and increase the residual cadmium content, especially with high-concentration calcium chloride MICP treatment. However, in the later stage, soil nitrification and exchange processes led to the dissolution of carbonate-bound cadmium and cadmium activation. The fixing effect of MICP influence whether the MICP-MgO-biochar is superior to the MgO-biochar. Four treatments with cement were more effective than single treatment in MICP-biochar-magnesium oxide treatment, and the MICP-biochar-magnesium oxide treatment with four treatments was the most effective, with passivation rates of 40.7% and 46.6% for exchangeable cadmium and bioavailable cadmium, respectively. However, attention should be paid to the increase in soil salinity. The main mechanism of MICP-magnesium oxide-biochar treatment in immobilizing cadmium was the formation of Cd(OH)2, followed by the formation of cadmium carbonate.
摘要：
微生物诱导碳酸盐沉淀（MICP）是修复重金属污染土壤的一种有前途的技术。然而,MICP在碱性钙质土壤中固定Cd的有效性，特别是当应用于农业土壤时，尚不清楚。生物炭和氧化镁是两种环保钝化材料，关于MICP与钝化材料联合应用修复重金属污染土壤的报道很少。此外,在MICP过程中，MICP水泥的处理次数和氯化钙的浓度都会影响MICP固定重金属的有效性。因此,我们对从白银收集的农业土壤进行了MICP和MICP-生物炭-氧化镁处理，甘肃省(pH=8.62),并分析了水泥处理次数和氯化钙浓度对MICP和联合处理固定Cd的影响。结果表明，早期MICP可以固定交换性镉，增加残留镉含量，特别是用高浓度氯化钙MICP处理。然而,在后期,土壤硝化和交换过程导致碳酸盐结合的镉和镉活化的溶解。MICP的固定效果影响MICP-MgO-生物炭是否优于MgO-生物炭。在MICP-生物炭-氧化镁处理中，四种水泥处理比单一处理更有效。MICP-生物炭-氧化镁处理四种处理是最有效的，可交换镉和生物可利用镉的钝化率为40.7%和46.6%，分别。然而,应注意土壤盐分的增加。MICP-氧化镁-生物炭处理固定镉的主要机理是形成Cd（OH）2，其次是形成碳酸镉。
