Elucidating Microbial Mechanisms of Biochar-Enhanced Microbially Induced Carbonate Precipitation at the Molecular Level

This study identifies critical dosage thresholds in biochar-enhanced microbially induced carbonate precipitation (BC-MICP) systems for effective cadmium (Cd) remediation in both aquatic and soil environments. In water, 250 mg/L BC optimized Cd fixation (61.4%) via synergistic adsorption-precipitation effects, regulated by urease activity thresholds (0.4 μg/mL). In soil, addition of >2.5% BC activated heterogeneous CdCO3 nucleation, increasing residual Cd by 19.9%. BC-mediated microbial shifts revealed low-dose enrichment of Cd-resistant Bacillus contrasted with high-dose dominance of oligotrophic Actinobacteria. Fluorescence spectroscopy demonstrated matrix-specific organic interactions: humic acid stabilization in water as opposed to protein-BC binding in soil. Our findings highlight BC’s dual role in bridging adsorption kinetics and microbial metabolism, providing critical thresholds for eco-engineered remediation.