Microbial Carbonate Biomineralization in Soil Systems: Coupling Carbon Locking, Heavy-Metal Immobilization, and Soil Restoration

Heavy-metal contamination and uncertainty regarding the long-term stability of soil carbon represent interconnected challenges for sustainable soil management. Although carbon sequestration and heavy-metal remediation have been widely investigated, their functions are generally considered separately, highlighting the need for integrated approaches. This review examines biogenic mineralization as a potential pathway for coupling mineral carbon stabilization with heavy-metal immobilization in contaminated soils, with particular emphasis on microbially induced carbonate precipitation (MICP). The review synthesizes the microbial and geochemical mechanisms governing carbonate formation through ureolysis, carbonic anhydrase activity, the oxalate–carbonate pathway, denitrification, and sulfate reduction and evaluates the interactions of resulting carbonate minerals with heavy metals through adsorption, co-precipitation, surface complexation, and lattice incorporation. Particular attention is given to carbonate mineral stability, metal-specific behaviour, life-cycle carbon requirements, non-target soil and plant effects, and evidence from laboratory, mesocosm, and field-scale studies. The synthesis indicates that biogenic carbonate formation offers a conceptual framework for linking mineral carbon stabilization with heavy-metal immobilization; the two functions are supported by largely separate bodies of evidence that have not yet been jointly demonstrated in the same system, and the magnitude and persistence of either benefit depend on microbial pathway, soil properties, contaminant chemistry, mineral phase, and environmental conditions. Ureolysis-driven MICP remains the most extensively investigated pathway; however, its remediation efficiency does not necessarily indicate a net climate benefit because reagent production, microbial cultivation, ammonium management, and carbonate dissolution can substantially affect the overall carbon balance. Furthermore, carbonate precipitation may immobilize cationic metals while potentially increasing the mobility of oxyanionic contaminants such as As and Cr under alkaline conditions. Overall, biogenic mineralization represents a promising but context-dependent strategy. Full life-cycle carbon accounting, mechanism-specific validation, assessment of non-target effects and remobilization, and long-term field trials are needed to establish its durability and practical environmental benefits.