Advances in the remediation of contaminated soils using combined biochar and microorganisms

Heavy metal pollution represents a critical global environmental challenge. Biochar-microbe synergistic remediation (BMS) has emerged as a promising green strategy, enabling simultaneous removal and stabilization of multiple heavy metals through synergistic biochar-microorganism interactions. Experimental results demonstrate its high remediation efficiency: Cr(VI)-reducing bacteria immobilized on Enteromorpha-derived biochar achieved 94.2% conversion of Cr(VI) with approximately 84% total chromium fixation; Pseudomonas-loaded biochar enhanced plant cadmium accumulation by 1.8–2.4 times; and immobilized bacterial communities removed approximately 65% of arsenic via biotransformation and surface co-precipitation. This review systematically elucidates the underlying synergistic mechanisms of BMS, including soil condition improvement, microbial habitat provision, adsorption gradient enhancement, and enzyme activity elevation, while also highlighting its impacts on heavy metal speciation and plant growth. Finally, key future research directions are outlined.