Remediation of cadmium-contaminated soil with iron-modified montmorillonite: Insight for cadmium bioavailability and rhizosphere soil bacterial community

Cadmium (Cd) contamination in agricultural soils poses serious environmental and food safety risks. This study evaluated the remediation potential of iron-modified montmorillonite (GMt) for Cd contamination in rhizosphere soils through pot experiments using perennial ryegrass ( Lolium perenne L.). The results showed that the application of GMt improved the physical and chemical properties of the soil (pH, total nitrogen, available nitrogen, and available potassium). GMt significantly reduced Cd bioavailability by 53.48 %-87.04 % (p < 0.05), accompanied by a decrease in acid-soluble and reducible Cd fractions and an increase in oxidizable and residual fractions. GMt also enhanced soil urease and catalase activity (p < 0.05), optimized rhizosphere bacterial community structure, particularly enriching genera associated with nutrient cycling and heavy metal tolerance. GMt reduced Cd accumulation in ryegrass by 23.54 %-27.03 %, lowering the risk of Cd entering the food chain. These findings highlight that GMt is a promising amendment for immobilizing Cd and has broad application prospects in improving soil health and ensuring food security. • GMt enhances soil properties, which contributes to improved soil quality. • GMt converts more acid-soluble Cd into less accessible forms. • GMt obviously reduces the soil Cd bioavailability and reduced the risk to plants. • GMt shifts the rhizosphere bacteria community and thus promotes Cd passivation.