Remediation of Cadmium Pollution in Paddy Soil by FeMg-LDH/bentonite Mixed with Compost and Effect on Soil Microorganisms

Cadmium (Cd) contamination poses a serious issue in paddy soils due to its significant health risks through transport in soil-food chains. Although the stabilization of Cd in soils and its reduction in rice plants have been extensively studied, the effects on soil microorganisms, particularly the comparison of microbial species diversity and composition between contaminated and uncontaminated soils after restoration, remain insufficiently explored. This study aims to develop FeMg-LDH/Bentonite mixed with compost as an effective stabilizer to reduce Cd mobility in paddy soils. Characterization results reveal that FeMg-LDH/Bentonite exhibits a three-dimensional layered petal-like structure. The adsorption mechanisms of FeMg-LDH/Bentonite suggest the presence of surface complexation, ion exchange, and chemical precipitation interactions between FeMg-LDH/Bentonite and heavy metals. Using the community Bureau of Reference (BCR) sequential extraction procedure to evaluate remediation efficiency, FeMg-LDH/Bentonite mixed with compost effectively reduces the bioavailable Cd in soil and the Cd concentration in plants. The introduction of this material leads to changes in several factors, including soil pH, water-soluble organic carbon (WSOC), enzyme activity, soil microbial community abundance, and specific microbial community composition, ultimately influencing the solubility and speciation of Cd. The research findings demonstrate that a composite material composed of FeMg-LDH/Bentonite and compost, in specific proportions, effectively reduces the bioavailability of Cd in soil while also alleviating the adverse effects of Cd contamination on soil microbial communities and enzyme activity. This study provides valuable insights into efficient strategies for controlling Cd bioavailability in Cd-contaminated paddy soils.