[Remediation of Pb and Cd-contaminated Soil by Biochar-based@ZVI/Chlorapatite Composite Material]

To investigate the immobilization effects of biochar-supported nano zero-valent iron/chlorapatite composite on lead （Pb） and cadmium （Cd） contamination in soil, as well as its influence on plant heavy metal uptake, a series of soil incubation and pot experiments were conducted. The study examined the impact of the composite on soil pH, cation exchange capacity （CEC）, organic matter （OM） content, and the speciation of Pb and Cd in soil. The results demonstrated that the composite significantly increased soil pH, CEC, and OM content while transforming Pb and Cd from acid-extractable and reducible forms to oxidizable and residual forms. The Pb content in the above-ground and root tissues of amaranth plants decreased by 31.94% and 38.34%, respectively, while the Cd content decreased by 63.68% and 49.45%, respectively. Further analysis revealed significant correlations （P<0.05） between the acid-extractable and residual fractions of Pb and Cd in soil and the heavy metal content in amaranth plants. These findings suggest that the biochar-supported zero-valent iron/chlorapatite composite exhibits excellent potential for immobilizing active Pb and Cd in soil, improving soil physicochemical properties, and reducing heavy metal uptake by plants. These composites hold promise for the remediation of Pb and Cd-contaminated soils.