Fe-modified clay minerals enhances iron oxide transformation and microbial ecological succession for simultaneous stabilization of As, Pb, and Cd in smelting soils.

The co-occurrence of arsenic (As), lead (Pb), and cadmium (Cd) in smelting soils presents major challenges due to their contrasting geochemical behaviors. This study investigates the efficacy of Fe-modified clay minerals (ATP@MG) in simultaneous stabilization of As, Pb, and Cd co-contaminated soil, and revealed the impact on soil bacterial community succession. The results showed that ATP@MG amendment substantially altered soil iron speciation, particularly increasing amorphous (Fe0) by 3.04-fold at a 5% dosage. The TCLP extractable of As, Pb, and Cd decreased by 83.46%, 75.02%, and 18.40%, respectively, accompanied by marked increases in their residual fractions (84%, 84% and 69%), compared with the control. Simulated acid-rain leaching confirmed that ATP@MG strengthened Fe-metal(loid) associations and significantly reduced long-term leaching risks. Multi-mechanistic immobilization involved electrostatic attraction, complexation (C=O, -OH and Fe-O), Fe(II)/Fe(III)-mediated redox and physical encapsulation within soil aggregates. ATP@MG also enhanced microbial metabolic activity and reshaped bacterial community composition. ATP@MG selective specific functional bacterial (e.g. Proteobacteria (55.81%), Chloroflexi (13.19%)), followed by ecological succession toward a more stable community structure. Redundancy analysis and PLS-PM indicated that ATP@MG-induced changes in soil pH, EC, Fe0, and Fed were the dominant drivers shaping microbial composition and reducing metal(loid)s bioavailability. Besides, ATP@MG reduced network complexity to enhanced cooperative interactions, and toward ecological recovery to improve the nutrient cycling capacity. Overall, Fe-modified clay minerals demonstrated strong potential for simultaneous stabilization of As, Pb and Cd, while promoting microecological recovery in co-contaminated soils.