Fe/Mn (Hydr)Oxide-Phosphate Mineral Composites Mitigate Metals Toxicity and Enhance Microbial Community Functionality in Cadmium, Lead, Copper, and Zinc Co-Contaminated Soil

Abstract

Soil heavy metal pollution, particularly multi-metal contamination, poses a critical environmental challenge. Stabilization has emerged as a viable approach to mitigate pollution while preserving soil ecological functions. This work utilized a novel function materials, FMPs, composed of Fe/Mn (hydro)oxides and phosphate minerals, by optimizing the molar ratios of Fe(II), Fe(III), Mn(II), and PO43−. After 60 days of FMPs application (5 wt.%), DTPA-extractable Cd, Pb, Cu, and Zn decreased by 70.10%, 99.82%, 68.30%, and 75.05%, respectively, meeting stabilization criteria (HJ 1282−2023). Notably, FMPs promoted the transformation of Cd, Pb, Cu, and Zn from labile (F1/F2) to stable (F3/F4) fractions. Furthermore, FMPs significantly increased soil pH, EC, TP, AP, and NH4+-N while enhancing S_ACP, S_CL, and S_CAT activities, but reduced Eh, NO3−-N, AK, and S_UE activity. Microbial community analysis revealed that FMPs reshaped soil microbial communities, reducing bacterial diversity and richness (p < 0.05) but increasing fungal diversity and richness (p < 0.05). Molecular ecological networks demonstrated tighter bacterial connections and simplified fungal networks, with low-abundance taxa playing critical ecological roles. Microbial community assembly was dominated by stochastic processes, leading to a stabilized community structure. These findings underscored FMPs as an effective and ecologically sustainable material for multi-metal contaminated soil remediation.

Keywords: heavy metals, Multi-Metal Contaminated Soil, Simultaneous Stabilization, Leaching Toxicity, ecological effects