Simultaneous stabilization of high-concentration multi-heavy metal(loid)s co-contaminated soil using Fe/Mn (hydr)oxide-humic acid composites:A novel approach towards sustainable environmental remediation.

In this work, a green and highly efficient functional material (FMHs) was developed through the precise optimization of Fe2+, Fe3+, Mn2+, and humic acid (HA) ratios. The stabilization efficacy of FMHs on the high-concentration Cd-Pb-Cu-Zn-As-Sb co-contaminated soil and its potential ecological impacts were comprehensively evaluated from multiple perspectives. After 60 days of soil remediation with 5 wt% FMHs, the extractable Cd, Pb, Cu, Zn, As, and Sb were reduced by 59.06 %, 99.83 %, 92.60 %, 92.43 %, 98.06 %, and 77.04 %, respectively. These reductions were primarily attributed to the FMHs-driven transformation of unstable or substable metal(loid) species into stable residual forms. Furthermore, FMHs application enhanced soil redox potential (Eh), electrical conductivity (EC), nitrogen content (TN, NH4+-N, NO3--N), and enzymatic activities (acid phosphatase, sucrase, cellulase, and catalase), while concurrently reducing soil pH, phosphorus, potassium content, and urease activity. Molecular ecological network analyses revealed that FMHs significantly reshaped soil bacterial diversity and microbial community structure, reducing the complexity of bacterial and fungal networks while fostering positive correlations. Bacterial community assembly was predominantly governed by stochastic processes, with environmental variables playing a pivotal role in shaping the assembly dynamics. In summary, this work provided new insights and technologies for the personalized design and fabrication of functional materials for the simultaneous stabilization and remediation of multi-metal(loid)s contaminated soils.