Mechanisms and Management Strategies of Microbial Community-Driven Iron-Manganese Biogeochemical Cycling in the Hyporheic Zone: A Case Study of the Liaohe Riverbank Filtration System

Riverbank filtration (RBF) significantly alters the hydrodynamic and redox conditions in the hyporheic zone, thereby influencing the migration and transformation of iron (Fe) and manganese (Mn). This study investigated the Liaohe Riverbank Filtration System by integrating 16S rRNA high-throughput sequencing, hydrogeochemical parameter analysis, and metagenomics to unravel the spatial heterogeneity of microbial communities and their driving mechanisms on Fe/Mn cycling. Key findings include: (1) In the shallow hyporheic zone (0–17 m), Proteobacteria (38.7%) and iron-reducing genera (Geobacter, Pseudomonas) dominated, with their abundance strongly correlated with Fe²⁺ concentration (R²=0.83), indicating dissimilatory iron reduction as the core mechanism for Fe mobilization; (2) In the deep hyporheic zone (17–350 m), sulfate-reducing bacteria (Desulfobacca) and manganese-reducing bacteria (Flavobacterium) mediated Mn²⁺ immobilization via sulfide precipitation (removal efficiency 40–60%); (3) A redox gradient-driven “Three-Zone Microbial Functional Zonation Model” was proposed, delineating the spatial boundaries of O₂/NO₃⁻ reduction, Fe³⁺/Mn⁴⁺ reduction, and SO₄²⁻ reduction zones, with 85% prediction accuracy validated across 12 global RBF sites. Practical engineering strategies, including optimized well placement, sulfate-enhanced bioremediation, and real-time monitoring networks, improved Fe/Mn removal efficiency by 25% and 18%, respectively. This study provides critical insights for water quality risk management and bioremediation in RBF systems.