Natural Fe-bearing clay mineral enhanced Fe reduction, pollution attenuation and biotic-abiotic linkage in sediments

Fe-bearing clay minerals usually serve as promising tools for bolstering pollutants transformation by co-acting with microbes. However, the underlying interactions between Fe-bearing clay mineral and sediments microbes, and their involvement in pollutants transformation remain largely unknown. Natural Fe-poor Swy-3 and Fe-rich NAu-2 clay minerals were introduced to 2,4-DCP polluted sediments. Fe states evaluation demonstrated that NAu-2 facilitated microbially iron reduction and low-to-high crystalline transformation, driven by Geobacter-dominated Fe(III)-reducing bacteria (FeRB, R² = 0.79), with Fe(III) serving as the terminal electron acceptor. These Geobacter-dominated FeRB synergized with metabolic bacteria to strengthen electron supply and reducing power (ATP, NADP) through up-regulated TCA cycle, glycolysis and pentose phosphate pathway. Integrating Mantel test, we deduced that core-modularized FeRB (Geobacter, Anaeromyxobacter, Bacillus) in microbial network promoted efficient electron transfer between H₂ (electron donors) and 2,4-DCP (electron acceptors), achieving near-complete removal of 2,4-DCP and reducing its natural half-life by ∼10 days. Further, PLS-SEM revealed that 2,4-DCP initially stimulated dehydrogenase activity (0.35*) and dechlorinating bacteria (0.82^**), while NAu-2 exhibited a temporal shift from direct promotion of Fe(II) generation (0.94*) in early stages to indirect regulation through Geobacter-dominant FeRB (1.05^***) in later phases. This study elucidates the complex biotic-abiotic mechanism governing pollution dynamics in Fe-bearing clay mineral-amended sediments.