【标题】Humic acid-mediated activation of antimony colloid during soil redox cycles: Mechanisms and environmental implications

【期刊】Journal of Hazardous Materials

【第一作者】郑雄开

【摘要】Soil redox fluctuation is a primary driver of antimony (Sb) mobilization in contaminated soils. However, the regulatory effects and mechanisms of exogenous humic acid (HA) on Sb colloids (1–450 nm) under dynamic redox conditions remain unclear. In this study, five consecutive aerobic–anaerobic incubations were performed on three Sb-contaminated soils with a contamination gradient (S1 > S2 > S3). Combining particle-size fractionation, sequential extraction, XPS, TEM-EDS, Spearman-Mantel analysis and PLS-PM, we explored the impacts of HA (10 mg C L−1) on Sb release, speciation transformation, colloid distribution and underlying mechanisms. The results showed that HA significantly promoted total dissolved Sb (< 450 nm) release by up to 122.5% relative to the control. More importantly, HA-induced Sb activation involved both total < 450 nm Sb mobilization and size redistribution from large colloids (220–450 nm) toward small colloids (1∼3–220 nm), which maintained 20%–60% of total Sb as fine colloidal species. Under anaerobic conditions, HA facilitated Sb(V) reduction to Sb(III), increasing Sb(III) proportion by 30%–50%. HA also stabilized Sb in the reducible Fe oxide-bound fraction and decreased ion-exchangeable and adsorbed Sb. Correlation and quantitative modeling verified Fe oxides as the core inorganic carrier of Sb colloids, and HA shifted Sb colloid regulation from inorganic dominance to inorganic–organic synergistic control driven by Fe colloids and HA-derived DOM. This study clarifies HA’s multifunctional regulation on Sb colloids under redox cycles and identifies colloidal Sb as the dominant mobile Sb form, providing a theoretical basis for risk assessment and in-situ remediation of Sb-contaminated soils in wet-dry alternating environments.

【文章链接】https://doi.org/10.1016/j.jhazmat.2026.142696