Efficient remediation of Hg in soils by iron-based materials: Environmental variable effect and regulatory mechanisms

The effectiveness of iron-based materials in soil remediation has gained significant attention. The mechanisms underlying the methylation and demethylation of mercury (Hg) by iron materials were still elusive. In this study, the effect of typical iron materials (pyrrhotite, hematite, and zero-valent iron (ZVI)) on the transformation of Hg were investigated. The supplementation of various iron-based material increased the THg removal efficiency in soil, particularly with ZVI, which was 5.6-14.2 % higher than that of the control. The iron-based materials also reduced the stress of Hg on plants and soil by decreasing the transformation and translocation of Hg and increasing oxidative enzyme activity of plants. The ZVI decreased the MeHg content in plants (0.1 mg/kg) compared to the control group (0.3 mg/kg). The relative abundances of genes that encoded Hg transportation (e.g. merA), glycolysis, TCA, and iron reduction were increased with the addition of iron materials. Iron-based materials also increased the complexity of the bacterial network, thereby enhancing the robustness of the microbial environmental systems that against Hg stress. The present study provided a comprehensive assessment of the efficacy of iron-based materials in remediating Hg-contaminated soils.