Dalian University of Technology School of Environmental Science and Technology, No.2 Linggong Road, Ganjingzi District. Dalian, Liaoning 116024, China; State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
Dalian University of Technology School of Environmental Science and Technology, No.2 Linggong Road, Ganjingzi District. Dalian, Liaoning 116024, China.
Water Res. 2022 Jun 30;218:118501. doi: 10.1016/j.watres.2022.118501. Epub 2022 Apr 25.
Reducing methane emission is of great importance to control the global greenhouse effect. Dissimilatory iron reduction (DIR) coupling of organic matter decomposition may suppress methane production via reducing primary electron donors available for methanogenesis. However, during DIR, the amorphous iron oxides (e.g., ferrihydrite) are easy to transform into more stable crystalline iron minerals, which slowdowns the rate of DIR. Humic substance (HS) with redox activity has been extensively reported to facilitate DIR via "electron shuttles" mechanism, yet little known about the effect of HS on mediating the mineralization of iron oxides and the subsequent influences on DIR and methanogenesis. To clarify this, ferrihydrite and fulvic acid (FA) (as the model substance of HS) were supplied to anaerobic methanogenesis systems. Results showed that FA could significantly decrease the formation of crystalline iron oxides, enhance DIR rate by 13.72% and suppress methanogenesis by 25.13% compared to ferrihydrite supplemented only. By X-ray absorption spectra analysis, it was found that FA could complex with ferrihydrite via forming a Fe-C/O structure on the second shell of Fe atom. Quantum chemical calculation further confirmed that FA reduced the adsorption energy between Fe(II) and ferrihydrite. Our study suggested that rational use of HS to mediate mineralization pathway of iron oxides could efficiently improve the availability of iron oxides to drive DIR and control the conversion of organics into CH in natural or engineered systems.
减少甲烷排放对于控制全球温室效应至关重要。有机物分解的异化铁还原（DIR）偶联可能通过减少用于甲烷生成的主要电子供体来抑制甲烷生成。然而，在 DIR 过程中，无定形氧化铁（例如，水铁矿）很容易转化为更稳定的结晶铁矿物，从而减缓 DIR 的速率。具有氧化还原活性的腐殖质（HS）已被广泛报道可通过“电子穿梭”机制促进 DIR，但对于 HS 介导氧化铁矿化及其对 DIR 和甲烷生成的后续影响知之甚少。为了阐明这一点，将水铁矿和富里酸（FA）（作为 HS 的模型物质）供应给厌氧甲烷生成系统。结果表明，与仅补充水铁矿相比，FA 可显著降低结晶氧化铁的形成，将 DIR 速率提高 13.72%，并将甲烷生成抑制 25.13%。通过 X 射线吸收光谱分析，发现 FA 可以通过在 Fe 原子的第二壳层上形成 Fe-C/O 结构与水铁矿络合。量子化学计算进一步证实，FA 降低了 Fe(II)与水铁矿之间的吸附能。我们的研究表明，合理利用 HS 来调节氧化铁的矿化途径可以有效地提高氧化铁的可用性，以驱动 DIR，并控制有机物在自然或工程系统中转化为 CH。
