Influence of pH on the balance between methanogenesis and iron reduction
Influence of pH on the balance between methanogenesis and iron reduction
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DOI：
10.1111/gbi.12320
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发表时间：
2018-11
期刊：
影响因子：
3.7
通讯作者：
K. A. Marquart;Ben R. Haller;Janet M. Paper;T. Flynn;M. Boyanov;Ganiyat Shodunke;Colleen M. Gura;Q. Jin;M. Kirk
中科院分区：
文献类型：
--
作者：
K. A. Marquart;Ben R. Haller;Janet M. Paper;T. Flynn;M. Boyanov;Ganiyat Shodunke;Colleen M. Gura;Q. Jin;M. Kirk
甲烷生成和铁还原在确定全球温室气体通量方面起主要作用。尽管它们很重要，但影响它们相互作用的环境因素却鲜为人知。在这里，我们提出的证据表明，pH值显著影响每个反应之间的平衡，在缺氧环境中，含有氧化铁（氧）矿物。在含针铁矿作为铁铁来源的沉积物生物反应器中，铁还原和甲烷生成都发生了，但两者之间的平衡随着pH的变化而显著变化。与接受酸性介质（pH 6）的生物反应器相比，接受碱性介质（pH 7.5）的生物反应器中，电子供体氧化对铁还原的影响降低了85%，对甲烷生成的影响提高了61%。因此，在碱性条件下，产甲烷作用取代了大量的铁还原。从美国含水层收集的地球化学数据表明，在自然环境中，类似的模式也存在于广泛的空间尺度上。相比之下，在没有添加针铁矿的生物反应器中，黏土矿物是铁的来源，每种反应之间的平衡不随pH值的变化而显著变化。因此，我们认为pH值可以调节微生物铁还原和甲烷生成对陆地环境碳通量的相对贡献。我们进一步提出，铁（氧）氧化物矿物的可用性影响了各反应之间的平衡对pH的敏感程度。本研究结果促进了我们对微生物甲烷生成的环境控制的认识，并为利用pH和铁矿物的存在来改进温室气体通量的预测提供了基础。
Methanogenesis and iron reduction play major roles in determining global fluxes of greenhouse gases. Despite their importance, environmental factors that influence their interactions are poorly known. Here, we present evidence that pH significantly influences the balance between each reaction in anoxic environments that contain ferric (oxyhydr)oxide minerals. In sediment bioreactors that contained goethite as a source of ferric iron, both iron reduction and methanogenesis occurred but the balance between them varied significantly with pH. Compared to bioreactors receiving acidic media (pH 6), electron donor oxidation was 85% lower for iron reduction and 61% higher for methanogenesis in bioreactors receiving alkaline media (pH 7.5). Thus, methanogenesis displaced iron reduction considerably at alkaline pH. Geochemistry data collected from U.S. aquifers demonstrate that a similar pattern also exists on a broad spatial scale in natural settings. In contrast, in bioreactors that were not augmented with goethite, clay minerals served as the source of ferric iron and the balance between each reaction did not vary significantly with pH. We therefore conclude that pH can regulate the relative contributions of microbial iron reduction and methanogenesis to carbon fluxes from terrestrial environments. We further propose that the availability of ferric (oxyhydr)oxide minerals influences the extent to which the balance between each reaction is sensitive to pH. The results of this study advance our understanding of environmental controls on microbial methane generation and provide a basis for using pH and the occurrence of ferric minerals to refine predictions of greenhouse gas fluxes.