Liu Jiarui, Klonicki-Ference Emily, Krause Sebastian J E, Treude Tina
Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California 90095, United States.
Earth Research Institute, University of California, Santa Barbara, California 93106, United States.
Environ Sci Technol. 2025 Jan 14;59(1):513-522. doi: 10.1021/acs.est.4c10639. Epub 2024 Dec 31.
Wetland methane emissions are the primary natural contributor to the global methane budget, accounting for approximately one-third of total emissions from natural and anthropogenic sources. Anaerobic oxidation of methane (AOM) serves as the major sink of methane in anoxic wetland sediments, where electron acceptors are present, thereby effectively mitigating its emissions. Nevertheless, environmental controls on electron acceptors, in particular, the ubiquitous iron oxides, involved in AOM are poorly understood. Here, we explored methane sinks within a hypersaline pool situated in a coastal wetland. The geochemical profiles reveal a tiering, where microbial sulfate reduction dominates in the organic-rich surface sediment, yielding to iron reduction in the deeper organic-poor yet sulfate-rich subsurface sediment. This shift is attributed to the drilling-induced depression and subsequent diagenetic transformation of the surface sediment. Radiotracer incubations demonstrate a strong association of AOM with sulfate in surface sediment and with iron oxides in subsurface sediment. Despite high concentrations of sulfate in coastal wetlands, Fe-dependent AOM may play a significant, yet often under-considered, role as a sink for methane emissions.
湿地甲烷排放是全球甲烷收支的主要自然贡献源，约占自然和人为源总排放量的三分之一。甲烷厌氧氧化（AOM）是缺氧湿地沉积物中甲烷的主要汇，在该沉积物中存在电子受体，从而有效减少甲烷排放。然而，人们对参与AOM的电子受体，特别是普遍存在的铁氧化物的环境控制了解甚少。在此，我们探索了位于沿海湿地的一个高盐池中甲烷的汇。地球化学剖面显示出一种分层现象，其中在富含有机物的表层沉积物中微生物硫酸盐还原占主导，而在更深层的贫有机但富含硫酸盐的次表层沉积物中则转变为铁还原。这种转变归因于钻孔导致的表层沉积物凹陷以及随后的成岩转变。放射性示踪剂培养表明，AOM在表层沉积物中与硫酸盐密切相关，在次表层沉积物中与铁氧化物密切相关。尽管沿海湿地中硫酸盐浓度很高，但依赖铁的AOM可能作为甲烷排放的汇发挥着重要但常被忽视的作用。
