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Valenzuela, Edgardo I. ; Bryce, Casey ; Forberg, Judith ; Planer-Friedrich, Britta ; Kappler, Andreas ; Cervantes, Francisco J.:
Unraveling the role of sulfide-natural organic matter interplay on methane cycling in anoxic environments.
In: Biogeochemistry.
Bd. 161
(2022)
Heft 2
.
- S. 193-206.
ISSN 1573-515X
DOI: https://doi.org/10.1007/s10533-022-00977-x
Abstract
Redox-active natural organic matter (NOM) possesses great potential to fuel chemical and biological reactions due to its electron-transferring capacity. Chemical sulfide oxidation with redox-active NOM as the terminal electron acceptor (TEA) has been shown to determine the extent to which organic matter degradation produces CO2 or CH4 by suppressing methanogenesis. However, the effect that such S cycling reactions potentially have on CH4-consuming processes, such as sulfate- and NOM-dependent anaerobic oxidation of methane (AOM), is yet to be disclosed. In this study, bulk Pahokee Peat humic substances (PPHS) were employed as a model source of redox-active NOM to test their role as TEA for the chemical oxidation of dissolved sulfide. While elemental sulfur was the dominant product of sulfide oxidation (~ 50 to 75% of oxidized sulfur), thiosulfate was the second most abundant product accounting for ~ 20% of the oxidized sulfide. The incorporation of S into PPHS’ organic structure was revealed by the formation of methylthio, ethylthio, thiol, and aromatic-disulfide/polysulfide moieties after the reaction, which may compromise the availability of NOM to act as TEA for the oxidation of organic matter or methane. Wetland sediment incubations amended with sulfate and PPHS revealed that PPHS were the preferential TEA for catalyzing AOM (NOM-AOM) while sulfate suppressed methanogenic activities. Considering this and several novel findings concerning sulfate- and NOM-driven AOM, we discuss novel mechanisms by which sulfur/organic matter interactions could impact the microbial processes of CH4 production and consumption.