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| Titel |
Contributions of organic matter and organic sulfur redox processes to electron flow in anoxic incubations of peat |
| VerfasserIn |
Zhiguo Yu, Stefan Peiffer, Jörg Göttlicher, Klaus-Holger Knorr |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110919
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| Publikation (Nr.) |
 EGU/EGU2015-10963.pdf |
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| Zusammenfassung |
| Anaerobic decomposition of peat soils involves a number of interdependent microbial
processes that ultimately generate CO2 and CH4. In many peat soils, a high ratio of CO2:CH4
was reported, which presumably results from a direct or indirect role of soil organic matter
serving as an electron acceptor. Therefore, in this study we intended to test the
hypothesis that organic matter (OM) suppresses methanogenesis and sustains anaerobic
CO2 production, serving as i) direct electron acceptor or ii) via supporting internal
sulfur cycling to maintains CO2 production through bacterial sulfate reduction
(BSR). We incubated peat samples of commercial bog peat, inoculated with a small
amount of fresh peat to introduce an active microbial community. Samples were
amended with sulfate or sulfide and incubated under anoxic conditions for 6 weeks at
30 Ë C. Upon anaerobic incubation of peat virtually devoid of inorganic electron
acceptors, CO2 and CH4 were produced at a ratio of 3.2. According to the electron
budget, the calculated electron accepting capacity (EAC) of OM was 2.36 μeq cm3
d-1. Addition of sulfate significantly increased CO2 production and effectively
suppressed CH4 production. After subtracting the EAC provided though sulfate
addition (0.97~2.81 μeq cm-3 d-1), EACs supplied by OM reached 3.88 to 4.85 μeq
cm-3 d-1.The contribution of organic sulfur was further evaluated by XANES
spectroscopy and using natural abundance of δ34S as a tracer. Results demonstrated
that BSR involved both addition of H2S and sulfate to OM leading to a formation
of reduced organic sulfur and partial changes of oxidized organic sulfur species.
The original peat prior to incubation contained 70.5% reduced organic S (R-S-H,
R-S-R, R-S-S-R), and 25.9% oxidized S (R-SO3, R-SO2-R, R-SO4-R), whereas the
treatment with H2S or sulfate addition comprised 75.7~ 81.1% reduced organic
S, and only 21.1~18.9 % oxidized S. Our results imply that that organic matter
contributes to anaerobic respiration i) directly by electron accepting capacity of redox
active functional groups ii) directly by oxidized organic sulfur and iii) indirectly
by recycling of sulfide to maintain BSR. Moreover, investigating the stability of
organic sulfur compounds in peat soil towards abiotic and biotic reduction and
oxidation is essential for the understanding of environmental sulfur cycling in anaerobic
systems.
Keywords: Methanogenesis; Electron transfer; organic sulfur; Redox processes;
Freshwater systems; |
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