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Inorganic electron acceptors coupling of organic matter redox processes contribute to regulate methane emissions in anoxic incubations of different peat soils of China
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  • Zhi-Guo Yu,
  • Xiaoqiao Tang,
  • Hongyan Wang,
  • Amit Kumar,
  • Mengjiao Wang,
  • Giri R. Kattel,
  • Jieyu Yu,
  • Lei Han
Zhi-Guo Yu
Nanjing University of Information Science and Technology

Corresponding Author:[email protected]

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Xiaoqiao Tang
Nanjing University of Information Science and Technology
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Hongyan Wang
Nanjing University of Information Science and Technology
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Amit Kumar
Nanjing University of Information Science and Technology
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Mengjiao Wang
University of Exeter
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Giri R. Kattel
The University of Melbourne
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Jieyu Yu
Nanjing University of Information Science and Technology
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Lei Han
Xi'an Jiaotong-Liverpool University
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Abstract

The availability of electron acceptors (EAs) in peatlands determines the potential of methene (CH 4) formation under anaerobic conditions. Previous studies suggested that EAs can suppress CH 4 production based on Gibbs free energy under the Redox Ladder Theory. However, there is a growing body of evidence that challenges this theory, raising the question of how the coupling of soil substrates with EAs influences CH 4 emissions. To answer this key question, peat soils were collected across different climatic zones with different degrees of soil degradation. Anoxic incubation experiments were set up, and continuous addition of SO 4 2-, Fe 3+ and humic acid (HA) at different levels of concentrations followed by characterization of dissolved organic matter (DOM) using fluorescence spectroscopy. Results suggest that low concentrations of SO 4 2- (1000 μmol L -1), Fe 3+ (100 μmol L -1), and HA (30 mgC L -1) promoted CH 4 production in most of the peat soils. With the addition of SO 4 2- and HA, increased CH 4 emissions were contributed to the facilitation of dissolved organic carbon and reduced quinone-like component C1, which increased the substrate availability for methanogenesis. Furthermore, strengthened microbial activity as indicated by fluorescence component C2 led to higher CH 4 production under Fe 3+ treatments. On the other hand, at high concentrations of SO 4 2- (5000 μmol L -1), Fe 3+ (500 μmol L -1) and HA (50 mgC L -1), CH 4 emissions rapidly decreased by 70.65 ± 1.57% to 96.25 ± 0.45% compared to control group without EAs addition, accompanied by increased δ 13C-CH 4 signatures indicating the outweighed CH 4 production under anaerobic oxidation of methane (AOM) when coupling with reduced EAs. The effect of EAs on CH 4 emissions in peat soils could also be related to natural organic substrates. Our results suggest that the CH 4 production in peatlands could be facilitated by regulating organic substrates at low EAs concentrations, but excessive EAs will reduce net CH 4 emissions through AOM.