A novel belowground in-situ gas labeling approach: CH4 oxidation in deep peat using passive diffusion chambers and 13C excess

In-vitro incubation of environmental samples is a common approach to estimate CH4 oxidation potential. Here we developed and verified an in-situ method utilizing passive diffusion chambers (PDC, silicone tubes) to deliver 13C-labeled CH4 into peat for the determination of the CH4 oxidation potential based on 13C excess of CO2. To target CH4 oxidation under semi-aerobic and anaerobic conditions, we installed 20 PDCs (30 ml volume) below the water table in profiles from 35-cm to 2-m depths of a peatland in north-eastern Sweden in July 2017 using a peat auger. 13C-labeled CH4 was injected into PDCs through tubing twice during 12 days (day 0 and 6) and samples were collected at days 1, 3, 6, 8 and 11. Background (non-labeled) δ13C of CO2 ranged from −7.3 (35 cm) to +5.7‰ (200 cm) with depth. These δ13C values rose to +110 and + 204‰ after the CH4 injection. The estimated CH4-derived C in CO2 was the lowest at the bottom of the profile (0.3 μmol L−1), whereas the maximum was at 100 cm (6.1 μmol L−1) at five days after the second labeling. This corresponded to 1.5–7.2% of the total CH4 pool to be oxidized, depending on depth. This novel approach with belowground in-situ 13C labeling of gases demonstrated the suitability of tracing the transformations of these gases in soil depth by PDCs and for the first time verified the in-situ occurrence of a deep-peat CH4 oxidation. © 2021 Elsevier B.V.

Dorodnikov M.1, 2, 5 , Knorr K.-H.3 , Fan L.1 , Kuzyakov Y. 1, 6 , Nilsson M.B.4
Elsevier B.V.
  • 1 Department of Soil Science of Temperate Ecosystems, University of Göttingen, Göttingen, 37077, Germany
  • 2 Department of Biogeochemistry of Agroecosystems, University of Göttingen, Göttingen, 37077, Germany
  • 3 Ecohydrology and Biogeochemistry Group, Institute of Landscape Ecology, University of Münster, Germany
  • 4 Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
  • 5 Tyumen State University, Tyumen, 625003, Russian Federation
  • 6 Agro-Technological Institute, RUDN University, Moscow, 117198, Russian Federation
Ключевые слова
CH4 oxidation; Greenhouse gases; In-situ labeling; Methane; Passive diffusion chamber; Peatland
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