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Abstract Most peat domes in Southeast Asia are crisscrossed by networks of drainage canals. These canals are a potentially important source of methane to the atmosphere because the groundwater that discharges into them carries high concentrations of dissolved methane that is produced within peat. In this study, we present an isotope‐enabled numerical model that simulates transport, degassing, and oxidation of methane and dissolved inorganic carbon (DIC) along a drainage canal. We then estimate methane fluxes through a 5‐km canal that crosses a disturbed, forested, but undeveloped, peat dome in Brunei Darussalam by applying this model to field data: concentrations and stable carbon isotopic ratios of both methane and dissolved inorganic carbon from both peat porewater and canal water. We estimate that approximately 70% of the methane entering the canal is oxidized within the canal, 26% is degassed to the atmosphere, and 4% is transported toward the ocean, under low to moderate flow conditions. The flux of methane to the atmosphere is lowest at the maximum elevation of the canal, where flow is stagnant and methane concentrations are highest. Downstream, as flow velocity increases, methane emissions plateau even as methane concentrations decrease. The resulting methane emissions from the canal are large compared to emissions from the peat surface and vegetation on a per‐area basis. However, since the canal covers only a small portion of the catchment area, the canal may be a substantial but not dominant source of methane from the peatland.
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Fate of methane in canals draining tropical peatlands
Abstract Tropical wetlands and freshwaters are major contributors to the growing atmospheric methane (CH4) burden. Extensive peatland drainage has lowered CH4emissions from peat soils in Southeast Asia, but the canals draining these peatlands may be hotspots of CH4emissions. Alternatively, CH4oxidation (consumption) by methanotrophic microorganisms may attenuate emissions. Here, we used laboratory experiments and a synoptic survey of the isotopic composition of CH4in 34 canals across West Kalimantan, Indonesia to quantify the proportion of CH4that is consumed and therefore not emitted to the atmosphere. We find that CH4oxidation mitigates 76.4 ± 12.0% of potential canal emissions, reducing emissions by ~70 mg CH4m−2d−1. Methane consumption also significantly impacts the stable isotopic fingerprint of canal CH4emissions. As canals drain over 65% of peatlands in Southeast Asia, our results suggest that CH4oxidation significantly influences landscape-scale CH4emissions from these ecosystems.
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- Award ID(s):
- 2305578
- PAR ID:
- 10554571
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 15
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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