Preprints
https://doi.org/10.5194/bg-2021-13
https://doi.org/10.5194/bg-2021-13

  04 Feb 2021

04 Feb 2021

Review status: this preprint is currently under review for the journal BG.

CO2 emissions from peat-draining rivers regulated by water pH

Alexandra Klemme1, Tim Rixen2,3, Denise Müller-Dum1, Moritz Müller4, Justus Notholt1, and Thorsten Warneke1 Alexandra Klemme et al.
  • 1Institute of Environmental Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
  • 2Leibniz Center for Tropical Marine Research, Fahrenheitstr. 6, 28359 Bremen, Germany
  • 3Institute of Geology, University of Hamburg, Bundesstr. 55, 20146 Hamburg, Germany
  • 4Faculty of Engineering, Computing, and Science, Swinburne University of Technology Sarawak Campus, Jalan Simpang Tiga, 93350 Kuching, Sarawak, Malaysia

Abstract. Southeast Asian peatlands represent a globally significant carbon store that is destabilized by deforestation and the transformation into plantations, causing high carbon dioxide (CO2) emissions from peat soils and increased leaching rates of peat carbon into rivers. While global model studies assumed that CO2 emissions from peat-draining rivers would be high, estimates based on field data suggest they are only moderate. In this study we offer an explanation for this phenomenon and show that carbon decomposition is hampered by the low pH in peat-draining rivers, which limits CO2 production in and emissions from these rivers. We find an exponential pH limitation that shows good agreement with laboratory measurements from high latitude peat soils. Additionally, our results suggest that enhanced input of carbonate minerals increase CO2 emissions from peat-draining rivers by counteracting the pH limitation. As such inputs of carbonate minerals occur due to human activities like deforestation of river catchments, liming in plantations and enhanced weathering projects, our study points out an important feedback mechanism of those practices.

Alexandra Klemme et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-13', Anonymous Referee #1, 22 Feb 2021
    • AC1: 'Reply on RC1', Alexandra Klemme, 09 Jun 2021
  • RC2: 'Comment on bg-2021-13', Anonymous Referee #2, 23 Apr 2021
    • AC2: 'Reply on RC2', Alexandra Klemme, 09 Jun 2021

Alexandra Klemme et al.

Alexandra Klemme et al.

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Short summary
Tropical peat-draining rivers are a natural hotspot for carbon dioxide (CO2) emissions. Measurement-based studies state lower emissions than model-based estimates suggested. We compiled data from ten Southeast Asian rivers and found that CO2 production within these rivers is hampered by low water pH, providing a natural threshold for CO2 emissions. Furthermore, enhanced carbonate inputs, e.g. caused by human activities, suspend this natural threshold and cause increased CO2 emissions.
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