19 May 2022
19 May 2022
Status: this preprint is open for discussion.

Potential bioavailability of pyrogenic organic matter resembles natural dissolved organic matter pools

Emily B. Graham1,2,, Hyun-Seob Song3,, Samantha Grieger1,4, Vanessa Garayburu-Caruso1,5, James Stegen1, Kevin D. Bladon6, and Allison Myers-Pigg1,4 Emily B. Graham et al.
  • 1Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
  • 2School of Biological Sciences, Washington State University, Richland, WA USA
  • 3Department of Biological Systems Engineering, Department of Food Science and Technology, Nebraska Food for Health Center, University of Nebraska, Lincoln, NE, USA
  • 4Marine and Coastal Research Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA
  • 5School of the Environment, Washington State University, Richland, WA USA
  • 6Department of Forest Engineering, Resources, and Management, Oregon State University, Corvallis, OR, USA
  • These authors contributed equally to this work.

Abstract. Pyrogenic materials generated by wildfires are negatively impacting many aquatic ecosystems. At least ~10 % of dissolved organic matter (DOM) pools may be comprised of pyrogenic organic matter (PyOM) that is generally considered to be more refractory than DOM from other sources. However, there has been no systematic evaluation of bioavailability across a full spectrum of PyOM chemistries. We assessed the potential bioavailability of PyOM in relation to measured and globally ubiquitous DOM compounds using a substrate-explicit model to predict the energy content, metabolic efficiency, and aerobic decomposition of representative PyOM compounds. Overall, we found similar potential bioavailability between PyOM and sediment and surface water DOM. Predicted thermodynamics and carbon use efficiencies of PyOM and DOM were statistically indistinguishable. Within PyOM, phenols and black carbon (BC, defined by Wagner et al. (2017)) had lower metabolic efficiency than other PyOM and DOM compounds, and oxygen limitation had less impact on BC metabolism than on other PyOM classes. Our work supports the recent paradigm shift where PyOM bioavailability may be more comparable to natural organic matter than previously thought, highlighting its potential role in global C emissions and providing a basis for targeted laboratory investigations into the bioavailability of various PyOM chemistries.

Emily B. Graham et al.

Status: open (until 15 Jul 2022)

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Emily B. Graham et al.

Emily B. Graham et al.


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Short summary
Intensifying wildfires are increasing pyrogenic organic matter (PyOM) production and its impact on water quality. Recent work indicates that PyOM may have greater impact on aquatic biogeochemistry than previously assumed, driven by higher bioavailability. We provide a full assessment of the potential bioavailability of PyOM across its chemical spectrum. We indicate that PyOM can be actively transformed within the river corridor, and therefore, may be a growing source of riverine C emissions.