Potential bioavailability of representative pyrogenic organic matter compounds in comparison to natural dissolved organic matter pools

Authors

Emily B. Graham, Pacific Northwest National Laboratory, Washington State University
Hyun-Seob Song, University of Nebraska - LincolnFollow
Samantha Grieger, Pacific Northwest National Laboratory
Vanessa A. Garayburu-Caruso, Pacific Northwest National Laboratory, Washington State University
James C. Stegen, Pacific Northwest National Laboratory, Washington State University
Kevin D. Bladon, Oregon State University
Allison N. Myers-Pigg, Pacific Northwest National Laboratory, Washington State University, University of Toledo

Date of this Version

4-13-2023

Citation

Biogeosciences, 20, 3449–3457, 2023 https://doi.org/10.5194/bg-20-3449-2023

Comments

Used by permission.

Abstract

Pyrogenic organic matter (PyOM) from wildfires impacts river corridors globally and is widely regarded as resistant to biological degradation. Though recent work suggests PyOM may be more bioavailable than historically perceived, estimating bioavailability across its chemical spectrum remains elusive. To address this knowledge gap, we assessed potential bioavailability of representative PyOM compounds relative to ubiquitous dissolved organic matter (DOM) with a substrate-explicit model. The range of potential bioavailability of PyOM was greater than natural DOM; however, the predicted thermodynamics, metabolic rates, and carbon use efficiencies (CUEs) overlapped significantly between all OM pools. Compound type (e.g., natural versus PyOM) had approximately 6-fold less impact on predicted respiration rates than simulated carbon and oxygen limitations. Within PyOM, the metabolism of specific chemistries differed strongly between unlimited and oxygenlimited conditions – degradations of anhydrosugars, phenols, and polycyclic aromatic hydrocarbons (PAHs) were more favorable under oxygen limitation than other molecules. Notably, amino sugar-like, protein-like, and lignin-like PyOM had lower carbon use efficiencies relative to natural DOM of the same classes, indicating potential impacts in process-based model representations. Overall, our work illustrates how similar PyOM bioavailability may be to that of natural DOM in the river corridor, furthering our understanding of how PyOM may influence riverine biogeochemical cycling.