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Environmental Science & Technology








With the increased occurrences of wildfires worldwide, there has been an increase in scientific interest surrounding the chemistry of fire-derived "black" carbon (BC). Traditionally, wildfire research has assumed that condensed aromatic carbon (ConAC) is exclusively produced via combustion, and thus, ConAC is equated to BC. However, the lack of correlations between ConAC in soils or rivers and wildfire history suggests that ConAC may be produced non-pyrogenically. Here, we show quantitative evidence that this occurs during the oxidation of biomass with environmentally ubiquitous hydroxyl radicals. Pine wood boards exposed to iron nails and natural weather conditions for 12 years yielded a charcoal-like ConAC-rich material. ConAC was also produced during laboratory oxidations of pine, maple, and brown-rotted oak woods, as well as algae, corn root, and tree bark. Back-of-the-envelope calculations suggest that biomass oxidation could be producing massive non-pyrogenic ConAC fluxes to terrestrial and aquatic environments. These estimates (e.g., 163-182 Tg-ConAC/year to soils) are much higher than the estimated pyrogenic "BC" fluxes (e.g., 128 Tg-ConAC/year to soils) implying that environmental ConAC is primarily non-pyrogenic. This novel perspective suggests that wildfire research trajectories should shift to assessing non-pyrogenic ConAC sources and fluxes, developing new methods for quantifying true BC, and establishing a new view of ConAC as an intermediate species in the biogeochemical processing of biomass during soil humification, aquatic photochemistry, microbial degradation, or mineral-organic matter interactions. We also advise against using BC or pyrogenic carbon (pyC) terminologies for ConAC measured in environmental matrices, unless a pyrogenic source can be confidently assigned.


© 2024 The Authors.

This publication is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) License.

Data Availability

Article states: "Molecular formula catalogs and raw BPCA data have been published in the Mendeley Data Repository (doi: 10.17632/9mj4dvmbt5.2). Any other ancillary measurements used in this publication were provided in the manuscript or its Supporting Information. Parts of this work were also previously published as part of Aleksandar I. Goranov’s dissertation (doi: 10.25777/fpsv-4e28) (45) and are reused with the appropriate permissions."

Original Publication Citation

Goranov, A. I., Chen, H., Duan, J., Myneni, S. C. B., & Hatcher, P. G. (2024). Potentially massive and global non-pyrogenic production of condensed "black" carbon through biomass oxidation. Environmental Science & Technology, 58(6), 2750-2761.


0000-0002-5103-0838 (Goranov), 0000-0003-2460-838X (Chen)