Investigating fire-induced ozone production from local to global scales

Abstract. Tropospheric ozone (O3) production from wildfires is highly uncertain; previous studies have identified both production and loss of O3 in fire-influenced air masses. To capture the total ozone production attributable to a smoke plume, we bridge the gap between near-field fire plume chemistry and aged smoke in the remote troposphere. Using airborne measurements from several major campaigns, we find that fire-ozone production increases with age, with a regime transition from NOx-saturated to NOx-limited conditions, showing that O3 production in well-aged plumes is largely controlled by nitrogen oxides (NOx). Observations in fresh smoke demonstrate that suppressed photochemistry reduces O3 production by ∼ 70 % in units of ppb Ox (O3 + NO2) per ppm CO in the near-field (age < 20 h). We demonstrate that anthropogenic NOx injection into VOC-rich fire plumes drives additional O3 production, sometimes exceeding 50 ppb above background. Using a box model, we explore the evolving sensitivity of O3 production to fire emissions and chemical parameters. We demonstrate the importance of aerosol-induced photochemical suppression over heterogeneous HO2 uptake, validate HONO's importance as an oxidant precursor, and confirm evolving NOx sensitivity. We evaluate GEOS-Chem's performance against these observations, finding the model captures fire-induced O3 enhancements at older ages but overestimates near-field enhancements, fails to capture the magnitude and variability of fire emissions, and does not capture the chemical regime transition. These discrepancies drive biases in normalized ozone production (ΔO3/ΔCO) across plume lifetime, though the model generally captures observed absolute O3 enhancements in fire plumes. GEOS-Chem attributes 2.4 % of the global tropospheric ozone burden and 3.1 % of surface ozone concentrations to fire emissions in 2020, with stronger impacts in regions of frequent burning.

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Publication Details

Journal
Atmospheric chemistry and physics
Published
2025-11-28
DOI
https://doi.org/10.5194/acp-25-17107-2025
Primary Topic
Atmospheric chemistry and aerosols
Type
article
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article

Investigating fire-induced ozone production from local to global scales

Ilann Bourgeois, Lu Xu, Benjamin A. Nault, Samuel R. Hall et al.
Atmospheric chemistry and physics
Atmospheric chemistry and aerosols
article

Investigating fire-induced ozone production from local to global scales

Ilann Bourgeois, Lu Xu, Benjamin A. Nault, Samuel R. Hall, I‐Ting Ku, Joel A. Thornton, Alan Fried, Amy P. Sullivan, Pedro Campuzano‐Jost, Matthew Mitchell Coggon, D. R. Blake, Armin Wisthaler, Jeff Peischl, F. Flocke, Brett B. Palm, Lu Hu, Jose Luis Jimenez, Jeffrey L. Collett, Georgios I. Gkatzelis, I. B. Pollack, Joseph Palmo, Colette L. Heald, Carsten Warneke
article en

Abstract

Abstract. Tropospheric ozone (O3) production from wildfires is highly uncertain; previous studies have identified both production and loss of O3 in fire-influenced air masses. To capture the total ozone production attributable to a smoke plume, we bridge the gap between near-field fire plume chemistry and aged smoke in the remote troposphere. Using airborne measurements from several major campaigns, we find that fire-ozone production increases with age, with a regime transition from NOx-saturated to NOx-limited conditions, showing that O3 production in well-aged plumes is largely controlled by nitrogen oxides (NOx). Observations in fresh smoke demonstrate that suppressed photochemistry reduces O3 production by ∼ 70 % in units of ppb Ox (O3 + NO2) per ppm CO in the near-field (age < 20 h). We demonstrate that anthropogenic NOx injection into VOC-rich fire plumes drives additional O3 production, sometimes exceeding 50 ppb above background. Using a box model, we explore the evolving sensitivity of O3 production to fire emissions and chemical parameters. We demonstrate the importance of aerosol-induced photochemical suppression over heterogeneous HO2 uptake, validate HONO's importance as an oxidant precursor, and confirm evolving NOx sensitivity. We evaluate GEOS-Chem's performance against these observations, finding the model captures fire-induced O3 enhancements at older ages but overestimates near-field enhancements, fails to capture the magnitude and variability of fire emissions, and does not capture the chemical regime transition. These discrepancies drive biases in normalized ozone production (ΔO3/ΔCO) across plume lifetime, though the model generally captures observed absolute O3 enhancements in fire plumes. GEOS-Chem attributes 2.4 % of the global tropospheric ozone burden and 3.1 % of surface ozone concentrations to fire emissions in 2020, with stronger impacts in regions of frequent burning.

Atmospheric chemistry and physicsVol. 25(22)
NSF National Center for Atmospheric Research (US), Johns Hopkins University (US), Cooperative Institute for Research in Environmental Sciences (US), Forschungszentrum Jülich (DE), Institute of Arctic and Alpine Research (US), University of Oslo (NO), University of Colorado Boulder (US), Universität Innsbruck (AT), University of Washington (US), University of California, Irvine (US), Washington University in St. Louis (US), ETH Zurich (CH), Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (FR), Aerodyne Research (US), NOAA Chemical Sciences Laboratory (US), NSF NCAR Atmospheric Chemistry Observations & Modeling (US), Massachusetts Institute of Technology (US), University of Montana (US), Université Savoie Mont Blanc (FR), Colorado State University (US)
Openalex Percentile: Top 58%
Atmospheric chemistry and aerosols
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