An improved representation of fire non-methane organic gases (NMOGs) in models: emissions to reactivity

Abstract

Abstract. Fires emit a substantial amount of non-methane organic gases (NMOGs), the atmospheric oxidation of which can contribute to ozone and secondary particulate matter formation. However, the abundance and reactivity of these fire NMOGs are uncertain and historically not well constrained. In this work, we expand the representation of fire NMOGs in a global chemical transport model, GEOS-Chem. We update emission factors to Andreae (2019) and the chemical mechanism to include recent aromatic and ethene and ethyne model improvements (Bates et al., 2021; Kwon et al., 2021). We expand the representation of NMOGs by adding lumped furans to the model (including their fire emission and oxidation chemistry) and by adding fire emissions of nine species already included in the model, prioritized for their reactivity using data from the Fire Influence on Regional to Global Environments (FIREX) laboratory studies. Based on quantified emissions factors, we estimate that our improved representation captures 72 % of emitted, identified NMOG carbon mass and 49 % of OH reactivity from savanna and temperate forest fires, a substantial increase from the standard model (49 % of mass, 28 % of OH reactivity). We evaluate fire NMOGs in our model with observations from the Amazon Tall Tower Observatory (ATTO) in Brazil, Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) and DC3 in the US, and Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) in boreal Canada. We show that NMOGs, including furan, are well simulated in the eastern US with some underestimates in the western US and that adding fire emissions improves our ability to simulate ethene in boreal Canada. We estimate that fires provide 15 % of annual mean simulated surface OH reactivity globally, as well as more than 75 % over fire source regions. Over continental regions about half of this simulated fire reactivity comes from NMOG species. We find that furans and ethene are important globally for reactivity, while phenol is more important at a local level in the boreal regions. This is the first global estimate of the impact of fire on atmospheric reactivity.

Space-Based Observations of Ozone Precursors within California Wildfire Plumes and the Impacts on Ozone-NOx-VOC Chemistry

“…Indeed, we found that GEOS-Chem tends to underestimate the HCHO enhancement in plumes older than 10 h (Figure a), which is likely due to the contribution from those missing fire VOCs, or inaccurate representation of the later-generation VOC degradation products. Expansion of VOC species in GEOS-Chem could improve the representation of VOC reactivity, and it is expected that the relative contributions of primary emissions to HCHO will be even smaller if we include more HCHO precursors. Hundreds of VOC species are known to be present in fire plumes, and many of them remain unidentified .…”

“…We distributed 35% biomass burning emissions in the first ten sigma layers above the boundary layer, and the other 65% within the boundary layer . The standard GEOS-Chem (v12.7.0) does not include biomass burning emissions and chemistry of ethene (C 2 H 4 ), but C 2 H 4 is a large contributor to organic reactivity in fire plumes . We incorporated the chemistry of C 2 H 4 following Kwon et al, and it has been incorporated in standard GEOS-Chem since version 13.3.0.…”

“…59 The standard GEOS-Chem (v12.7.0) does not include biomass burning emissions and chemistry of ethene (C 2 H 4 ), but C 2 H 4 is a large contributor to organic reactivity in fire plumes. 60 We incorporated the chemistry of C 2 H 4 following Kwon et al, 61 and it has been incorporated in standard GEOS-Chem since version 13.3.0. To assess the influence of biomass burning emissions, we ran three additional simulations that (1) turn off total biomass burning emissions (Sim No_Fire ); (2) turn off biomass burning primary emissions of HCHO (Sim No_HCHO ); and (3) turn off biomass burning emissions of C 2 H 4 (Sim No_C2H4 ).…”

Atmospheric OH reactivity in the western United States determined from comprehensive gas-phase measurements during WE-CAN

“…Consequently, CTMs only implement simplied chemistry for a handful (typically <30) of the most studied individual and lumped species, which were oen developed and evaluated for relatively well-studied environments such as urban areas, forests, and to a lesser extent the remote/clean troposphere. 24,30,[37][38][39][40] Recent work suggests the GEOS-Chem CTM underpredicts biogenic VOC reactivity ux by 40-60% in forest environments, with major uncertainties related to a few select known/modeled VOCs, rather than unrepresented species. 30 How well these modeled species represent the most important individual OH sinks in wildre smoke has yet to be assessed.…”

Evolution of Organic Carbon in the Laboratory Oxidation of Biomass Burning Emissions

“…Biomass burning (BB) is a major source of reactive organic carbon, both in the form of aerosol and non-methane organic gases (NMOG), to the atmosphere (Carter et al, 2022;Andreae et al, 1988;Yokelson et al, 2009;Akagi et al, 2013;Bond et al, 2004;Liu et al, 2016). BB emissions can have large impacts on air quality and climate across a range of scales, due both to primary species and to their transformation to secondary species such as ozone and secondary organic aerosol (SOA) (Cubison et al, 2011;Decarlo et al, 2010;Grieshop et al, 2009;Hennigan et al, 2011;Ortega et al, 2013;Tkacik et al, 2017;Yokelson et al, 2009;Hobbs et al, 2003;Akagi et al, 2013;Bourgeois et al, 2021;Hobbs et al, 1997;Liu et al, 2014).…”