Reconciling the total carbon budget for boreal forest wildfire emissions using airborne observations

Abstract

Abstract. Wildfire impacts on air quality and climate are expected to be exacerbated by climate change with the most pronounced impacts in the boreal biome. Despite the large geographic coverage, there is a lack of information on boreal forest wildfire emissions, particularly for organic compounds, which are critical inputs for air quality model predictions of downwind impacts. In this study, airborne measurements of 250 compounds from 15 instruments, including 228 non-methane organics compounds (NMOG), were used to provide the most detailed characterization, to date, of boreal forest wildfire emissions. Highly speciated measurements showed a large diversity of chemical classes highlighting the complexity of emissions. Using measurements of the total NMOG carbon (NMOGT), the ΣNMOG was found to be 46.2 % of NMOGT, of which, the intermediate- and semi-volatile organic compounds (I/SVOCs) were estimated to account for 7.4 %. These estimates of I/SVOC emission factors expand the volatility range of NMOG typically reported. Despite extensive speciation, a substantial portion of NMOGT remained unidentified (46.4 %), with expected contributions from more highly-functionalized VOCs and I/SVOCs. The emission factors derived in this study improve wildfire chemical speciation profiles and are especially relevant for air quality modelling of boreal forest wildfires. These aircraft-derived emission estimates were further linked with those derived from satellite observations demonstrating their combined value in assessing variability in modelled emissions. These results contribute to the verification and improvement of models that are essential for reliable predictions of near-source and downwind pollution resulting from boreal forest wildfires.

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

“…While fires emit a significant amount of NMOGs (∼ 100-200 Tg yr −1 ) (Akagi et al, 2011;Yokelson et al, 2008;Andreae and Merlet, 2001), second only to biogenic sources globally (∼ 1000 Tg yr −1 ) (Guenther et al, 2012), modeling efforts, particularly at the global scale, have historically represented only a modest subset of these emissions and their reactivity. This is in part because a large number of reactive fire NMOGs remain unidentified (Kumar et al, 2018;Hayden et al, 2022;Akagi et al, 2011). While progress has been made on measuring emissions of many fire NMOGs, these measurements have not yet been incorporated into models with global coverage.…”

An Improved Representation of Fire Non-Methane Organic Gases (NMOGs) in Models: Emissions to Reactivity

“…While fires emit a significant amount of NMOGs (> 400 Tg yr -1 ) (Akagi et al, 2011;Yokelson et al, 2008), second only to biogenic sources globally (~1000 Tg yr -1 ) (Guenther et al, 2012), modeling efforts, particularly at the global scale, have historically represented only a modest subset of these emissions and their reactivity. This is in part because a large number of reactive 95 fire NMOGs remain unidentified (Kumar et al, 2018;Hayden et al, 2022;Akagi et al, 2011).…”