Measurement report: Observations of long-lived volatile organic compounds from the 2019–2020 Australian wildfires during the COALA campaign

Abstract

Abstract. In 2019–2020, Australia experienced its largest wildfire season on record. Smoke covered hundreds of square kilometers across the southeastern coast and reached the site of the COALA-2020 (Characterizing Organics and Aerosol Loading over Australia) field campaign in New South Wales. Using a subset of nighttime observations made by a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS), we calculate emission ratios (ERs) and factors (EFs) for 15 volatile organic compounds (VOCs). We restrict our analysis to VOCs with sufficiently long lifetimes to be minimally impacted by oxidation over the ∼ 8 h between when the smoke was emitted and when it arrived at the field site. We use oxidized VOC to VOC ratios to assess the total amount of radical oxidation: maleic anhydride / furan to assess OH oxidation, and (cis-2-butenediol + furanone) / furan to assess NO3 oxidation. We examine time series of O3 and NO2 given their closely linked chemistry with wildfire plumes and observe their trends during the smoke event. Then we compare ERs calculated from the freshest portion of the plume to ERs calculated using the entire nighttime period. Finding good agreement between the two, we are able to extend our analysis to VOCs measured in more chemically aged portions of the plume. Our analysis provides ERs and EFs for six compounds not previously reported for temperate forests in Australia: acrolein (a compound with significant health impacts), methyl propanoate, methyl methacrylate, maleic anhydride, benzaldehyde, and creosol. We compare our results with two studies in similar Australian biomes, and two studies focused on US temperate forests. We find over half of our EFs are within a factor of 2.5 relative to those presented in Australian biome studies, with nearly all within a factor of 5, indicating reasonable agreement. For US-focused studies, we find similar results with over half our EFs within a factor of 2.5, and nearly all within a factor of 5, again indicating reasonably good agreement. This suggests that comprehensive field measurements of biomass burning VOC emissions in other regions may be applicable to Australian temperate forests. Finally, we quantify the magnitude attributable to the primary compounds contributing to OH reactivity from this plume, finding results comparable to several US-based wildfire and laboratory studies.

Airborne glyoxal measurements in the marine and continental atmosphere: comparison with TROPOMI observations and EMAC simulations

“…4; brown colour) are documented in the literature. On 12 November 2019, an aged (3-4 d old) biomass burning filament was detected in the upper troposphere and lower stratosphere over the Drake Passage around 57 • S and 67 • W that most probably originated from Australian bushfires (Kloss et al, 2021;Mouat et al, 2022). On this day, elevated glyoxal up to 83 ± 32 ppt was continuously measured during a 280 km long flight section around 11 km in altitude south of Patagonia (Fig.…”

Unexpected electrophiles in the atmosphere – anhydride nucleophile reactions and uptake to biomass burning emissions

“…To date, gas-phase phthalic anhydride ambient air measurements have not been reported, while maleic anhydride concentrations are sparsely reported. 23–61 Lee et al have performed ambient particle measurements showing variable concentrations of phthalic anhydride of ∼49.9 ± 47.7 ng m −3 . 62 The lack of ambient data is in part due to the anhydride concentration being negligible after plume dissipation, combined with requiring high resolution instrumentation for their detection which is typically not employed for routine analyses.…”

“…The predicted phthalic anhydride mixing ratio within our system is 4–10 ppb, which is closely associated with previous reports of ∼1–2 ppb for maleic anhydride in aged burn plumes. 23–61 However, the mixing ratio of maleic anhydride was estimated to be 2–7 ppm, lowering this concentration while maintaining reproducibility was challenging due to its high volatility. For this reason, only phthalic anhydride uptake coefficients are reported following.…”

Unexpected Electrophiles in the Atmosphere - Anhydride Nucleophile Reactions and Uptake to Biomass Burning Emissions

“…The predicted phthalic anhydride mixing ratio within our system is 4-10 ppb, which is closely associated with previous reports of ∼1-2 ppb for maleic anhydride in aged burn plumes. 23,24,53 However, the mixing ratio of maleic anhydride was estimated to be 2-7 ppm, lowering this concentration while maintaining reproducibility was challenging due to its high volatility. For this reason, only phthalic anhydride uptake coefficients are reported following.…”

“…To date, gas-phase phthalic anhydride ambient air measurements have not been reported, while maleic anhydride concentrations are sparsely reported. 23,24,53 Lee et al have performed ambient particle measurements showing variable concentrations of phthalic anhydride of ∼ 49.9±47.7 ng m −3 . 54 The lack of ambient data is in part due to the anhydride concentration being negligible after plume dissipation, combined with requiring high resolution instrumentation for their detection which is typically not employed for routine analyses.…”