Primary emissions of glyoxal and methylglyoxal from laboratory measurements of open biomass burning

Atmos. Chem. Phys., 18, 15451–15470, 2018 https://doi.org/10.5194/acp-18-15451-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Primary emissions of glyoxal and methylglyoxal from laboratory measurements of open biomass burning Kyle J. Zarzana1,2,a , Vanessa Selimovic3 , Abigail R. Koss1,2,4,b , Kanako Sekimoto1,2,5 , Matthew M. Coggon1,2 , Bin Yuan1,2,c , William P. Dubé1,2 , Robert J. Yokelson3 , Carsten Warneke1,2 , Joost A. de Gouw1,2,4 , James M. Roberts1 , and Steven S. Brown1,4 1 NOAA Earth System Research Laboratory (ESRL) Chemical Sciences Division, Boulder, CO 80305, USA Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309, USA 3 Department of Chemistry and Biochemistry, University of Montana, Missoula, MT 59812, USA 4 Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, CO 80309, USA 5 Graduate School of Nanobioscience, Yokohama City University, Yokohama, Kanagawa 236-0027, Japan a now at: Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, CO 80309, USA b now at: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02142, USA c now at: Institute of Environment and Climate Research, Jinan University, Guangzhou 510632, China 2 Cooperative Correspondence: Steven S. Brown () Received: 24 May 2018 – Discussion started: 13 June 2018 Revised: 26 September 2018 – Accepted: 27 September 2018 – Published: 26 October 2018 Abstract. We report the emissions of glyoxal and methylglyoxal from the open burning of biomass during the NOAAled 2016 FIREX intensive at the Fire Sciences Laboratory in Missoula, MT. Both compounds were measured using cavity-enhanced spectroscopy, which is both more sensitive and more selective than methods previously used to determine emissions of these two compounds. A total of 75 burns were conducted, using 33 different fuels in 8 different categories, providing a far more comprehensive dataset for emissions than was previously available. Measurements of methylglyoxal using our instrument suffer from spectral interferences from several other species, and the values reported here are likely underestimates, possibly by as much as 70 %. Methylglyoxal emissions were 2–3 times higher than glyoxal emissions on a molar basis, in contrast to previous studies that report methylglyoxal emissions lower than glyoxal emissions. Methylglyoxal emission ratios for all fuels averaged 3.6 ± 2.4 ppbv methylglyoxal (ppmv CO)−1 , while emission factors averaged 0.66 ± 0.50 g methylglyoxal (kg fuel burned)−1 . Primary emissions of glyoxal from biomass burning were much lower than previous laboratory measurements but consistent with recent measurements from aircraft. Glyoxal emission ratios for all fuels averaged 1.4 ± 0.7 ppbv glyoxal (ppmv CO)−1 , while emission factors averaged 0.20±0.12 g glyoxal (kg fuel burned)−1 , values that are at least a factor of 4 lower than assumed in previous estimates of the global glyoxal budget. While there was significant variability in the glyoxal emission ratios and factors between the different fuel groups, glyoxal and formaldehyde were highly correlated during the course of any given fire, and the ratio of glyoxal to formaldehyde, RGF , was consistent across many different fuel types, with an average value of 0.068 ± 0.018. While RGF values for fresh emissions were consistent across many fuel types, further work is required to determine how this value changes as the emissions age. 1 Introduction In addition to the large primary emissions of gases and particulate matter, the secondary chemistry that occurs downwind of fires can play an important role in numerous atmospheric processes. Ozone (O3 ), peroxy nitrates such as acetyl peroxynitrate (PAN), and organic aerosol are frequently enhanced in downwind fire plumes (e.g., Yokelson et al., 2009; Akagi et al., 2012; Alvarado et al., 2015; Liu et al., 2016), and in Published by Copernicus Publications on behalf of the European Geosciences Union. 15452 urban areas influenced by biomass burning, emissions from fires have been shown to increase O3 above the 70 ppbv standard set by the EPA (Brey and Fischer, 2016; Gong et al., 2017). Modeling of the chemistry of biomass burning plumes has found that carbonyls such as formaldehyde, methylglyoxal, and 2,3-butanedione play a large role in the formation of both O3 and PAN (Mason et al., 2001; Müller et al., 2016), either through reactions with hydroxyl radicals or photolysis. Carbonyl photolysis leading to O3 production has also been observed in other regions, such as oil and natural gas producing basins (Edwards et al., 2014). In addition to contributing to O3 formation, photolysis of carbonyls such as acetone and methylglyoxal can lead to the formation of PAN (Fischer et al., 2014; Müller et al., 2016). Understanding the impact of carbonyls on fire plume chemistry requires accurate measurements of emissions of these compounds, but those data are lacking for several carbonyl species, particularly small α-dicarbonyls such as glyoxal and methylglyoxal. Along with glyoxal and methylglyoxal, numerous other carbonyl species such as formaldehyde have been detected in fire plumes (e.g., Akagi et al., 2011; Stockwell et al., 2015; Koss et al., 2018). While methylglyoxal’s absorption cross section is relatively weak and unstructured, the cross sections of glyoxal and formaldehyde in the visible and ultraviolet respectively are large and structured, enabling the detection of those two molecules from space using remote sensing instruments such as the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY, Wittrock et al., 2006; Myriokefalitakis et al., 2008), the Global Ozone Monitoring Experiment-2 (GOME-2, Lerot et al., 2010), the Ozone Monitoring Instrument (OMI, Alvarado et al., 2014; Chan Miller et al., 2014), or the Tropospheric Emissions: Monitoring Pollution Instrument (TEMPO, Zoogman et al., 2017). The column abundances of glyoxal and formaldehyde are enhanced in regions influenced by biomass burning (Chan Miller et al., 2014), but the main source of both molecules globally is oxidation of larger volatile organic compounds (VOCs) (Shim et al., 2005; Fu et al., 2008; Fortems-Cheiney et al., 2012). The relative yields of glyoxal and formaldehyde depend in part on the precursor VOC, and the ratio of glyoxal to formaldehyde, RGF , is higher in regions dominated by emissions of aromatic VOCs than it is in regions dominated by emissions of isoprene (Chan Miller et al., 2016; Kaiser et al., 2015). RGF has been proposed as a metric for examining VOC chemistry from space (Vrekoussis et al., 2010; Chan Miller et al., 2014; Kaiser et al., 2015), as glyoxal and formaldehyde have similar atmospheric lifetimes with respect to photolysis and OH (∼ 3 h), but they have different yields from VOC oxidation. However, do (...truncated)