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

Abstract

Abstract. We report the emissions of glyoxal and methylglyoxal from the open burning of biomass during the NOAA-led 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.

OH chemistry of non-methane organic gases (NMOGs) emitted from laboratory and ambient biomass burning smoke: evaluating the influence of furans and oxygenated aromatics on ozone and secondary NMOG formation

“…C 4 H 4 O 3 −H + could be 5-hydroxy-2(5H)-furanone (or simply hydroxy furanone), its tautomer malealdehydic acid, or succinic anhydride, whereas C 4 H 8 O 2 −H + is likely a C 4 hydroxy carbonyl (see Sect. 3.1 and) Liu et al, 1999;Bierbach et al, 1994Bierbach et al, , 1995Alvarez et al, 2009;Aschmann et al, 2011Aschmann et al, , 2014Strollo and Ziemann, 2013;Zhao and Wang, 2017). Due to uncertainties in these assignments, calibration factors for these species are calculated using estimated proton transfer rate constants derived from molecular formula relationships (uncertainty to within a factor of 2, Sekimoto et al, 2017).…”

“…2), it is likely that these species are formed from the oxidation of furans, oxygenated aromatics, or other fastreacting NMOGs with C ≥ 4. Several studies have investigated the oxidation of furan species and shown that hydroxy furanone + tautomer (C 4 H 4 O 3 ) and methyl hydroxy furanone + tautomer (C 5 H 6 O 3 ) are major products formed from the oxidation of furfural, furan, 2-methylfuran, and 2,5dimethylfuran (e.g., Bierbach et al, 1994Bierbach et al, , 1995Alvarez et al, 2009;Aschmann et al, 2011Aschmann et al, , 2014Strollo and Ziemann, 2013;Zhao and Wang, 2017). Secondary NMOGs measured from the OH chemistry of oxygenated aromatic species are largely carbon-retaining (C ≥ 6), though C 4 H 4 O 4 ring fragments have been measured in low-NO x catechol oxidation (Yee et al, 2013).…”

“…Hartikainen et al (2018), for example, found that furans and phenolic compounds were among the most reactive NMOGs emitted from logwood emissions. The detailed chemical mechanisms of these compounds have been studied in single-component systems (Bierbach et al, 1995;Alvarez et al, 2009;Aschmann et al, 2011Aschmann et al, , 2014Zhao and Wang, 2017;Yee et al, 2013;Lauraguais et al, 2014;Finewax et al, 2018); however, these mechanisms have not been widely implemented into models of biomass burning smoke. Müller et al (2016) included simple mechanisms for furan and furfural; however, other major furan species, such as 2-methylfuran, 2,5-dimethylfuran, and 5-methylfurfural, were omitted.…”

Isotopic characterization of nitrogen oxides (NO<sub>x</sub>), nitrous acid (HONO), and nitrate (NO<sub>3</sub><sup>−</sup>(p)) from laboratory biomass burning during FIREX

“…(CES) Zarzana et al, 2018), and proton-transfer-reaction time-of-flight 278 mass spectrometer (PTR-ToF). Inlet ports of CES and PTR-ToF were placed 5' apart 279…”

“…Air was sampled directly 324 from stack at a height of 15 m above the fuel bed through a 1 m length of ¼" O.D. Teflon 325 (FEP) tubing as described inZarzana et al (2018). The residence time in the inlet and 326 sample cells was < 1 s. Comparison between the ACES HONO and an open path FTIR 327…”