Abstract
Abstract. Chamber oxidation experiments conducted at the Fire Sciences Laboratory in 2016 are evaluated to identify important chemical processes contributing to the hydroxy radical (OH) chemistry of biomass burning non-methane organic gases (NMOGs). Based on the decay of primary carbon measured by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS), it is confirmed that furans and oxygenated aromatics are among the NMOGs emitted from western United States fuel types with the highest reactivities towards OH. The oxidation processes and formation of secondary NMOG masses measured by PTR-ToF-MS and iodide-clustering time-of-flight chemical ionization mass spectrometry (I-CIMS) is interpreted using a box model employing a modified version of the Master Chemical Mechanism (v. 3.3.1) that includes the OH oxidation of furan, 2-methylfuran, 2,5-dimethylfuran, furfural, 5-methylfurfural, and guaiacol. The model supports the assignment of major PTR-ToF-MS and I-CIMS signals to a series of anhydrides and hydroxy furanones formed primarily through furan chemistry. This mechanism is applied to a Lagrangian box model used previously to model a real biomass burning plume. The customized mechanism reproduces the decay of furans and oxygenated aromatics and the formation of secondary NMOGs, such as maleic anhydride. Based on model simulations conducted with and without furans, it is estimated that furans contributed up to 10 % of ozone and over 90 % of maleic anhydride formed within the first 4 h of oxidation. It is shown that maleic anhydride is present in a biomass burning plume transported over several days, which demonstrates the utility of anhydrides as markers for aged biomass burning plumes.
Highlights
Biomass burning is a significant source of atmospheric nonmethane organic gases (NMOGs)
The NOx/NMOG ratio varied over several orders of magnitude (0.01–1.2) with NMOG loadings ranging from 90 to 900 ppb
Fires produced varying distributions of NMOGs owing to the extent of high- and lowtemperature pyrolysis, while NOx mixing ratios varied depending on fuel nitrogen content (Burling et al, 2010) and the extent of flaming combustion (Sekimoto et al, 2018)
Summary
Biomass burning is a significant source of atmospheric nonmethane organic gases (NMOGs). Field observations have shown that ozone enhancement ratios ( O3/ CO) may increase (e.g., 0.7 ppb ppb−1, Andreae et al, 1988; Mauzerall et al, 1998), decrease (e.g., −0.07 ppb ppb−1, Alvarado et al, 2010), or remain unchanged downwind of wildfires (Jaffe and Wigder, 2012). The extent of ozone production depends on multiple factors, including NMOG/NOx ratios, downwind meteorology, and incident solar radiation (Akagi et al, 2013; Jaffe et al, 2018). Primary NMOG speciation is largely driven by pyrolysis temperatures and fuel composition (e.g., Sekimoto et al, 2018; Hatch et al, 2015), whereas NOx emissions generally increase with increased flaming combustion and greater fuel nitrogen content (Burling et al, 2010)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
