Abstract
Abstract. We deployed a high-resolution proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) to measure biomass-burning emissions from peat, crop residue, cooking fires, and many other fire types during the fourth Fire Lab at Missoula Experiment (FLAME-4) laboratory campaign. A combination of gas standard calibrations and composition sensitive, mass-dependent calibration curves was applied to quantify gas-phase non-methane organic compounds (NMOCs) observed in the complex mixture of fire emissions. We used several approaches to assign the best identities to most major "exact masses", including many high molecular mass species. Using these methods, approximately 80–96% of the total NMOC mass detected by the PTR-TOF-MS and Fourier transform infrared (FTIR) spectroscopy was positively or tentatively identified for major fuel types. We report data for many rarely measured or previously unmeasured emissions in several compound classes including aromatic hydrocarbons, phenolic compounds, and furans; many of these are suspected secondary organic aerosol precursors. A large set of new emission factors (EFs) for a range of globally significant biomass fuels is presented. Measurements show that oxygenated NMOCs accounted for the largest fraction of emissions of all compound classes. In a brief study of various traditional and advanced cooking methods, the EFs for these emissions groups were greatest for open three-stone cooking in comparison to their more advanced counterparts. Several little-studied nitrogen-containing organic compounds were detected from many fuel types, that together accounted for 0.1–8.7% of the fuel nitrogen, and some may play a role in new particle formation.
Highlights
Biomass burning (BB) injects large amounts of primary, fine carbonaceous particles and trace gases into the global atmosphere and significantly impacts its physical and chemical properties (Crutzen and Andreae, 1990; Bond et al, 2004, 2013)
In addition to the comparisons considered in Stockwell et al (2014), we find that our emission factors (EFs) in Table S3 are consistent with additional, recent field studies including Kudo et al (2014) for Chinese crop residue fires and Geron and Hays (2013) for North Carolina (NC) peat fires
The most abundant species at that exact mass is listed with likely contributions to the total signal from the secondary species listed in column 5
Summary
Biomass burning (BB) injects large amounts of primary, fine carbonaceous particles and trace gases into the global atmosphere and significantly impacts its physical and chemical properties (Crutzen and Andreae, 1990; Bond et al, 2004, 2013). While BB emissions are recognized as the second largest global atmospheric source of gas-phase non-methane organic compounds (NMOCs) after biogenic emissions, a significant portion of the higher molecular weight species remains unidentified (Christian et al, 2003; Warneke et al, 2011; Yokelson et al, 2013). NMOCs impact smoke evolution by rapid formation of secondary organic aerosols (SOA) and secondary gases including photochemical ozone (O3) (Reid et al, 1998; Trentmann et al, 2005; Alvarado and Prinn, 2009; Yokelson et al, 2009; Vakkari et al, 2014). Measurements capable of identifying and quantifying rarely measured and presently unidentified emissions of NMOCs, in particular the chemically complex low volatility fraction, are vital for advancing current understanding of the BB impact on air quality and climate
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