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

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.

Optimization of a Method for the Detection of Biomass-Burning Relevant VOCs in Urban Areas Using Thermal Desorption Gas Chromatography Mass Spectrometry

“…Nevertheless, using this sampling protocol these seven VOCs were observed in a few samples collected in Boise, Idaho, as a part of the NOAA FIREX AQ-2019 experiment discussed in later sections. Several previous studies [1,[15][16][17]29] have shown significant emissions of these oxygenated VOCs from biomass burning. In principle, measurements and the emission ratios of these additional seven oxygenated VOC smoke tracers could help estimate the age of a smoke plume [29,30].…”

Oxygenated Aromatic Compounds are Important Precursors of Secondary Organic Aerosol in Biomass-Burning Emissions

“…12,21,25 Ahern et al 12 found monoterpenes to be important for two conifers (i.e., black spruce, ponderosa pine) and furans to be important for grasses (i.e., wiregrass) while Bruns et al 21 and Stefenelli et al 25 found oxygenated aromatics and PAHs to be important for SOA from wood stoves. Lim et al (2019) found tight correlations between the SOA produced and the initial VOC mass, with stronger correlations observed for VOCs more volatile than monoterpenes. These earlier studies suggest that the dominant SOA precursors vary widely based on the fuel and there is a continued need to better understand these precursors across the diversity of fuel types found within the broad source category of biomass burning.…”

Atmospheric aging of small-scale wood combustion emissions (model MECHA 1.0) – is it possible to distinguish causal effects from non-causal associations?

“…These removed compounds were mainly instrumental background or compounds with very small concentration without any clear structure as a time series. Time series for the factors were calculated by sum score method, where the original data is multiplied directly with the loading values from EFA with possibly some threshold limit (Comrey, 1973). We selected absolute value of 0.3 as a threshold for the loadings, meaning any loading values smaller than that were suppressed to zero before the multiplication (Yong and Pearce, 2013).…”

“…There exists several chemical models such as Master Chemical Mechanism (MCM) (Jenkin et al, 1997;Saunders et al, 2003) and GECKO-A (Aumont et al, 2005), which comprise large amounts of chemical reactions and pre-determined reaction coefficients to replicate the evolution of the system. MCM has been recently applied to wood burning emissions by running the model with most important primary emission species to model the evolution of gas-phase species using smaller selection of reactions from the whole system (Coggon et al, 2019). Statistical Oxidation Model (SOM) is somewhere between one-quality models and explicit chemical models.…”