Abstract. Biomass-burning organic-aerosol (OA) emissions are known to exhibit semi-volatile behavior that impacts OA loading during plume transport. Because such semi-volatile behavior depends in part on OA composition, improved speciation of intermediate and semi-volatile organic compounds (I/SVOCs) emitted during fires is needed to assess the competing effects of primary OA volatilization and secondary OA production. In this study, we sampled 18 laboratory fires in which a range of fuel types were burned. Emitted I/SVOCs were collected onto Teflon filters and solid-phase extraction (SPE) disks to characterize particulate and gaseous I/SVOCs, respectively. Derivatized filter extracts were analyzed using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC × GC − TOFMS). Quality control tests were performed using biomass-burning relevant standards and demonstrate the utility of SPE disks for untargeted analysis of air samples. The speciation profiles of I/SVOCs in coniferous fuel-derived smoke samples determined by GC × GC − TOFMS were well correlated with each other, but poorly correlated with other fuel types (e.g., herbaceous and chaparral fuels). Benzenediol isomers were also shown to display fuel-dependent emissions. Differences in gas-particle partitioning of the benzenediol isomers were captured using combined Teflon and SPE filter data, with hydroquinone significantly less volatile than catechol. Additionally, the speciated volatility distribution of I/SVOCs in smoke from a rotten-log fire was estimated to evaluate the composition of potentially volatilized primary OA, which was entirely attributed to oxygenated (or other heteroatomic) compounds. Because the chemistry of such compounds has not been extensively studied, more work is needed to assess the relative importance of gas-phase vs. heterogeneous oxidation pathways for biomass-burning-derived I/SVOCs.
Supplementary material to "Measurements of I/SVOCs in biomass-burning smoke using solid-phase extraction disks and two-dimensional gas chromatography"
