PNNL

Abstract

Biomass-burning organic-aerosol emissions are known to exhibit semi-volatile behavior that impacts the organic-aerosol loading during plume transport. Therefore, improved speciation of intermediate and semi-volatile organic compounds (I/SVOCs) emitted during fires is needed to assess the competing effects of primary organic aerosol volatilization and secondary organic aerosol 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 run 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 volatilized primary organic aerosol, which was entirely attributed to oxygenated (or other heteroatomic) compounds.