Analyses of Gaseous Organic Compounds in Biomass Burning Smoke Samples Collected from Ground and Airborne Platforms during the Fire Influence on Regional and Global Environments Experiment (FIREX) Field Campaign

Abstract:

The nighttime chemistry in biomass burning (BB) plumes can influence local to regional air quality, but remains largely understudied. During the 2019 Fire Influence on Regional and Global Environments Experiment (FIREX) field experiment, gas-phase smoke samples were collected using dual-bed sorbent tubes from the Twin Otter aircraft and the Aerodyne Mobile Lab (AML). On both platforms, daytime and nighttime samples were collected to facilitate comparison of daytime and nighttime chemical conditions and the subsequent influence on secondary organic aerosol (SOA) formation. Samples were analyzed using two-dimensional gas chromatography with time-of-flight mass spectrometry. Compounds identified in the Twin Otter samples included: alkanes, alkenes, ketones, (oxygenated) aromatics, and phenols; particular attention has been given to terpenes and other compounds likely relevant for nighttime chemistry (e.g., furans and furfural). Trends in the gaseous organic compounds identified in the Twin Otter samples are being compared to measurements made using chemical ionization mass spectrometry, and used to understand downwind chemical evolution and diel trends in BB plumes. In samples from both the Twin Otter and AML platforms, terpenes were measured in relatively high concentrations and have previously been shown to exhibit clear chemical signatures, “fingerprints”, as a function of fuel type (e.g., pine, fir, shrub). Using data from the 2016 FIREX lab study, we developed a statistical method to identify fuel types using these unique chemical signatures. We have applied this method, along with traditional source apportionment methods, to identify fuel types sampled and their contributions to the FIREX AML samples. Measurement data from the AML, including particle phase mass and composition from nighttime oxidation flow reactor experiments, will be used with the results of the statistical analyses to assess the importance of fuel type and chemical conditions on SOA formation. Results from this work will be discussed in the context of better integrating field and laboratory data, as well as improving our understanding of the linkages between fuel types and chemical evolution of fire plumes during both daytime and nighttime chemical and meteorological conditions, including how each influences SOA formation.