FIREX 2018/2019 Volatile Organic Compounds (VOC) Measurements: Emissions, Factor Analysis, and Aging From Mobile Proton Transfer Reaction Mass Spectrometer

Better measurements and constraints of volatile organic compounds (VOCs) are critical to modeling the effects of increasingly frequent wildfires in the western USA on secondary organic aerosol formation and the oxidant budget. Using a Vocus Proton Transfer Reaction Mass Spectrometer (Vocus PTR) as well as Tunable Infrared Laser Direct Absorption Laser Spectroscopy (TILDAS) instruments on the Aerodyne Mobile Laboratory (AML) , seven different fires over two years (FIREX 2018 and 2019) were sampled providing extensive chemical composition and aging information of gaseous (VOCs , oxidized VOCs , trace gases ) and particulate (black carbon, organic carbon) emissions from fires . Several of these fires were sampled less than a mile away from burning fuel, providing extremely fresh smoke measurements . Emission ratios calculated from Vocus PTR measurements display statistically significant consistency with previous measurements of controlled fires in a laboratory setting. Within specific fires, chemically unique mass spectral signatures of smoldering and flaming are determined from factor analysis. Lastly, since our mobile platform sampled plumes across several distances, including directly adjacent from a fire, the effect of oxidative aging on gas phase species concentrations are characterized. Several photochemical aging markers and their reactivity with daytime and nighttime oxidants are investigated. These results are compared with in-situ aging experiments of fire plumes that are oxidized in an oxidation flow reactor.