Submicron Aerosol Composition in Smoke Plumes from Wildfires in the Western United States as Determined from Aerosol Mass Spectrometry

We evaluate the performance of a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) in determining the chemical composition of sub-micron non-refractory aerosols in the dynamic environment of wildfire smoke plumes. An Aerodyne HR-TOF-AMS was deployed on the NSF/NCAR C-130 research aircraft during the Western Wildfire Experiment: Cloud Chemistry, Aerosol Absorption, Nitrogen (WE-CAN) study during July and August 2018 to provide in situ measurements of aerosol chemical composition. Here, we will examine the effects of the rapidly changing environmental conditions inside and outside the plume, such as changes in CO and CO2 mixing ratios, on the interpretation of AMS results. We will present the chemical composition of submicron aerosols within smoke plumes with an emphasis on sampling in the near-field where smoke is aged less than 2 hours. Finally, we will explore the use of black carbon, provided by concurrent measurements from single particle soot photometry (SP2), with biomass burning tracers in the HR-TOF-AMS mass spectra as tools to investigate the competing effects of oxidative chemistry and physical dilution on the evolution of the composition of aerosols in wildfire smoke over time.