Characterization of Non-Methane Organic Gases in Wildfire Smoke by PTR-ToF-MS during the WE-CAN Field Campaign

Volatile organic compound (VOC) emissions from biomass burning are poorly understood relative to other sources due in part to the large variability and the difficulty inherent to sampling smoke. Early plume evolution of VOCs influences secondary organic aerosol (SOA) yields, ozone formation, and OH radical chemistry far downwind of a fire. To better characterize wildfire plume emissions and chemistry, we deployed a high-resolution proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) on the NSF/NCAR C-130 research aircraft during the collaborative Western wildfire Experiment for Cloud chemistry, Aerosol absorption and Nitrogen (WE-CAN) mission. PTR-ToF-MS is well suited for airborne measurements of VOC in wildfire smoke plumes due to its ability to collect real-time, high-resolution data for the full mass range of ionizable organic species, many of which remain uncharacterized or unidentified in the field. In this work, we will report on our VOC measurements from the WE-CAN research flights during summer 2018. We will compare PTR-ToF-MS results with co-measured species from complementary VOC instruments in the WE-CAN payload, such as NCAR’s trace online gas analyzer (TOGA) and advance whole air sampler (AWAS). We will then present emission ratios for some of the most common and abundant VOCs over different fuel types sampled during WE-CAN, comparing findings with recent lab and field campaigns. Finally, we will discuss how the overall oxidation state of organic gases evolve and how the calculated within-plume OH radical abundance and OH reactivity change in the first 24 hours of plume aging.