AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Properties and Evolution of Biomass Burning Organic Aerosol from Wildfires in the Western U.S.
Shan Zhou, Sonya Collier, Timothy Onasch, Daniel Jaffe, Lawrence Kleinman, Arthur J. Sedlacek, QI ZHANG, University of California, Davis
Abstract Number: 443 Working Group: Aerosol Chemistry
Abstract Wildfires are a large source of primary organic aerosol (POA) and volatile organic compounds (VOCs) that can be oxidized to form secondary organic aerosol (SOA). However, the chemical properties and the formation and atmospheric aging of these organic aerosols (OA) are still poorly understood and constrained. In this study, a suite of real-time instruments, including high-resolution aerosol mass spectrometers, were deployed at the Mt. Bachelor Observatory (2763 m a.s.l.) – a high-altitude ground site located in Central Oregon – and onboard the Gulfstream-1 aircraft during the DOE-sponsored Biomass Burning Observation Period (BBOP). Our goal was to study the emissions and atmospheric aging of BB particles from wildfires in the western US. Well-defined smoke plumes that span a range of transport time (1 – 45 h) were identified based on MODIS fire hotspot information and HYSPLIT trajectory. The cumulative solar radiation (CSR) that each smoke plume was exposed to over the course of transport was estimated and used as an indicator for photochemical aging. We found that the enhancement ratios of OA relative to CO (∆OA/∆CO) were independent of CSR, indicating negligible net photochemical production of OA in wildfire plumes observed in this study. However, the enhancement ratios of AMS tracer ion for levoglucosan, C2H4O2+, (∆C2H4O2+/∆CO) and the fresh BBOA component (∆BBOAf/∆CO) decreased with CSR, while that of the aged BBOA components (∆BBOAa/∆CO) increased with CSR. In addition, our thermodenuder measurements indicate that the fresh BBOA was more volatile than the aged BBOA. These results indicate that volatilization, photooxidation, and secondary formation of BBOA occurred simultaneously in wildfire plumes after emission and that atmospheric aging and oxidation significantly changes the chemical composition of BBOA. These processes likely influence both the properties and the lifetime of BB particles, and therefore their effects on climate and health.