Biomass Burning Emissions and Atmospheric Aging of Aerosols – Results from the BBOP Campaign
Authors
Qi Zhang — University of California, Davis
Shan Zhou — University of California, Davis
Sonya Collier — University of California
Daniel Jaffe — University of Washington
Jonathan Hee — University of Washington, Seattle
Nicole Briggs — Gradient Corp
Timothy B Onasch — Aerodyne Research, Inc.
Larry Kleinman — Brookhaven National Laboratory
Arthur J Sedlacek — Brookhaven National Laboratory
Category
Secondary organic aerosol
Description
Biomass burning (BB) is one of the most important contributors to atmospheric aerosols on a global scale and wildfires are a large source of emissions that impact regional air quality and global climate. However, wildfire emissions and their optical and microphysical properties are highly variable and are strongly dependent on combustion processes and fuel types. In this study, wildfire emissions in the Pacific Northwest region of the United States were characterized using real-time measurements near their sources using an aircraft, and farther downwind from a fixed ground site located at the Mt. Bachelor Observatory (~ 2700 m a.s.l.) in summer 2013 during the DOE Biomass Burning Observation Project (BBOP) field campaign. Use an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) coupled with a thermodenuder, we characterized the size resolved composition and volatility profiles of non-refractory submicron aerosol particles (NR-PM1) during periods affected by transported BB emissions. Episodes of high concentrations of NR-PM1 (up to ~140 µg/m3) were observed, during which organic aerosol (OA) dominated the PM composition along with elevated levels of anhydrosugar (e.g., levoglucosan). Three distinctive BBOA factors were identified by Positive Matrix Factorization (PMF): a fresh BBOA-I factor that correlates well with ammonium nitrate; an intermediately oxidized BBOA-II, and a highly oxidized BBOA-III that chemically very similar to low-volatility oxygenated organic aerosol (LV-OOA). During persistent BB plume events from fixed fire sources, fresh BBOA-I initially dominated the OA composition, but decreased as the more oxidized BBOA-II increased while BBOA-III remained unchanged. These events shed light on the chemical transformation of BBOA during atmospheric aging. The temporal variation of different BBOA factors as well as tracer species for SOA from BB precursors shed lights on SOA formation processes in BB plumes.
