AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Brown Carbon Lifetime and Chemistry Following Wildfires
HAVILAND FORRISTER, Jiumeng Liu, Eric Scheuer, Jack Dibb, Luke Ziemba, Kenneth Thornhill, Bruce Anderson, Glenn Diskin, Anne Perring, Joshua P. Schwarz, Pedro Campuzano-Jost, Douglas Day, Jose-Luis Jimenez, Athanasios Nenes, Rodney J. Weber, Georgia Institute of Technology
Abstract Number: 143 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Brown carbon (BrC) aerosol in the atmosphere absorbs light in the UV and visible wavelengths, and has the potential to have large climate forcing impacts. Most BrC is produced from biomass burning, but its lifecycle and atmospheric stability following emission from wildfires is largely unknown. Wildfires are projected to increase dramatically in a warmer and drier future climate. Therefore, ascertaining the extent to which BrC will remain in the atmosphere and affect light-absorption, and thus climate forcing, is crucial. Toward this end, we measured BrC collected on filters from plumes transported for over two days from two fires in the western USA, during the 2013 NASA SEAC4RS mission. Using measurements of organic aerosol mass (OA), black carbon mass (BC), BC coating thickness, aerosol absorption Angström exponent (AAE), oxygen-to-carbon ratio (O/C), and f60 (tracer of biomass burning primary OA), we determine that the BrC emitted from the wildfires was largely unstable. Based on the atmospheric transport time of the smoke calculated using HYSPLIT back trajectories, we found that BrC aerosol light absorption decreased exponentially after emission, with a half-life of 9 to 15 hours. Although most of the BrC was lost within a day, likely due to chemical loss and/or evaporation, a persistent fraction remained, which likely affects the background BrC levels most relevant for climate forcing. Though only the transport times of the two longest data sets could be calculated, we compare data from two other wildfire plumes from the NASA SEAC4RS mission to show BrC light absorption variability from wildfires, as correlated with O/C, f60, and AAE. We also explore the relationship between water-soluble and methanol-soluble BrC to understand the relationship between polarity and aging of light-absorbing compounds in the aerosol.