AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Mass Absorption and Scattering Cross Sections of Brown Carbon Aerosol from Smoldering Biomass Combustion
NISHIT SHETTY, Benjamin Sumlin, Yuli W. Heinson, Wei Min Hao, Jay Turner, Brent Williams, Rajan Chakrabarty, Washington University in St. Louis
Abstract Number: 534 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Forest fires and biomass burning are significant contributors to atmospheric aerosol and trace gas emissions in many ecosystems, especially those in the boreal, arctic and tropical regions. A lot is known about the gaseous emissions from these fires, however, until recently, there has been little knowledge of the aerosol emission from fires in these regions. The amount and type of carbon released from these fires has a high dependence on combustion conditions and recent studies have shown that the smoldering (low temperature) phase of combustion release aerosols which are predominantly brown carbon (BrC) – a class of organic carbon absorbing light in the shorter visible wavelengths – along with a negligible amount of black carbon. In this study, we have simulated wildfires in our laboratory using different North American wildland fuels under varying smoldering combustion conditions, and measured the optical properties of the emitted BrC aerosols in-situ using multi-wavelength integrating photoacoustic nephelometers. The generated aerosols were also collected on filters to perform gravimetric studies for the quantification of mass. In this talk, I will discuss in detail our findings on the mass absorption and scattering cross-sections (MAC and MSC) of BrC aerosols as a function of fuel type, fuel-moisture-content, and combustion conditions. Initial findings show that the MAC of these aerosols have a strong dependence on wavelength ranging from 0.2 to 0.65 m2/g for 375nm and drop sharply to around 0.05 to 0.1 m2/g for 532nm. The mass scattering cross sections however, remained relatively constant in the given wavelength range and showed little to no dependence on wavelength from 375nm to 532nm.