Chemical Composition and Optical Properties of Laboratory-generated Biomass Burning Organic Aerosols
FELIPE RIVERA-ADORNO, Jay Tomlin, Theo Paik, August Li, Kyla Siemens, Zezhen Cheng, Nurun Nahar Lata, Ryan Moffet, Matthew Fraund, Swarup China, Rajan K. Chakrabarty, Alexander Laskin,
Purdue University Abstract Number: 495
Working Group: Carbonaceous Aerosol
AbstractBiomass burning organic aerosols (BBOA) impact Earth’s climate directly by scattering and absorbing sun light, and indirectly by modifying processes controlling cloud formation and lifecycles. This alteration to our planet’s climate is highly influenced by variability in the chemical composition, morphology, and mixing states of individual BBOA particles. In this work, four types of biomass fuels (i.e., grass, sage, peat, and pine) were burned in a laboratory combustion chamber to mimic BBOA representative of North American wildfires. BBOA samples were then collected using a cascade impactor for further single-particle chemical imaging. Samples of individual particles were probed using a computer-controlled scanning electron microscope coupled with energy dispersive X-ray microanalysis (CCSEM/EDX), which provided information on the particle-types determined based on the elemental composition and morphology. Complementary synchrotron-based soft X-ray microscopy (STXM/NEXAFS) was utilized to investigate and quantify extents of external and internal mixing. The later technique also provided advanced speciation of carbon bonding within individual particles, allowing to distinguish between organic and elemental carbon (soot), and inorganic components. Parameterized mixing state metrics were then correlated with online optical measurements recorded during each of the individual burning experiments. Results have shown significant differences in the elemental composition, with peat and grass being dominated by high content of organic material, while sage and pine are rich in inorganics. Additionally, the content of elemental carbon and inorganics per sample was found to increase bulk and individual particle chemical diversity, with further impact on the optical properties (i.e., mass absorption coefficient and absorption Angstrom exponent).