Spectro-microscopy of Ambient Aerosol Particles: Observational Constraints on Mixing State Parameterization

Friday, 19 December 2014
Rachel E OBrien1, Bingbing Wang2, Alexander Laskin2, Matthew West3, Nicole S Riemer4, Mary Kathleen Gilles1 and Ryan Moffet5, (1)Lawrence Berkeley National Lab, Berkeley, CA, United States, (2)Pacific Northwest National Laboratory, Richland, WA, United States, (3)University of Illinois at Urbana Champaign, Mechanical Science and Engineering, Urbana, IL, United States, (4)University of Illinois, Urbana, IL, United States, (5)University of the Pacific, Stockton, CA, United States
Individual aerosol particles are often mixtures of multiple components such as inorganic salts, soot or elemental carbon, and organic molecules. The amounts of the different components in each particle and the particle morphologies will impact the CCN activity and the radiative properties of the aerosol population. A recent parameterization of the mixing state developed by Nicole Riemer and Matthew West provides a clear transition between ambient measurements of aerosol components and particle mixing states employed in climate models. Single particle spectro-microscopy techniques including scanning transmission x-ray microscopy/near-edge x-ray absorption fine structure spectroscopy (STXM/NEXAFS) and computer controlled scanning electron microscopy/energy dispersive x-ray spectroscopy (CCSEM/EDX) are used to measure the composition of aerosol particles from the CARES campaign at both T0 and T1. Here, we present results from the application of the per particle composition to a parameterization of the mixing state and provide constraints on the mixing state of ambient aerosol particles. The two microscopy techniques yield complementary information on the mixing state of the aerosol populations; STXM/NEXAFS provides information on the mixing state of the organic fraction while CCSEM/EDX provides information on the inorganic fraction.