AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Physical, Chemical and Optical Properties of Wildfire Aerosols
SWARUP CHINA, Matthew Brege, Simeon Schum, Daniel Veghte, Kaitlyn J. Suski, Gourihar Kulkarni, ManishKumar Shrivastava, Lynn Mazzoleni, Alla Zelenyuk, Pacific Northwest National Laboratory
Abstract Number: 735 Working Group: Biomass Combustion: Emissions, Chemistry, Air Quality, Climate, and Human Health
Abstract Wildfire is one of the major sources of carbonaceous aerosols in the atmosphere and significantly impacts the radiative forcing of climate at regional and global scales. The radiative forcing of biomass burning aerosol is highly uncertain partly due to the balance between the positive forcing due to absorbing aerosol and negative forcing by weakly absorbing or non-absorbing aerosol particles. Characterization of the physicochemical and optical properties of individual particles and molecular characterization of bulk aerosol are crucial for predictive understanding of radiative forcing of biomass burning particles. Optical properties of biomass burning particles, especially for tar balls, are highly uncertain because of the current knowledge gap about the imaginary part of the complex index of refraction of tar balls. Here, we investigated the physicochemical and optical properties of individual particles from a wildfire influenced plume with high mass loadings. Physicochemical properties of individual particles were characterized using micro-spectroscopy and single particle mass spectrometry techniques and molecular characterization was performed using advanced mass spectrometry techniques. The optical properties of tar balls were derived from the quantitative analysis of the electron energy-loss spectra acquired over individual particles using scanning transmission electron microscopy. A single particle mass spectrometer, miniSPLAT was used to characterize in real-time the size, shape, density, composition, and volatility of individual biomass burning particles. Results indicate that the vast majority of biomass burning particles were spherical tar balls with densities of 1.3 - 1.45 g/cm3, depending on particle size and composition. The characterized particles were nearly non-volatile and retained over 90% of their volume after 24 hours of evaporation at low relative humidity (<5% RH). We will present an overview of the physical, chemical and optical properties of wildfire aerosols. The results from this study should improve predictions of the radiative impact of wildfire aerosols on regional and global climate.