Seminar

Abstract

Biomass burning (BB) is a major source of pollutants that impact local, regional, and global air quality, and public health. Work in our lab is focused on emissions from African biomass fuels - a hotspot source region of carbonaceous aerosols on a global scale. Recently we investigated the relationship between morphology (fractal dimensions) and modified combustion efficiency (MCE); determined fractal dimensions from TEM images; measured emission factors of pollutants from six different sub-Saharan African biomass fuels combusted under a wide range of burning conditions (MCE’s). Our most recent work determined the influence of combustion condition and fuel type on the hygroscopicity parameter of BB aerosols measured using the enhancement in light extinction coefficient (f(RH)) using cavity ring-down spectroscopy (CRDS) and a cloud condensation nuclei counter (CCNC). Ongoing studies in our laboratory focus on investigating how the molecular-level composition of smoldering-dominated organic-rich solid African biomass burning aerosols change as a function of aging conditions (i.e., fresh versus dark/photochemical/cloud water aging) and how these aerosol optical properties (mass scattering, absorption, and extinction cross-sections, absorption/scattering Ångström exponents, and the single scattering albedo) change because of any potential molecular-level chemical changes. We plan to analyze filter samples with a platform that consists of ultra-performance liquid chromatography coupled in-line to a diode array detector and a high-resolution quadrupole time-of-flight mass spectrometer, equipped with an electrospray ionization source operated in both positive and negative ion modes. The simultaneous absorption and mass spectral optimized chromatographic analysis of solvent extracts is expected to reveal individual BrC constituents and their key chemical characteristics. The evaluation of the constituents’ atmospheric relevance is based on analysis of filter samples collected in the lab and two distinct locations in Africa (Botswana) during the dry-winter fire season in 2022, followed by mass closure of the main chromophores. This study will add to the growing knowledge in African fuel sources and their varied impact on climate and air quality.

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Dr. Solomon Bililign is a professor in the Physics Department at North Carolina Agricultural and Technical State University (NCA&T). He received his BS and MS degrees in Physics from Addis Ababa University, and his PhD in Physics from the University of Utah. After completing his postdoctoral work in the Chemistry department of the University of Utah, he joined the faculty of NCAT in 1993. He received the Presidential Award for Excellence in Science, Mathematics, and Engineering Mentoring in 2010, as well as several other awards from NCA&T for excellence in teaching and research. He served as the director of the NOAA-funded Interdisciplinary Scientific Environmental Technology (ISET) Cooperative Science Center.