Seminar

Abstract

Secondary organic aerosols (SOA), formed from multiphase oxidation of biogenic and anthropogenic precursors, are a major component of submicron aerosols, impacting air quality and climate. Although traditionally SOA has been thought to be purely scattering in nature, field and laboratory measurements have observed SOA with strong absorption at near UV and visible wavelengths (with a stronger absorption in the near UV compared to the visible). Specific functional groups and chemical moieties have been identified as the source of chromophores in primary OA and SOA. Here I present a summary of our work aimed at understanding chemical and microphysical properties of SOA that contribute to their light absorption properties and direct impacts on the Earth's radiative budget. The SOA were formed from hydroxyl or nitrate radical oxidation of pure and mixed hydrocarbons (that are typical of biogenic, urban, and biomass burning emissions) under variable oxidation conditions (relative humidity, NO_x, or NH₃ levels). I present results from online and offline techniques to gain insight into the drivers of SOA optical properties in these different systems.

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Dr. Roya Bahreini is a Professor of Atmospheric Science and the Vice Chair in the Department of Environmental Sciences at University of California, Riverside. She specializes in airborne, ground-based, and laboratory measurements of aerosol composition and microphysical properties to understand aerosol sources and formation process, influence on air quality, and direct- and indirect-effects on climate. Dr. Bahreini received her B.S. in Chemical Engineering from University of Maryland, College Park (1999), and M.S. (2003) and Ph.D. (2005) degrees in Environmental Science and Engineering from California Institute of Technology. Before joining UC Riverside, she was a CIRES Visiting Postdoctoral Fellow at University of Colorado Boulder (2005-2007), a Research Scientist at CIRES and NOAA ESRL CSD (2007-2012), and University of Denver (2012). She is a recipient of the National Science Foundation CAREER award, the Thomson Reuters Highly Cited Researchers award (2014), as well as The World's Most Influential Scientific Minds award (2014). In 2019-2020, she served on the Owens Lake Scientific Advisory Panel by the National Academies of Sciences, Engineering, and Medicine. She is currently a Board Member of the American Association for Aerosol Research.