Towards Understanding of the Changes in Aerosol Sources, Trends, and Composition in the Southeastern and Continental United States (Invited Presentation) (Core Science Keynote)

Exposure to fine particulate matter pollution (PM_2.5) ranks among the top ten global health risks. Organic aerosols dominate ambient PM_2.5 and have important impacts on air quality, climate, and human health. A major fraction of organic aerosols are secondary organic aerosols (SOA), formed from atmospheric oxidation of a multitude of volatile organic compounds followed by gas-particle partitioning. With continued shifts in emissions, changes in climate, and increases in the frequency and intensity of wildfires, the sources, composition, and properties of aerosols are constantly evolving, posing a critical need to investigate these changes across scales to better understand their impacts on climate and human health in a changing world. Towards this end, we conducted multiple intensive field measurement campaigns in the greater Atlanta area throughout the last decade, levering advanced mass spectrometry capable of real-time bulk characterization of non-refractory submicron aerosols as well as speciation at the molecular level. New insights into how changing NO_x and SO₂ emissions impact biogenic SOA formation in the southeastern U.S. will be presented, as well as the prevalence of previously unrecognized contributions from aged biomass burning emissions to aerosols in the region. We also introduce the Atmospheric Science and Chemistry mEasurement NeTwork (ASCENT), a new comprehensive, high-time-resolution, long-term measurement network in the U.S. for the characterization of aerosol chemical composition and physical properties on spatiotemporal scales not previously possible. An overview of the measurement results from all 12 sites will be presented, highlighting similarities and differences in aerosol chemical composition and characteristics across urban, rural, and remote sites. We welcome collaborative opportunities leveraging the ASCENT infrastructure to advance our understanding of aerosol sources and characteristics and their impacts on air quality, climate, and health.