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DES Centennial Celebration

Environmental Sciences Seminar

DATE/TIME:  Friday, May 6, 2022, 3:00 pm
PLACE: Remote Live

Jean C. Rivera Rios
Georgia Institute of Technology

Secondary Organic Aerosol Formation in Urban Environments: Lessons from the COVID-19 Pandemic and Ambient Perturbation Experiments in Atlanta

Gas-particle mixtures like smoke, sea spray and smog are collectively known as particulate matter (PM) or aerosols. Aerosols have diverse impacts on the environment, for example, they can transport nutrients on a global scale or serve as seeds for cloud formation. Depending on the type of aerosol, they can also have large impacts on human health, visibility and climate change. Secondary organic aerosols (SOA) is a major component of fine PM (PM2.5) and refers to aerosols formed from complex chemistry in the atmosphere, as opposed to primary aerosols which are directly emitted. The formation of SOA is due to the reactions of volatile organic compounds (VOCs) with gas-phase oxidants. The extent of these reactions and their products depend on the reaction partners available at a particular location. Urban environments have high population densities which leads to large emissions of pollutants like nitrogen oxides (NOx). NOx emissions can alter the oxidation of VOCs, contributing to the formation of pollutants like ozone and SOA. We evaluate the interplay between anthropogenic emissions and SOA formation in Atlanta, GA, using two methods. First, we performed ambient measurements of pollutants during the COVID-19 pandemic. The lockdowns during the early stages of the pandemic are a “natural experiment” that allows us to directly relate reductions in anthropogenic emissions to changes in SOA composition. The second approach is the use of ambient perturbation experiments. These experiments isolate oxidation conditions in the city at different times of day and relate them to the formation of secondary organic aerosols from a specific VOC. Together these results help us understand how specific types of SOA are formed and how their production can be mitigated effectively.