Characterization of Secondary Organic Aerosol Exposed to Acidic Sulfates: Chamber and Field Studies

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This project addresses the hypothesis that acidic sulfates have a significant impact on secondary organic aerosol (SOA) formation in the atmosphere via heterogeneous reactions that form nonvolatile products including organic sulfates (OS). The major goals are (1) to develop new analytical techniques to measure aerosol acidity and bulk phase products; (2) to elucidate the mechanism of SOA formation in multicomponent organic and inorganic mixtures; and (3) to evaluate the impact of acidic sulfates on SOA formation in ambient air. Organic compounds found in the atmosphere will be exposed to acidic sulfate solutions to imitate heterogeneous chemistry in acidic aerosols. Teflon chambers will be used to expose organic compounds to submicron acidic sulfate aerosols and to perform a wide range of SOA experiments. Various spectroscopic methods will be used to analyze the aerosol bulk phase products. A new technique will be developed to dynamically measure aerosol acidity using colorimetry coupled with reflectance UV-Visible spectrometry (C-RUV). The results obtained from the laboratory studies will then be applied to field data to evaluate the impact of acidic sulfate on organic carbon. A new predictive model will be developed to quantify the role of heterogeneous chemistry in SOA formation and growth.This study will help to explain how heterogeneous reactions change the chemical properties of atmospheric aqueous droplets, such as those in clouds, and how they affect aerosol optical properties. It also has implications for visibility and public health. Broader impacts also include support for a diverse group of graduate and undergraduate students. This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).