Heterogeneous and Photochemical Transformations on Aerosol Surfaces: Understanding the Link between Hydrogen Peroxide and Carbonates Using Carbon and Oxygen Triple Isotopes

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This project incorporates a novel approach for measuring in-situ formation of peroxide and carbonates using carbon and oxygen triple isotopes to help elucidate heterogeneous chemical transformations on aerosol surfaces. The ozone molecule is unique isotopically as it possesses the highest enrichment (70-120%) in the heavier isotopes of oxygen and serves as a natural tracer of chemical reactions involving ozone interaction. Since hydrogen peroxide is formed on aerosol surfaces, O-triple isotopic measurements of the newly formed peroxide on aerosol surfaces in the laboratory with ozone, water, and CaO indicate that the transfer of anomaly from ozone to carbonates proceeds via peroxide. This project employs both night and daytime aerosol sampling (12h sampling) of ambient air in La Jolla CA to look for day/night differences in 13C and oxygen triple isotopic composition (17O and 18O) of atmospheric carbonates and hydrogen peroxide in coarse and fine fractions of aerosols. The isotopic analyses in this project will help elucidate the molecular-level details of the mechanisms of heterogeneous reactions at aerosol surfaces.This effort will enhance our understanding of the radiative properties of aerosols, the role of oxygen isotopes in ice core data, impacts of aerosol transport to ecosystems, and health impacts of aerosols. The results will address the issue of thin films on aerosol surfaces while at the same time make progress in areas of importance to fundamental physical chemistry.