The surface of atmospheric particles is known to adsorb volatile and semi-volatile organic compounds during atmospheric transport, resulting in the formation of an organic coating around the aerosol particle. These organic coatings undergo oxidation in the presence of ozone and hydroxyl radicals, changing the chemical and physical properties of the aerosol. These interface reactions are important in understanding the energy and chemical balance of the atmosphere. Yet, little is known about the reaction of ozone and hydroxyl radicals with organic aerosol coatings. In this work we present a study from various oxidation reactions between a hydrocarbon-coated alumina surface and ozone or hydroxyl radicals. Heterogeneous oxidation was conducted in a state-of-the-art chamber that allows for the in-situ observation of the reaction. The chamber’s two-dimensional spectroscopic set-up allows for the use of UV-vis spectroscopy and infrared vibrational spectroscopy to investigate the chemical kinetics of the oxidation process. Ex-situ analysis was also conducted to determine the products of the reaction. Finally, quantum chemical calculations of the adsorbed reactants were also performed to determine the configuration of adsorbed species. Our results suggest that the atmospheric oxidation of chemisorbed organic compounds and ozone primarily result in surface bound organic carbonyl compounds while the reaction with hydroxyl radicals leads to the formation of alcohols.

Heterogeneous oxidation of aerosol organic coatings in the presence of O3 and OH radicals

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