Atmospheric aqueous phases such as clouds, fog drops, and aerosol liquid water (ALW) are important sites for the transformation of organic compounds. Aqueous oxidants that play a major role include hydroxyl radical (●OH), triplet excited organic states (3C* or triplets), and singlet molecular oxygen (1O2*). Singlet oxygen concentrations are consistently higher than these other two oxidants, showing its potential to be an important aqueous oxidant. Singlet oxygen, however, is a relatively selective oxidant, with the fastest rate constants toward electron-rich compounds such as furans, which are emitted from biomass burning (BB) and other sources. While singlet oxygen reacts quickly with some furans, most past studies have used organic solvents and thus there are few aqueous rate constants. To address this, we are measuring second-order rate constants for 14 furans in water (pH 5 and 20°C). Using our rate constant data, we will construct a quantitative-structure activity relationship to help predict rate constants of singlet oxygen with a wide range of furans of varying substitution. We will also measure the impact of inorganic salts, galactose (a BB sugar), and trace metals, which are common components in ALW. Lastly, we will combine our data to assess the significance of singlet oxygen as an aqueous-phase oxidant of furans compared to ●OH and triplets.

Oxidation of furans by singlet oxygen (1O2*) in clouds, fog drops, and aerosol liquid water

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