Autooxidation in the Condensed Phases - Implications to Cloudwater Chemistry and Indoor Occupational Health

Autooxidation has been known for a long time to cause a number of key oxidative processes in environmental and biological systems, such as lipid peroxidation and degradation of edible oil. Most of these processes occur in the condensed (i.e., liquid aqueous and organic) phases. A decade ago, autooxidation of volatile organic compounds in the ambient air was discovered. Since then, it has been shown to be responsible for the formation of highly oxygenated organic compounds in the atmosphere. While autooxidation occurring in the gas phase gathered a tremendous amount of attention from atmospheric chemists, studies of concerned-phase autooxidation under the context of atmospheric chemistry remained sparse. My research group has engaged in a series of experimental investigations to elucidate the mechanism and implications of condensed-phase autooxidation of atmospheric relevance. In the first project, we investigated the mechanism of aqueous-phase autooxidation relevant to cloudwater chemistry. Using a unique technique, iodometry-assisted liquid chromatography-mass spectrometry (LC-MS), we have monitored the formation of organic peroxides that served as indicators for the autooxidation mechanism. We found that aqueous-phase autooxidation is likely occurring in the ambient cloudwater. However, the choice of high organic concentrations and UV light with short wavelengths has likely been preventing detecting key peroxides in the laboratory. In the second project, we have investigated autooxidation occurring in glycol-based solvents. These solvents are commonly used in consumer products such as the stage fog, e-cigarettes, and personal care products. We found that oxidants in the indoor air likely initiate autooxidation in these solvents, forming harmful aldehydes and organic peroxides. Our observations have significant implications for indoor air quality and occupational health.