Dynamic Oxidative Potential of Organic Aerosol from Heated Cooking Oil

Cooking emissions contribute significantly to organic aerosol in urban areas, but the evolution of physicochemical properties and health impacts upon atmospheric aging remain poorly understood. In this study, detailed chemical composition and oxidative potential (OP) of primary organic aerosol (POA) and secondary organic aerosol (SOA) from heated cooking oils (canola, olive, peanut) were characterized. Results from acellular oxidative potential measurements indicate an enhanced OP in photochemically aged cooking SOA compared to that in POA, which is accompanied by increasing abundance of reactive oxygen species (ROS) measured using electron paramagnetic resonance (EPR) spectroscopy. In SOA from heated canola oil, enhanced total ROS production (by a factor of 26) coincides with the increased particle-phase peroxide content (from 15 to 26%) across six different photooxidation conditions (up to 2 days of atmospheric aging equivalent). Positive correlations were found among total ROS abundance, peroxide content, and average carbon oxidation state of canola oil SOA along with aging. Photooxidation of representative volatile compounds from heated cooking oils shows that unsaturated aldehydes are the dominant contributors to peroxides in cooking oil SOA during atmospheric aging, and the degree of unsaturation in the aldehyde precursor is linked with the total ROS/peroxide content in SOA. The abundant OH radicals suggest that peroxides are the major radical source in aged cooking SOA, likely initiated by the homolytic cleavage of the oxygen-oxygen single bond. Our study bridges the chemical composition and OP of cooking aerosol upon atmospheric aging, shedding light on the evolution of cooking emissions and their dynamic toxicity in the atmosphere.