Atmospheric oxygenated organic compounds and their impacts on photochemical air pollution

Oxygenated organic compounds are key reactive pollutants that significant impact air quality and human health. They play critical roles in tropospheric photochemistry and oxidation capacity, profoundly influencing radical cycling and O₃ formation. Despite their importance, the precise quantification of these compounds remain a significant challenging. Here we present a comprehensive study of oxygenated volatile organic compounds (OVOCs) in coastal and urban air, employing a combination of real-time online mass spectrometry and offline sampling methods. The measurements revealed the substantial abundance of OVOCs and their significant contributions (~50%) to photochemical reactivity and O3 formation potential. Observation-based modeling analysis were performed to quantify the impacts of these reactive organic species on photochemistry and the formation of secondary pollutants. The results demonstrated that the OVOCs related reactions can contribute to 30-65% of peroxy radical formation and recycling, thereby enhancing daytime O3 formation. Model simulations without comprehensive consideration of OVOCs would significantly underestimate daytime production rates of O3 and ROx radicals by 41 %–48 %, and shift the diagnosis of O3 formation from a transition regime to a VOC-limited regime, leading to biased policy recommendations and potentially ineffective control strategies. These findings underscore the critical role of OVOCs in atmospheric photochemistry and highlight the urgent need for comprehensive OVOC quantification to accurately characterize O3-precursor relationships and for developing effective and sustainable strategies to mitigate regional photochemical air pollution.