The critical role of oxygenated volatile organic compounds (OVOCs) in shaping photochemical O₃ chemistry and control strategy in a subtropical coastal environment

Abstract. Photochemical ozone (O₃) pollution remains a persistent environmental challenge, and growing evidence highlights the critical role of oxygenated volatile organic compounds (OVOCs) in photochemical processes. However, comprehensive and quantitative measurements of OVOCs remain limited. This study investigates the impact of OVOCs on O₃ formation mechanisms and radical budgets by intergrating high-resolution field measurements from a subtropical coastal region in South China with observation-based photochemical modeling. 63 OVOC species were quantified by a proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS), and account for 72 %–77 % of total VOC concentrations. The O₃-precusor relationship analysis revealed a transition regime for O₃ formation and high sensitivity to OVOCs. OVOC-related reactions, including OVOC photolysis, OVOC oxidation by OH and NO₃ radicals, contributed approximately 36 %–73 % to daytime production rates of HO₂ and RO₂ radicals. Model simulations without comprehensive consideration of OVOCs would significantly underestimate daytime production rates of O₃ and RO_x 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 improve OVOC-inclusive model frameworks. Such improvements are essential for accurately characterizing O₃-precursor relationships and for developing effective and sustainable strategies to mitigate regional O₃ pollution.