Photooxidation of Oxygenated Volatile Organic Compounds as a Major Source of Hydroperoxyl Radicals Driving Ozone Formation in the Yangtze River Delta Region

Oxygenated volatile organic compounds (OVOCs) significantly contribute to the radical formation in the troposphere, enhancing atmospheric oxidation capacity and driving secondary pollutant production. However, uncertainties in OVOC emissions hinder accurate assessments of their regional impacts. This study updates OVOC emission profiles for the Yangtze River Delta (YRD) region and integrates them into the Community Multiscale Air Quality (CMAQ) model to refine OVOC estimations. The updated model effectively captures the diurnal variations of most OVOCs, significantly reducing biases compared to simulations based on previous inventories. OVOCs, particularly formaldehyde (HCHO), are key precursors of hydroperoxyl radicals (HO₂), which play a dominant role in ozone production across the YRD. Anthropogenic emissions, primarily from industrial activities and vehicular sources, account for 40−60% of total OVOCs. Sensitivity simulations reveal that reducing emissions of reactive OVOCs, such as HCHO and glyoxal, effectively lowers regional ozone levels. These findings underscore the pivotal role of OVOCs in radical chemistry and ozone formation, providing insights for mitigating ozone pollution in rapidly urbanizing regions like the YRD.