Impact of Primarily Emitted Oxygenated Volatile Organic Compounds on Ozone Formation in the Yangtze River Delta Region

Abstract. Oxygenated volatile organic compounds (OVOCs) play a crucial role in tropospheric radical chemistry, which in turn enhances atmospheric oxidation capacity and drives the formation of secondary pollutants. However, large uncertainties in their emissions pose challenges to accurately assessing their impacts on regional air quality. This study incorporates updated anthropogenic emission inventories, featuring source-resolved OVOC profiles derived from measurements and literature, into the Community Multiscale Air Quality (CMAQ) model to improve OVOC simulations over the Yangtze River Delta (YRD) region. The model well captured the diurnal and seasonal variations of most OVOCs, especially carbonyls. Primary emissions accounted for 30−70 % of total OVOC concentrations, with higher contributions during colder months due to weaker atmospheric oxidation capacity. Hydroperoxyl radicals (HO₂), the primary oxidant driving NO-to-NO₂ conversion in urban areas, were substantially produced through OVOC photooxidation. Of the HO₂ produced by this process, approximately 15−40 % originated from directly emitted OVOCs rather than from secondary OVOCs formed via VOC oxidation. Sensitivity analysis further indicated that key emitted OVOCs contributed to ozone formation at levels comparable to traditional VOC precursors. These findings underscore the critical yet often overlooked role of primary OVOC emissions in urban ozone formation, highlighting the need for more comprehensive assessments in regions like the YRD.