Impact of primary 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. In this study, we incorporate updated anthropogenic emission inventories for the Yangtze River Delta (YRD) region, featuring source-resolved OVOC profiles derived from measurements and literature, into the Community Multiscale Air Quality (CMAQ) model to improve regional OVOC simulations. The model reproduced the diurnal and seasonal variations of most observed OVOC concentrations, particularly carbonyl compounds, with moderate correlation coefficients of 0.40–0.79. Primary OVOCs originating from direct emissions accounted for 30 %–70 % of total OVOC concentrations, with higher contributions during colder months due to weaker atmospheric oxidation capacity and slight increases in anthropogenic OVOC emissions. In urban areas, hydroperoxyl radicals (HO2) served as a dominant oxidant driving NO-to-NO2 conversion, with more than 90 % of primary HO2 production attributed to OVOC photooxidation. Primary OVOCs alone accounted for approximately 20 %–50 % of primary HO2 production, with stronger influences in regions with elevated OVOC emissions. Sensitivity analysis further indicated that key primary OVOCs contributed to ozone formation at levels comparable to traditional VOC precursors. These findings underscore the critical yet often overlooked role of primary OVOCs in urban ozone formation, highlighting the need for more comprehensive assessments in regions like the YRD.