Significant influence of oxygenated volatile organic compounds on atmospheric chemistry analysis: A case study in a typical industrial city in China

Abstract. Oxygenated volatile organic compounds (OVOCs), key components of volatile organic compounds (VOCs), are either directly emitted or secondary generated via photochemical processes, and play a crucial role in tropospheric photochemistry and act as important ozone (O₃) precursors. However, due to measurement limitations, the influence of OVOCs on O₃ formation has often been underestimated. In this study, 74 VOCs (including 18 OVOCs) were measured at five representative stations in Zibo, an industrial city in the North China Plain. The VOCs level in Zibo (44.6±20.9 ppb) is in the upper-middle range compared with previous studies, with OVOCs contributing 30.0 %~37.8 % to the total VOCs concentration. The overall O₃ formation potential in Zibo is 410.4±197.2 µg m^-3, with OVOCs being the dominant contributor (31.5 %~55.9 %). An observation-based model (OBM) was used to access the contributions of chemical production (R_NetProd) and emissions/transport (R_Emis&Trans) to individual OVOC. Daytime R_NetProd is the highest at the urban site (5.9 ppb h^-1), while nighttime R_Emis&Trans is most significantly negative at the industrial site (0.76 ppb h^-1). Simulations without OVOCs constraint overestimates OVOCs (42.1 %~126.5 %) and key free radicals (e.g., HO₂ (5.3 %~20.4 %) and RO₂ (6.6 %~35.1 %)), leading to a 1.8 %~11.9 % overestimation of O₃. This overestimation causes an underestimation of OH (1.8 %~20.9 %) and atmospheric oxidizing capacity (3.5 %~12.5 %). These findings emphasize the importance of comprehensive OVOCs measurements to constrain numerical models, especially in regions with dense anthropogenic emissions, to better reproduce atmospheric photochemistry, and to formulate more effective air pollution control strategies.