A comprehensive analysis of O3 variation and source contributions of VOCs-oriented to O3 pollution episodes over Jinan city, China

Although severe ozone (O₃) pollution has been frequently observed during summer over Jinan city in northern China, which underscores the necessity of mitigating O₃ pollution, the key formation processes and prominent sources of O₃ pollution episode remain poorly characterized. In this study, the Weather Research and Forecasting (WRF)-Community Multiscale Air Quality (CMAQ) modeling system was employed to investigate the formation mechanism of O₃ pollution during summer in Jinan. In addition, the Integrated Source Apportionment Method (ISAM) was subsequently applied to determine the major VOCs contributors to elevated O₃ levels. During O₃ pollution episodes, increased O₃ concentrations generated by gas-chemistry at high altitudes were transported to the ground through vertical transport, exacerbating surface-level O₃ pollution caused by photochemical reactions during daytime. The declined height of the planetary boundary layer (PBLH) and vertical mixing, which form O₃-rich residual layers, were identified as the key drivers of the O₃ accumulation and enhancement near the surface during nighttime. Furthermore, ISAM results indicate that terminal olefin carbon bonds (OLE), internal olefin carbon bonds (IOLE), and ethene (ETH) playing essential roles in O₃ formation, collectively contributing up to 60 %. This implicates great importance of vehicle exhaust and the use of liquefied petroleum gas (LPG) and natural gas (NG) over Jinan city. Our findings offer possible explanations for O₃ pollution episode and provide a quantitative understanding of O₃ source apportionment, guiding the control strategy of VOCs-oriented on O₃ mitigation.