Comparative analysis of tropospheric ozone sources in typical regions of China using optimized emission inventories and numerical simulation

In recent years, tropospheric ozone (O 3 ) pollution has become an increasingly serious issue in China. Elevated concentrations persist during the summer, not only in the densely populated eastern regions but also in the sparsely populated western regions. In this study, a rapid emission optimizing method was developed and applied using the Regional Atmospheric Modeling System-Community Multi Scale Air Quality (RAMS-CMAQ) modeling system. Satellite observations were then integrated to optimize nitrogen oxide (NO x ) and volatile organic compound (VOC) emissions over the Qinghai and Beijing-Tianjin-Hebei (BTH) regions. Based on the improved emission inventory, a numerical source apportionment model was employed to estimate the source contributions of tropospheric O 3 in both regions during June 2024. Results showed that O 3 levels in the BTH region were primarily influenced by industrial and traffic emissions, as well as anthropogenic emissions transported from neighboring cities. In contrast, anthropogenic contributions in Qinghai were significantly lower, while natural sources and long-range transport played a more dominant role, underscoring their critical importance in this region. Because the high O 3 burden in Qinghai results from multiple interacting factors, pollution control is more challenging, and thus requires a more refined and comprehensive governance strategy. • 1.Optimized emissions significantly improved O 3 simulation accuracy, especially peak values. • 2.BTH O 3 dominated by industry and traffic; natural sources exceed 20% in Qinghai. • 3.Regional transport contributes 25% to Qinghai O 3 , requiring refined control.