Abstract
Tropospheric ozone (O(3)) concentration is increasing in China along with dramatic changes in precursor emissions and meteorological conditions, adversely affecting human health and ecosystems. O(3) is formed from the complex nonlinear photochemical reactions from nitrogen oxides (NO (x) = NO + NO(2)) and volatile organic compounds (VOCs). Although the mechanism of O(3) formation is rather clear, describing and analyzing its changes and formation potential at fine spatial and temporal resolution is still a challenge today. In this study, we briefly summarized and evaluated different approaches that indicate O(3) formation regimes. We identify that atmospheric oxidation capacity (AOC) is a better indicator of photochemical reactions leading to the formation of O(3) and other secondary pollutants. Results show that AOC has a prominent positive relationship to O(3) in the major city clusters in China, with a goodness of fit (R (2)) up to 0.6. This outcome provides a novel perspective in characterizing O(3) formation and has significant implications for formulating control strategies of secondary pollutants.