Evolving Urban–Rural Disparities in Ozone Sensitivity Reveal Shifting Emission Contributions in Different Regions in China

Surface ozone (O 3 ) pollution has significant health and environmental impacts. Clarifying the distribution of urban–rural disparities in ozone (URD-O 3 ) is crucial for targeted O 3 management. However, the evolution patterns and the driving factors of URD-O 3 remain unclear. This study analyzed the spatiotemporal evolution of O 3, emissions and meteorology, in Beijing–Tianjin–Hebei (BTH) and Yangtze River Delta (YRD) from 2013 to 2020 in China, and quantitatively evaluated their relative contributions to URD-O 3 . Results show a clear divergence in URD-O 3 around 2017. Before 2017, urban O 3 in BTH was lower than rural levels but exceeded rural levels subsequently, peaking at 1.18 μg/m 3 in 2020. In contrast, YRD consistently showed higher urban O 3, where URD-O 3 increased by 58.9% from 2013 to 2017 and stabilized thereafter. Moreover, the relative contributions of emissions in two regions are opposite. In BTH, the contribution of emissions to URD-O 3 decreased from 40.1% to 20.2%, while it increased from 33.7% to 45.9% in YRD from 2013 to 2020. This result was attributed to the changes in O 3 sensitivity, the URD-O 3 sensitivity continuously narrowed in BTH, but widened in the YRD, altering the impact of emissions on O 3 formation. This study highlights the importance of O 3 sensitivity in O 3 targeted governance.