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<p>The United Kingdom Chemistry and Aerosols (UKCA) chemistry–climate model is used to quantify the differences in chemical environment for surface <span class="inline-formula">O₃</span> for six major industrial regions across China in summer 2016. We first enhance the UKCA gas-phase chemistry scheme by incorporating reactive volatile organic compound (VOC) tracers that are necessary to represent urban and regional-scale <span class="inline-formula">O₃</span> photochemistry. We demonstrate that the model with the improved chemistry scheme captures the observed magnitudes and diurnal patterns of surface <span class="inline-formula">O₃</span> concentrations across these regions well. Simulated <span class="inline-formula">O₃</span> concentrations are highest in Beijing and Shijiazhuang on the North China Plain and in Chongqing, lower in Shanghai and Nanjing in the Yangtze River Delta, and lowest in Guangzhou in the Pearl River Delta despite the highest daytime <span class="inline-formula">O₃</span> production rates in Guangzhou. <span class="inline-formula">NO_<i>x</i></span> <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="36bd7baae116a5efc17e692d563c2b51"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10689-2021-ie00001.svg" width="8pt" height="14pt" src="acp-21-10689-2021-ie00001.png"/></svg:svg></span></span> VOC and <span class="inline-formula">H₂O₂</span> <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="880d1b22cfae9b4167ff115d05c6894c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10689-2021-ie00002.svg" width="8pt" height="14pt" src="acp-21-10689-2021-ie00002.png"/></svg:svg></span></span> <span class="inline-formula">HNO₃</span> ratios indicate that <span class="inline-formula">O₃</span> production across all regions except Chongqing is VOC limited. We confirm this by constructing <span class="inline-formula">O₃</span> response surfaces for each region changing <span class="inline-formula">NO_<i>x</i></span> and VOC emissions and further contrast the effectiveness of measures to reduce surface <span class="inline-formula">O₃</span> concentrations. In VOC-limited regions, reducing <span class="inline-formula">NO_<i>x</i></span> emissions by 20 % leads to a substantial <span class="inline-formula">O₃</span> increase (11 %) in Shanghai. We find that reductions in <span class="inline-formula">NO_<i>x</i></span> emissions alone of more than 70 % are required to decrease <span class="inline-formula">O₃</span> concentrations across all regions. Reductions in VOC emissions alone of 20 % produce the largest decrease (<span class="inline-formula">−</span>11 %) in <span class="inline-formula">O₃</span> levels in Shanghai and Guangzhou and the smallest decrease (<span class="inline-formula">−</span>1 %) in Chongqing. These responses are substantially different from those currently found in highly populated regions in other parts of the world, likely due to higher <span class="inline-formula">NO_<i>x</i></span> emission levels in these Chinese regions. Our work provides an assessment of the effectiveness of emission control strategies to mitigate surface <span class="inline-formula">O₃</span> pollution in these major industrial regions and emphasises that combined <span class="inline-formula">NO_<i>x</i></span> and VOC emission controls play a pivotal role in effectively offsetting high <span class="inline-formula">O₃</span> levels. It also demonstrates new capabilities in capturing regional air pollution that will permit this model to be used for future studies of regional air-quality–climate interactions.</p>