# Contrasting chemical environments in summertime for atmospheric ozone across major Chinese industrial regions: the effectiveness of emission control strategies

The United Kingdom Chemistry and Aerosols (UKCA) chemistry–climate model is used to quantify the differences in chemical environment for surface inline-formulaO3 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 inline-formulaO3 photochemistry. We demonstrate that the model with the improved chemistry scheme captures the observed magnitudes and diurnal patterns of surface inline-formulaO3 concentrations across these regions well. Simulated inline-formulaO3 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 inline-formulaO3 production rates in Guangzhou. inline-formulaNOxinline-formula $M7inlinescrollmathml/$ 8pt14ptsvg-formulamathimg36bd7baae116a5efc17e692d563c2b51 acp-21-10689-2021-ie00001.svg8pt14ptacp-21-10689-2021-ie00001.png  VOC and inline-formulaH2O2inline-formula $M9inlinescrollmathml/$ 8pt14ptsvg-formulamathimg880d1b22cfae9b4167ff115d05c6894c acp-21-10689-2021-ie00002.svg8pt14ptacp-21-10689-2021-ie00002.png inline-formulaHNO3 ratios indicate that inline-formulaO3 production across all regions except Chongqing is VOC limited. We confirm this by constructing inline-formulaO3 response surfaces for each region changing inline-formulaNOx and VOC emissions and further contrast the effectiveness of measures to reduce surface inline-formulaO3 concentrations. In VOC-limited regions, reducing inline-formulaNOx emissions by 20 % leads to a substantial inline-formulaO3 increase (11 %) in Shanghai. We find that reductions in inline-formulaNOx emissions alone of more than 70 % are required to decrease inline-formulaO3 concentrations across all regions. Reductions in VOC emissions alone of 20 % produce the largest decrease (inline-formula−11 %) in inline-formulaO3 levels in Shanghai and Guangzhou and the smallest decrease (inline-formula−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 inline-formulaNOx emission levels in these Chinese regions. Our work provides an assessment of the effectiveness of emission control strategies to mitigate surface inline-formulaO3 pollution in these major industrial regions and emphasises that combined inline-formulaNOx and VOC emission controls play a pivotal role in effectively offsetting high inline-formulaO3 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.

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Liu, Zhenze / Doherty, Ruth M. / Wild, Oliver / et al: Contrasting chemical environments in summertime for atmospheric ozone across major Chinese industrial regions: the effectiveness of emission control strategies. 2021. Copernicus Publications.

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