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

摘要

The United Kingdom Chemistry and Aerosols (UKCA) chemistry–climate model is used to quantify the differences in chemical environment for surface O 3 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 O 3 photochemistry. We demonstrate that the model with the improved chemistry scheme captures the observed magnitudes and diurnal patterns of surface O 3 concentrations across these regions well. Simulated O 3 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 O 3 production rates in Guangzhou. NO x ? / ?VOC and H 2 O 2 ? / ? HNO 3 ratios indicate that O 3 production across all regions except Chongqing is VOC limited. We confirm this by constructing O 3 response surfaces for each region changing NO x and VOC emissions and further contrast the effectiveness of measures to reduce surface O 3 concentrations. In VOC-limited regions, reducing NO x emissions by 20?% leads to a substantial O 3 increase (11?%) in Shanghai. We find that reductions in NO x emissions alone of more than 70?% are required to decrease O 3 concentrations across all regions. Reductions in VOC emissions alone of 20?% produce the largest decrease ( ? 11?%) in O 3 levels in Shanghai and Guangzhou and the smallest decrease ( ? 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 NO x emission levels in these Chinese regions. Our work provides an assessment of the effectiveness of emission control strategies to mitigate surface O 3 pollution in these major industrial regions and emphasises that combined NO x and VOC emission controls play a pivotal role in effectively offsetting high O 3 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.