Aggravating O3 pollution due to NOx emission control in eastern China

Nan Wang; Xiaopu Lyu; Xuejiao Deng; Xin Huang; Fei Jiang; Aijun Ding

doi:10.1016/j.scitotenv.2019.04.388

Aggravating O₃ pollution due to NO_x emission control in eastern China

Sci Total Environ. 2019 Aug 10:677:732-744. doi: 10.1016/j.scitotenv.2019.04.388. Epub 2019 Apr 28.

Authors

Nan Wang¹, Xiaopu Lyu², Xuejiao Deng³, Xin Huang⁴, Fei Jiang⁵, Aijun Ding⁶

Affiliations

¹ Joint International Research Laboratory of Atmospheric and Earth System Sciences, School of Atmospheric Sciences, Nanjing University, Nanjing, China; Jiangsu Provincial Collaborative Innovation Center for Climate Change, Nanjing, China; Institute of Tropical and Marine Meteorology, China Meteorological Administration, Guangzhou, China.
² Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hong Kong.
³ Institute of Tropical and Marine Meteorology, China Meteorological Administration, Guangzhou, China.
⁴ Joint International Research Laboratory of Atmospheric and Earth System Sciences, School of Atmospheric Sciences, Nanjing University, Nanjing, China; Jiangsu Provincial Collaborative Innovation Center for Climate Change, Nanjing, China. Electronic address: xinhuang@nju.edu.cn.
⁵ Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, International Institute for Earth System Science, Nanjing University, Nanjing 210023, China.
⁶ Joint International Research Laboratory of Atmospheric and Earth System Sciences, School of Atmospheric Sciences, Nanjing University, Nanjing, China; Jiangsu Provincial Collaborative Innovation Center for Climate Change, Nanjing, China.

PMID: 31075619
DOI: 10.1016/j.scitotenv.2019.04.388

Abstract

During the past five years, China has witnessed a rapid drop of nitrogen oxides (NO_x) owing to the wildly-applied rigorous emission control strategies across the country. However, ozone (O₃) pollution was found to steadily deteriorate in most part of eastern China, especially in developed regions such as Jing-Jin-Ji (JJJ), Yangtze River Delta region (YRD) and Pearl River Delta region (PRD). To shed more light on current O₃ pollution and its responses to precursor emissions, we integrate satellite retrievals, ground-based measurements together with regional numerical simulation in this study. It is indicated by multiple sets of observational data that NO_x in eastern China has declined more than 25% from 2012 to 2016. Based on chemical transport modeling, we find that O₃ formation in eastern China has changed from volatile organic compounds (VOCs) sensitive regime to the mixed sensitive regime due to NO_x reductions, substantially contributing to the recent increasing trend in urban O₃. In addition, such transitions tend to bring about an ~1-1.5 h earlier peak of net O₃ formation rate. We further studied the O₃ precursors relationships by conducting tens of sensitivity simulations to explore potential ways for effective O₃ mitigation. It is suggested that the past control measures that only focused on NO_x may not work or even aggravate O₃ pollution in the city clusters. In practice, O₃ pollution in the three regions is expected to be effectively mitigated only when the reduction ratio of VOCs/NO_x is greater than 2:1, indicating VOCs-targeted control is a more practical and feasible way.

Keywords: Emission sensitivity; Ozone pollution; Policy application; WRF-CMAQ.