题名：Attributing Increases in Ozone to Accelerated Oxidation of Volatile Organic Compounds at Reduced Nitrogen Oxides Concentrations

来源：PNAS Nexus

发表年代：2022

作者： Zekun Zhang, Jiakui Jiang, Bingqing Lu, Xue Meng, Hartmut Herrmann, Jianmin Chen, Xiang Li*

Abstract：Surface ozone (O₃) is an important secondary pollutant affecting climate change and air quality in the atmosphere. Observations during the COVID-19 lockdown in urban China show that the co-abatement of nitrogen oxides (NOₓ) and volatile organic compounds (VOCs) caused winter ground-level O₃ increases, but the chemical mechanisms involved are unclear. Here we report field observations in the Shanghai lockdown that reveals increasing photochemical formation of O₃ from VOC oxidation with decreasing NOₓ. Analyses of the VOC profiles and NO/NO₂ indicate that the O₃ increases by the NOₓ reduction counteracted the O₃ decreases through the VOC emission reduction in the VOC-limited region, and this may have been the main mechanism for this net O₃ increase. The mechanism may have involved accelerated OH-HO₂-RO₂ radical cycling. The NOₓ reductions for increasing O₃ production could explain why O₃ increased from 2014 to 2020 in response to NOₓ emission reduction even as VOC emissions have essentially remained unchanged. Model simulations suggest that aggressive VOC abatement, particularly for alkenes and aromatics, should help reverse the long-term O₃ increase under current NOₓ abatement conditions.