南京夏季大气臭氧光化学特征与敏感性分析

对流层臭氧（O₃）主要由氮氧化物（NO_x）和挥发性有机物（VOCs）经过一系列光化学反应生成，反应过程呈现复杂的非线性关系.为深入了解O₃的光化学特征及生成机制，利用2018年夏季大气O₃与VOCs的观测数据，结合大气零维框架模拟模型F0AM-MCM，研究O₃超标日和非O₃超标日的O₃光化学特征之间的差异性.观测结果表明，O₃超标日期间φ（O₃）和φ（TVOCs）的平均值分别为47.8×10^-9和49.0×10^-9，为非O₃超标日期间O₃（26×10^-9）和TVOCs（30×10^-9）体积分数的1.8倍和1.6倍.使用F0AM模型，借助EKMA曲线和RIR分析等识别O₃敏感性，发现南京市O₃超标日和非O₃超标日O₃的形成均主要受VOCs和NO_x的协同控制.F0AM-MCM模拟结果表明，在O₃超标日，·OH和HO₂的日平均混合比分别是非O₃超标日的1.3倍和1.8倍，表明O₃超标日期间具有更强的大气氧化能力，且·OH和HO₂的形成和损失速率也有明显的增加，表明自由基循环的增强.此外，O₃超标日的O₃生成速率明显高于非O₃超标日，从而导致了O₃超标日的O₃净生成速率明显高于非O₃超标日.以上发现提高了对南京夏季O₃超标日大气O₃光化学特征的认识.

Analysis of Photochemical Characteristics and Sensitivity of Atmospheric Ozone in Nanjing in Summer

Tropospheric ozone (O₃) is mainly produced through a series of photochemical reactions of nitrogen oxides (NO_x) and volatile organic compounds (VOCs). The reaction process presents complex non-linear relationships. In this work, datasets of atmospheric ozone and volatile organic compounds (VOCs) observed during the summer of 2018 in Nanjing were used. Combining with the framework for 0-D atmospheric model-master chemical mechanism (F0AM-MCM), the characteristics of photochemical reactions for ozone (O₃) formation in Nanjing during the O₃ episode days and non-episode days were investigated. The results showed that φ(O₃) and φ(TVOCs) in the O₃ episode days were 47.8×10^-9 and 49.0×10^-9, respectively, exceeding those in the non-episode days by factors of 1.8 and 1.6. Furthermore, F0AM, the empirical kinetic modeling approach (EKMA), and relative incremental reactivity (RIR) were utilized for the calculation of ozone chemical sensitivity. It was found that O₃ formation in Nanjing was attributed to both VOCs and NO_x limitation. In addition, the modeled ·OH and HO₂ concentrations in the O₃ episode days were 1.3 and 1.8 times higher than those in the non-episode days. The higher formation and loss rates of ·OH and HO₂ were also found during O₃ episode days. These findings reflected that the enhancements of atmospheric oxidation capacity resulted in increased production rates of O₃, providing an explanation for the enhancements of O₃ concentrations in Nanjing during the O₃ episode days. The findings also improved the understanding of the O₃ photochemical characteristics over Nanjing in the summer during the O₃ episode days.