Abstract：
Ozone pollution presents a growing air quality threat in urban agglomerations in China. It remains challenge to distinguish the roles of emissions of precursors, chemical production and transportations in shaping the ground-level ozone trends, largely due to complicated interactions among these 3 major processes. This study elucidates the formation factors of ozone pollution and categorizes them into local emissions (anthropogenic and biogenic emissions), transport (precursor transport and direct transport from various regions), and meteorology. Particularly, we attribute meteorology, which affects biogenic emissions and chemical formation as well as transportation, to a perturbation term with fluctuating ranges. The Community Multiscale Air Quality (CMAQ) model was utilized to implement this framework, using the Pearl River Delta region as a case study, to simulate a severe ozone pollution episode in autumn 2019 that affected the entire country. Our findings demonstrate that the average impact of meteorological conditions changed consistently with the variation of ozone pollution levels, indicating that meteorological conditions can exert significant control over the degree of ozone pollution. As the maximum daily 8-hour average (MDA8) ozone concentrations increased from 20 % below to 30 % above the National Ambient Air Quality Standard II, contributions from emissions and precursor transport were enhanced. Concurrently, direct transport within Guangdong province rose from 13.8 % to 22.7 %, underscoring the importance of regional joint prevention and control measures under adverse weather conditions. Regarding biogenic emissions and precursor transport that cannot be directly controlled, we found that their contributions were generally greater in urban areas with high nitrogen oxides (NOx) levels, primarily due to the stronger atmospheric oxidation capacity facilitating ozone formation. Our results indicate that not only local anthropogenic emissions can be controlled in urban areas, but also the impacts of local biogenic emissions and precursor transport can be potentially regulated through reducing atmospheric oxidation capacity.
摘要：
臭氧污染对中国城市群的空气质量构成了日益严重的威胁。区分前体排放的作用仍然是挑战，化学生产和运输在塑造地面臭氧趋势方面，很大程度上是由于这三个主要过程之间复杂的相互作用。这项研究阐明了臭氧污染的形成因素，并将其分类为局部排放（人为和生物排放），运输(前体运输和来自不同地区的直接运输)，和气象学。特别是,我们归因于气象学，影响生物排放和化学形成以及运输，具有波动范围的扰动项。社区多尺度空气质量(CMAQ)模型被用来实现这个框架，以珠江三角洲地区为例，模拟2019年秋季影响整个国家的严重臭氧污染事件。我们的发现表明，气象条件的平均影响随着臭氧污染水平的变化而变化。表明气象条件可以对臭氧污染程度产生重大控制。由于最高每日8小时平均（MDA8）臭氧浓度从低于20％增加到高于国家环境空气质量标准II的30％，排放和前体运输的贡献有所增加。同时,广东省内的直接运输从13.8%上升到22.7%，强调在不利天气条件下采取区域联防联控措施的重要性。关于无法直接控制的生物排放和前体运输，我们发现，在氮氧化物(NOx)含量高的城市地区，它们的贡献通常更大，主要是由于更强的大气氧化能力促进臭氧形成。我们的结果表明，城市地区不仅可以控制当地的人为排放，但当地生物排放和前体运输的影响也可以通过降低大气氧化能力来调节。
