Ground ozone rise during the 2022 shanghai lockdown caused by the unfavorable emission reduction ratio of nitrogen oxides and volatile organic compounds

IF 4.2 2区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES
Qian Wang , Yuewu Li , Fangqian Zhong , Wanqi Wu , Hongliang Zhang , Rong Wang , Yusen Duan , Qingyan Fu , Qing Li , Lin Wang , Shaocai Yu , Abdewahid Mellouki , David C. Wong , Jianmin Chen
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Abstract

Ground-level ozone (O3) pollution has shifted from a scientific issue to a key focus of governmental action in China. In recent years, the concentration of NO2 in Shanghai has shown a decreasing trend of 3.7% annually, but ozone concentrations have exhibited significant interannual variability, particularly with a noticeable increase in 2022. This study focuses on investigating the mechanisms behind the increase in ozone concentration during the COVID-19 pandemic control period in 2022 in Shanghai, utilizing a combination of ground observation data, observation-based models, and chemical transport models for analysis. The results indicate that during the lockdown period, the mean values of daily maximum 8-h average O3 concentrations (MDA8 O3) in Shanghai increased by 17 μg/m³, with emission-related factors contributing 65.3%, primarily due to a blanket reduction in VOCs and NOx emissions during the lockdown, with a reduction ratio close to 1:1. However, this reduction ratio and intensity are not sufficiently reasonable to alleviate ozone pollution. Meanwhile, adverse meteorological conditions further exacerbated this effect, contributing 34.7%, with temperature rise having the greatest impact. Results from the chemical transport model show that with the total reduction in NOx and VOCs emissions unchanged, the greater the reduction in VOC emissions and the better the reduction effect on ozone pollution, reducing MDA8 O3 by approximately 10 μg/m³, especially for the control of reactive compounds such as alkenes, aromatics, and OVOCs. However, if the reduction ratio of NOx is greater than that of VOCs, ozone concentrations may not decrease but instead increase. This indicates that ozone concentration is influenced not only by the intensity of emissions reduction but also by the ratio of emissions reduction between NOx and VOCs. Our study emphasizes the critical role of carefully designed strategies, focusing on controlling the ratio of VOCs to NOx and increasing the intensity of VOCs reduction, to effectively alleviate ozone pollution in urban areas.
氮氧化物和挥发性有机化合物的不利减排比例导致 2022 年上海封锁期间地面臭氧上升
在中国,地面臭氧(O3)污染已从一个科学问题转变为政府行动的重点。近年来,上海的二氧化氮浓度呈现出每年下降 3.7% 的趋势,但臭氧浓度却呈现出明显的年际变化,尤其是在 2022 年出现了明显的上升。本研究结合地面观测数据、基于观测的模型和化学传输模型进行分析,重点研究 2022 年 COVID-19 大流行控制期间上海臭氧浓度上升的机理。结果表明,在封锁期间,上海臭氧日最大 8 小时平均浓度(MDA8 O3)均值增加了 17 μg/m³,其中排放相关因素占 65.3%,主要原因是封锁期间 VOCs 和 NOx 排放全面减少,减少比例接近 1:1。然而,这一减排比例和强度对于缓解臭氧污染来说还不够合理。同时,不利的气象条件进一步加剧了这一影响,占 34.7%,其中气温升高的影响最大。化学传输模型的结果表明,在氮氧化物和挥发性有机物排放总量削减比例不变的情况下,挥发性有机物排放削减比例越大,对臭氧污染的削减效果越好,可使 MDA8 O3 降低约 10 μg/m³ ,尤其是对烯烃、芳烃和 OVOCs 等活性化合物的控制效果更好。但是,如果氮氧化物的还原率大于挥发性有机化合物的还原率,臭氧浓度可能不会降低,反而会升高。这表明,臭氧浓度不仅受减排强度的影响,还受氮氧化物和挥发性有机化合物减排比例的影响。我们的研究强调了精心设计的战略对于有效缓解城市地区臭氧污染的关键作用,这些战略的重点是控制挥发性有机化合物与氮氧化物的比例以及提高挥发性有机化合物的减排强度。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Atmospheric Environment
Atmospheric Environment 环境科学-环境科学
CiteScore
9.40
自引率
8.00%
发文量
458
审稿时长
53 days
期刊介绍: Atmospheric Environment has an open access mirror journal Atmospheric Environment: X, sharing the same aims and scope, editorial team, submission system and rigorous peer review. Atmospheric Environment is the international journal for scientists in different disciplines related to atmospheric composition and its impacts. The journal publishes scientific articles with atmospheric relevance of emissions and depositions of gaseous and particulate compounds, chemical processes and physical effects in the atmosphere, as well as impacts of the changing atmospheric composition on human health, air quality, climate change, and ecosystems.
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