Preprints
https://doi.org/10.5194/egusphere-2024-341
https://doi.org/10.5194/egusphere-2024-341
30 Apr 2024
 | 30 Apr 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Opposite variations of peak and low ozone concentrations in eastern China: Positive effects of NOx control on ozone pollution

Zhuang Wang, Chune Shi, Hao Zhang, Xianguang Ji, Yizhi Zhu, Congzi Xia, Xiaoyun Sun, Xinfeng Lin, Shaowei Yan, Suyao Wang, Yuan Zhou, Chengzhi Xing, Yujia Chen, and Cheng Liu

Abstract. Due to the unbalanced emission reductions in ozone precursors in recent years, ozone trends and the causes of their variations in eastern China remain insufficiently understood. To explore the factors controlling ozone trends in eastern China, the long–term ozone precursors observation experiment was conducted. Combined with the satellite and surface measurements, the trend of low, typical and peak ozone concentrations in eastern China was evaluated in detail. Observation results show that the surface peak ozone concentrations significantly decreased (-0.5 % per year) while low ozone concentrations increased (0.3 % per year) in eastern China during May–September 2017–2022. The underlying cause of surface ozone trends in eastern China is anthropogenic emissions (~85 %), and the contribution of meteorological factors is not significant (~15 %). Ozone formation sensitivity is in VOC–limited regime or transition regime during periods (8:00–11:00) of sharp increases in ozone concentrations, and it is usually in NOx–limited regime when the ozone concentration reaches its peak (~14:00). Substantial reductions in nitrogen oxides (NOx) emissions have diametrically opposed effects on peak (decreasing) and low (increasing) ozone concentrations, and reducing volatile organic compounds (VOCs) concentrations is the key to reversing the current high ozone level situation in eastern China. In addition, there are obvious interannual variations of surface O3 formation sensitivity on spatial scales through long–term satellite observations, in which area proportion of VOC–limited regime is decreasing while the area proportion of NOx–limited regime is increasing. Our results highlight the positive impact of NOx reduction in controlling peak O3 levels, and regular changes in the ozone formation sensitivity throughout the day should be taken into account when formulating ozone control policies.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Zhuang Wang, Chune Shi, Hao Zhang, Xianguang Ji, Yizhi Zhu, Congzi Xia, Xiaoyun Sun, Xinfeng Lin, Shaowei Yan, Suyao Wang, Yuan Zhou, Chengzhi Xing, Yujia Chen, and Cheng Liu

Status: open (until 11 Jun 2024)

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Zhuang Wang, Chune Shi, Hao Zhang, Xianguang Ji, Yizhi Zhu, Congzi Xia, Xiaoyun Sun, Xinfeng Lin, Shaowei Yan, Suyao Wang, Yuan Zhou, Chengzhi Xing, Yujia Chen, and Cheng Liu
Zhuang Wang, Chune Shi, Hao Zhang, Xianguang Ji, Yizhi Zhu, Congzi Xia, Xiaoyun Sun, Xinfeng Lin, Shaowei Yan, Suyao Wang, Yuan Zhou, Chengzhi Xing, Yujia Chen, and Cheng Liu

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Short summary
This study attempts to explain the surface ozone background, typical, and peak trends in eastern China by combining a large amount of ground–based and satellite observations, and found substantial reductions in nitrogen oxides emissions have diametrically opposed effects on peak (decreasing) and low (increasing) ozone concentrations.