ORIGINAL RESEARCH article
Front. Environ. Sci.
Sec. Atmosphere and Climate
Dominant Role of Humidity Thresholds in Driving Seasonal Ozone Production Regimes in Urban Guiyang, Yunnan-Guizhou Plateau
Provisionally accepted
Yang Yuan1
Hong Hu1Yonghong Wang2*
Hao Zhang3
Yao Dan4Wei Huang5Rong Li2Keyong Zhu1Ya Xiong1Li Lai1Dengmei Chen1Peisong Feng1- 1Guizhou Academy of Environmental Science and Design, Guiyang, China
- 2Guizhou Provincial Ecological and Environmental Monitoring Center, Guiyang, China
- 3Shandong Second Medical University, Weifang, China
- 4Henan Normal University, Xinxiang, China
- 5Xi'an University of Architecture and Technology, Xi'An, China
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Ground-level ozone (O₃) pollution has emerged as a significant environmental challenge in Guiyang, a plateau city in southwestern China, despite its reputation for high ecological quality. This study investigates the seasonality of O₃ production rates and sensitivities through comprehensive in-situ measurements of O₃ and its precursors from August 2022 to August 2024. Our results reveal that O₃ concentrations in Guiyang peak during spring (35.0±17.0 ppb) and autumn (28.1±17.0 ppb). This contrasts sharply with the summer-dominant patterns observed in the North China Plain and Yangtze River Delta regions. This anomaly is attributed to the interplay of meteorological factors, such as high humidity and monsoon rains in summer, which suppress O₃ accumulation. Random forest modeling integrated with SHapley Additive exPlanations (SHAP) identify relative humidity (RH) as the dominant factor influencing O₃ variability, exhibiting threshold-dependent suppression effects (RH > 80% in spring/summer; >75% in autumn/winter). Chemical budget analyses highlight that O₃ production is primarily driven by RO₂+NO reactions (52.4-56.8%) in non-winter seasons, shifting to HO₂+NO (54.6%) in winter, while O₃ destruction is dominated by photolysis (46.8-53.3%). Regional transport plays a minor role, with photochemical production dominating daytime accumulation versus physical advection prevailing at night. Sensitivity simulations indicate a NOₓ-limited regime for O₃ control in spring, summer, and autumn, advocating for targeted NOₓ reductions, whereas a transitional (VOCs-NOₓ co-limited) regime in winter necessitate coordinated control of both precursors. These findings underscore the need for seasonally tailored emission control strategies to mitigate O₃ pollution in plateau regions, emphasizing the interplay of meteorology, chemistry, and precursor emissions.
Keywords: Ozone production, relative humidity, seasonal variability, VOC-NOₓ sensitivity, Yunnan-Guizhou Plateau
Received: 20 Jan 2026; Accepted: 09 Feb 2026.
Copyright: © 2026 Yuan, Hu, Wang, Zhang, Dan, Huang, Li, Zhu, Xiong, Lai, Chen and Feng. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Yonghong Wang
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