Spatial-temporal characteristics and meteorological drivers of ground-level ozone pollution in a Valley Basin City: a 5-year monitoring study in Heyuan, South China

Over the past decade, with the implementation of a series of prevention and control measures, the concentration of PM 2.5 at the surface in China has rapidly decreased. However, the issue of environmental ozone in the Guangdong-Hong Kong-Macao Greater Bay Area, which is located in South China, has begun to stand out, becoming a key factor affecting air quality. Currently, research on ground ozone pollution primarily focuses on super city clusters with high pollutant emissions, while there is comparatively limited research on the cities with lower emissions on the outskirts of the Pearl River Delta. This study utilized continuous automatic monitoring data for air quality and meteorological conditions from 2019 to 2023 to summarize ground-level ozone pollution events in Heyuan, South China, with a focus on the characteristics of ozone pollution and associated weather types. Over the five-year study period, a total of 39 ozone pollution days were observed in Heyuan, which mainly occurred in spring and autumn. Specifically, the annual number of ozone pollution days was 7 in 2019, 6 in 2020, 11in 2021, 10 in 2022 and 5 in 2023, with an annual average of 7.8 days. Additionally, low-level pollution, characterized by AQI values between 101 and 110, comprised a significant proportion (53.8%), suggesting substantial potential for further reduction of pollution events. By summarizing the meteorological drivers of ozone pollution in specific valley basin cities, this research supports authorities in executing regional joint controls and emission reductions to safeguard citizen health and mobility.