Evaluating spatiotemporal variations and exposure risk of ground-level ozone concentrations across China from 2000 to 2020 using high-resolution satellite-derived data

Abstract

Understanding the spatial and temporal characteristics of both long- and short-term exposure to ground-level ozone is crucial for refining environmental management and improving health studies. However, such studies have been constrained by the availability of high-resolution spatiotemporal data. To address this gap, we characterized ground-level ozone variations and exposure risks across multiple spatial (pixel, county, region, and national) and temporal (daily, monthly, seasonal, and annual) scales using daily 1 km ozone data from 2000 to 2020, derived from satellite-sourced land surface temperature data via a machine-learning hindcast method. The model provided reliable estimates, validated through rigorous cross-validation and direct comparison with external ground-level ozone measurements. Our long-term estimates revealed seasonal shifts in high-exposure ozone centers: spring in eastern China, summer in the North China Plain (NCP), and autumn in the Pearl River Delta (PRD). A non-monotonic trend was observed, with ozone levels rising from 2001–2007 at a rate of 0.47 µg m−3 yr−1, declining after 2008 (−0.58 µg m−3 yr−1), and increasing significantly from 2016–2020 (1.16 µg m−3 yr−1), accompanied by regional and seasonal fluctuations. Notably, ozone levels increased by 0.63 µg m−3 yr−1 in summer in the NCP during the second phase and by 6.38 µg m−3 yr−1 in autumn in the PRD during the third phase. Exposure levels over 100 µg m−3 have shifted from June to May, and levels exceeding 160 µg m−3 were primarily seen in the NCP, showing an expanding trend. Our day-to-day analysis highlights the influence of meteorological factors on extreme events. These findings emphasize the need for increased public health awareness and stronger mitigation efforts.