Near-surface ozone pollution, associated with complex responses to changing precursor emissions and meteorological conditions, has become one of the biggest challenges in China’s air quality management. Here, we present the spatiotemporal evolution of ozone concentrations from 2010 to 2021 using measurements of the national air quality monitoring network. We evaluate the effectiveness of the national air pollution control programme, including Phase 1 (2013–2017) and Phase 2 (2018–2021), in reducing the ozone level over China, using an optimized machine learning approach, high-resolution emission estimates and an improved air quality model. We find that while emission changes in Phase 1 increased the ozone level over the five highly developed regions, further reductions of nitrogen oxide emissions in Phase 2 have generally constrained the ozone pollution. The changing effect of emission controls on ozone pollution is due to the shift in the prevailing regime for ozone formation and the weakened effects of aerosol declines, as emission reductions continue. We further find that current emission controls have been more effective in rural locales in four of the five regions, and more effective in summer than winter. Therefore, further control of ozone pollution should consider these regional and seasonal variations to identify the most important precursors for the pollution.
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Extended Data Fig. 1 Time series and interannual trends of MDA8 ozone concentrations for East China during 2010–2012, 2013–2017 and 2018–2021 for urban (a) and rural areas (b).
The smooth grey lines and dotted purple lines represent time series of predicted and observed MDA8 ozone averaged for each month, respectively. The black, blue and red lines represent the linear trends of MDA8 ozone for 2010–2012, 2013–2017 and 2018–2021, respectively. The annual variation rates (μg/m3/yr) during different periods, with significance levels (*p < 0.05) are presented (The numbers in the parentheses indicate the relative annual variation rate (%/yr)). Summer indicates June-August and winter indicates December-February.
Extended Data Fig. 2 The difference in CMAQ-simulated MDA8 ozone for East China due to the anthropogenic emission change from 2013 to 2017 (a) and 2018–2021 (b).
The meteorological field is fixed at 2017 level in the simulation.
Extended Data Fig. 4 The growth of MDA8 ozone-PM2.5 partial correlation coefficients (PCORs) and the decline in PM2.5 concentrations for the five key regions during 2013–2021.
The solid blue lines and solid green lines indicate the time series of MDA8 ozone-PM2.5 PCORs and PM2.5 concentrations, respectively. The dashed blue lines indicate the linear trends of MDA8 ozone-PM2.5 PCORs. The annual growth rates of PCORs with significance levels (*p < 0.05) are presented.
Extended Data Fig. 5 Spatial distribution of the simulated MDA8 ozone (μg/m3) responding to the changes in the effects of aerosol in summer from 2013 to 2021.
The aerosol affects ozone via altering photolysis rates (a) and all heterogeneous reactions (b).
Extended Data Fig. 6 The differences in winter (December) MDA8 ozone simulated with and without the aerosol effect in CMAQ are presented for 2013 (a), 2017 (b), and 2021 (c).
The national average ‘efficiency’ of aerosol suppression on MDA8 ozone (that is, ΔCO3/CPM2.5) is given in the bottom left corner of each panel.
The evolution of monthly average MDA8 ozone concentrations (a), and monthly distributions of satellite-derived TVCD of HCHO (b) and NO2 (c) during 2010–2021 are shown for East China. The data source of TVCD is described in the Methods of the article.
Gridded data of average warm-season MDA8 ozone concentration during 2010–2021.
Interannual changes of MDA8DEMET in urban and rural areas for different regions for 2013–2021.
Annual variation rates of MDA8DEMET for Phase 1 and Phase 2 at monthly scale over different regions.
Gridded data of shifts in ozone formation regime between 2013 and 2021 for different regions and seasons; the fractions of total area undergoing different types of regime shift by season for the five key regions.
Gridded data of the effect of aerosol reduction on ozone enhancement.
Interannual changes of MDA8 ozone concentrations for East China during different periods for urban and rural areas.
Gridded data of the difference in CMAQ-simulated MDA8 ozone for East China due to the anthropogenic emission change from different periods.
MDA8 ozone, satellite-based NO2 and HCHO TVCD in different regions and years.
Partial correlation coefficients of MDA8 ozone-PM2.5 and the PM2.5 concentrations for the five key regions during 2013–2021.
Gridded data of simulated MDA8 ozone concentrations responding to the changes in aerosol effects in summer from 2013 to 2021.
Gridded data of the differences in winter MDA8 ozone simulated with and without the aerosol effect in CMAQ model.
Monthly average MDA8 ozone concentrations and satellite-derived TVCD of HCHO and NO2 during 2010–2021 for East China.
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Wang, Y., Zhao, Y., Liu, Y. et al. Sustained emission reductions have restrained the ozone pollution over China. Nat. Geosci. 16, 967–974 (2023). https://doi.org/10.1038/s41561-023-01284-2