Accelerated reduction of air pollutants in China, 2017-2020

Emission regulations of the power and industry sectors have been identified as the major driver of PM_2.5 mitigation over China during 2013-2017. In this study, we use ground-based observations of four air pollutants (CO, NO₂, SO₂, and PM_2.5) to show that additional stringent emission policies on the industrial, transportation, and residential sectors during the new 3-year protection plan (2018-2020) have accelerated the improvement of China's air quality. Based on regional (North and South China) trends of annual mean measurements, significant reductions are observed for all four pollutants during 2017-2020. These decreasing trends are found to be >30% stronger than 2015-2017 for NO₂, CO, and PM_2.5. For CO and PM_2.5, the acceleration is the strongest in winter and North China, when and where the residential clean-heating actions were implemented. While for NO₂, the accelerations are pronounced regardless of region or season, reflecting nationwide measures to reduce NO_x emissions from industrial and transportation activities. SO₂ concentration reductions that were already substantial before 2017 are maintained but not accelerated, consistent with the dominance of end-of-pipe measures rather than a structural change of energy fuels. Our investigation highlights the value of multi-pollutant analysis to relate emission policies with air quality changes.