Heterogeneities in Regional Air Pollutant Emission Mitigation Across China During 2012-2020

The toughest-ever clean air actions to date in China have helped to reduce national air pollutant emissions significantly in recent years. However, the heterogeneous mitigation paths and their determinated factors among regions were less concerned. To direct regional mitigation strategies more efficiently, we compiled a time-series emission inventory of Chinese 30 provinces for SO2, NOx, primary PM2.5 and CO2 at detailed socioeconomic sectors, and then used spatial-temporal index decomposition analysis to evaluate the driving forces for changes in regional pollutant emissions and emission intensities from 2012 to 2017 and from 2017 to 2020, separately. Our results showed that end-of-pipe control measures dominated the decreasing trend of China's pollutant emissions (38%-68% for SO2, NOx, and primary PM2.5), but their relative dominance diminished gradually, and the effects from energy policy emerged, even outweighing the former in southern areas during the second phase. Though driven by different factors, the chemistry, nonmetal, metal, energy and residential sectors dominated regional reduction trend and with varying degrees. Clean air action led to the convergence of regional emission intensity, while optimizing and upgrading industrial structure and improving energy efficiency is still necessary for further reduction in northern and western areas at present. To mitigate the severe air pollution in recent year, regions in China enforced differentiated reduction targets and mitigation strategies, as they experienced different development stages, energy and industrial structures, and levels of pollution. To direct regional mitigation actions more efficiently, we compiled a province- and sector-specific air pollutant inventory for 2012, 2017, and 2020, and then quantified the contribution of various socioeconomic factors to the changes of regional emissions and their emission intensity during 2012-2017 and 2017 to 2020, separately. Our result shown that, end-of-pipe control measures contributed the largest reduction of pollutant emissions in China, but with the reduction rate increasing, its marginal utility decreased, and the relative effect from energy policy measures increased, even outweigh the effect from end-of-pipe control measures in southern China. The chemistry, nonmetal, metal, energy and residential sectors contributed the most emission reduction national widely; while, as with different industrial attributes, they were driven by different factors among regions and species. End-of-pipe control measures and energy policy have reduced the gap of emission intensities in almost all regions, but the pollution-intensive industrial structure and low energy efficiency still were significant in northern and western China, and prevented their further emission reduction. Driving forces for changes of Chinese air pollutant emissions during two stages between 2012 and 2020 were evaluated at different scales End-of-pipe control measures dominated the decreasing trend (38%-68%) but with diminished effect, and the relative effect from energy policy increased Emission intensities converged among regions, industrial structure and energy efficiency need further improvement in north and west China