[Carbon Dioxide Mitigation Co-effect Analysis of Structural Adjustment Measures in the "2+26" Cities in the Jing-Jin-Ji Region and Its Surroundings].

The Three-Year Action Plan for Winning the Blue Sky Defense Battle states that structural adjustments of industrial, energy, transportation, and land use are important to significantly reduce CO₂ and air pollutant emissions. This co-effect is evident but has not been quantified at the city-cluster level. This study developed an emission inventory for the "2+26" cities of the Jing-Jin-Ji region and its surroundings and quantitatively analyzed the impacts of measures in the Three-Year Action Plan for Winning the Blue Sky Defense Battle on the emissions of CO₂ and major air pollutants using Greenhouse Gas and Air Pollution Interactions and Synergies in the "2+26" cities model (GAINS-JJJ). The results showed that in the "2+26" cities, the emission reductions in CO₂, primary PM_2.5, SO₂, NO_x, and NH₃ under policy scenario 2020 were 29.1 Mt (equivalent to 2% of the emissions in 2017), 203.8 (21%), 281.8 (27%), 485.5 (17%), and 34.3 kt (3%), respectively, relative to 2017. In terms of the cities or sectors, the higher the pollutant emissions, the higher the reduction achieved. The CO₂ mitigation co-effect results showed that industrial adjustment measures, such as eliminating backward production capacity, upgrades on industrial boilers, and phasing out small and polluting factories, contributed the most to the co-effect of CO₂ emission reduction, whereas NO_x presented the highest co-effects, with CO₂ among the different air pollutants.