The spatial heterogeneity of synergy and trade-off linkages between carbon and air pollutant mitigations in China's steel industry

The linkages between CO2 and air pollutant mitigations in the steel industry, including synergies and trade-offs, have significant spatial heterogeneities. Previous research has only investigated the linkages at the industrial level and overlooked the spatial heterogeneity features, which hinders the precise decision making on mitigation strategies. This study quantifies the linkages between CO2, SO2, NOx, and PM mitigations across cities in China's steel industry. A database of 3689 steel production units is established to calculate the emissions. Then, the linkages of mitigation targets of each city are quantified by setting the tailored mitigation pathways in 2019-2035. The results show that the emissions are highly spatially heterogeneous, as the top five contributing cities account for 27.7-33.2% of the total emissions of China's steel industry, but their emission efficiencies are not necessarily worse than the average. The mitigation pathways cause two-sided relationships, as 138 cities will earn mitigation co-benefits to varying degrees, but other 11 cities show the trade-offs. In addition, the mitigation pathway will lead to the highest economic costs as 51.2 billion CNY/a, bringing heavy economic burdens to some cities. This study enriches the co-mitigation management theory and supports the formulation of spatially differentiated mitigation targets and measures.