Air pollution, particularly SO2 emission, has become a global problem, seriously threatening the sustainable development and health of mankind. Based on the panel data of 248 prefecture-level cities in China during 2003–2008, this study used the Propensity Score Matching-Difference in Difference (PSM-DID) method within the counterfactual framework to evaluate the treatment effect of the policy made by the National Resource-Based Economic Transformation Comprehensive Supporting Reform Pilot Zone (CRZ) on sulfur dioxide (SO2) emissions. The results show the following. (1) The benchmark regression results demonstrate that the CRZ policy has significantly decreased per capita SO2 emissions (PCSO2) and SO2 emissions per unit of GDP (PGSO2) in the pilot zone, and the placebo test indicates that the evaluation of the policy effect is robust. (2) The dynamic effect test indicates that there is a lag in the effect of the CRZ policy on reducing SO2 emissions. The policy effect of the CRZ policy on PCSO2 and PGSO2 was not obvious in the first stage (2011–2015), the CRZ policy significantly reduced the PCSO2 and PGSO2 in the second stage of policy implementation (2016 and beyond), and the reduction effect of CRZ policy on SO2 emissions is increasing over time. (3) The mechanism analysis shows that optimizing industrial structure, increasing human capital, strengthening technological innovation, and expanding opening to the outside world are the main ways for the CRZ policy to reduce SO2 emissions. The study will help promote SO2 emissions reduction in Shanxi Province, providing a reference for the transformation and development of other resource-based cities in China and the world and contributing to accelerating the achievement of regional emission reduction targets and sustainable development.

Based on panel data on prefecture-level cities in China from 2003 to 2018, this study first estimates the treatment effect of the Shanxi Comprehensive Reform Area policy on 2.5 concentrations using a PSM-DID method. The empirical results show that, on average, the Shanxi Comprehensive Reform Area policy significantly increased the 2.5 concentrations of prefecture-level cities in Shanxi Province by 0.211% annually, and the place-based placebo test shows that the treatment effect obtained above is robust. Second, the dynamic effects show a continuous decrease in incremental effects during 2011-2018, gradually decreasing from a significant positive increment during 2011-2015 to a zero or even a negative increment during 2016-2018, indicating that the Shanxi Comprehensive Reform Area policy gradually increased in environmental friendliness. Third, the influencing mechanisms show that the Shanxi Comprehensive Reform Area policy influenced 2.5 concentrations by increasing the intensity of resource exploitation and decreasing the intensity of environmental regulations, but the capacity of scientific and technological innovations had no mediating effect on the relationship between the policy and 2.5 concentrations. Therefore, the government should further reduce the intensity of resource exploitation, strengthen the intensity of environmental regulations, and promote environmentally focused scientific and technological innovations to reduce 2.5 concentrations in Shanxi Province.

Based on panel data on 248 prefecture-level cities in China from 2003 to 2018, this study first estimates the treatment effect of the Shanxi Comprehensive Reform Area policy on PM 2.5 concentrations using a PSM-DID method. The empirical results show that, on average, the Shanxi Comprehensive Reform Area policy significantly increased the PM 2.5 concentrations of prefecture-level cities in Shanxi Province by 0.211% annually, and the place-based placebo test shows that the treatment effect obtained above is robust. Second, the dynamic effects show a continuous decrease in incremental effects during 2011–2018, gradually decreasing from a significant positive increment during 2011–2015 to a zero or even a negative increment during 2016–2018, indicating that the Shanxi Comprehensive Reform Area policy gradually increased in environmental friendliness. Third, the influencing mechanisms show that the Shanxi Comprehensive Reform Area policy influenced PM 2.5 concentrations by increasing the intensity of resource exploitation and decreasing the intensity of environmental regulations, but the capacity of scientific and technological innovations had no mediating effect on the relationship between the policy and PM 2.5 concentrations. Therefore, the government should further reduce the intensity of resource exploitation, strengthen the intensity of environmental regulations, and promote environmentally focused scientific and technological innovations to reduce PM 2.5 concentrations in Shanxi Province.