中国城市低碳治理的减污降碳协同效应——基于三批次低碳城市试点政策实施的准自然实验

As a pivotal policy instrument in China's ecological civilization construction during the new era, aimed at "reducing carbon emissions, controlling pollution, expanding greenery, and promoting economic growth", the low-carbon city pilot (LCCP) policy holds significant implications for achieving China's dual carbon goals and modernizing ecological environment governance. This study selects 265 prefecture-level cities in China from 2006 to 2021 as research samples, integrating pollution reduction and carbon mitigation, economic growth and green expansion, and government policy levels into a unified system. Utilizing a coupling coordination degree model, the study comprehensively evaluates the synergistic effects of pollution reduction and carbon mitigation, economic growth and green expansion, and government policies, analyzing the spatiotemporal differentiation characteristics of their coupling coordination degree. A multi-period difference-in-differences (DID) model is constructed to examine whether the LCCP policy promotes synergistic governance of pollution reduction and carbon mitigation across multiple domains, and to explore its intrinsic mechanisms at three levels: residential life, industrial production, and municipal behavior. The results indicate that: ①From 2006 to 2021, China's synergistic level of pollution reduction and carbon mitigation showed a significant upward trend, with Beijing's coupling coordination degree leading the nation at 93.869 and 92.687 in 2019 and 2021, respectively; ②The LCCP policy effectively achieves pollution reduction and carbon mitigation, with a marginal effect of 59.10%; ③ The LCCP policy's impact on pollution reduction and carbon mitigation is more pronounced in cities with high levels of digital transformation, and its synergistic governance effect is better in cities with lower industrialization levels compared to those with higher industrialization levels. Additionally, non-resource-based cities are more capable of achieving pollution reduction and carbon mitigation; ④Mechanism analysis reveals that the implementation of the LCCP policy can promote synergistic governance of pollution reduction and carbon mitigation by influencing residential life, industrial production, and municipal behavior, with the impact coefficients of the mechanism variables being significant at the 1% level. The construction of low-carbon cities should summarize successful experiences, adhere to local conditions, comprehensively develop smart, green, and low-carbon cities, and intensify low-carbon publicity to lay the foundation for achieving synergistic effects in pollution reduction and carbon mitigation.