Can voluntary environmental policies reduce surface black carbon concentrations? evidence from low-carbon city construction

Sustainable development is critical for the long-term growth of cities. Achieving harmonious development between the economy and the environment is an important goal pursued jointly by nations and cities. Environmental policies serve as a key driving force supporting cities in accomplishing low-carbon and green transitions. However, existing literature has insufficiently explored the impact of non-mandatory environmental policies on regional Surface Black Carbon Concentrations (SBC), and no consensus has been reached. SBC refers to the monthly data of black carbon mass concentration in Chinese cities, derived from NASA's M2TMNXAER_5.12.4 satellite retrieval data, specifically the natural logarithm of surface black carbon mass concentration (μg/dm³). Therefore, this study uses city-level panel data from China spanning 2000–2021 to examine the logical relationship between non-mandatory Low-Carbon City Pilot (LCCP) policies and SBC in cities. The findings demonstrate that low-carbon policies can generate an SBC reduction effect. A series of robustness tests provide evidence of the negative causal impact of LCCP policies on SBC. Mechanism analysis reveals that green innovation and industrial upgrading serve as two primary transmission channels.