The Positive Effects of Linked Control Policy for Vessels Passing Through Locks on Air Quality—A Case Study of Yichang, China

During the waiting period before passing through locks, inland vessels typically rely on diesel generators to power their onboard equipment, which leads to air pollution and poses more direct threats to the surrounding residents and ecological environment. To assess the extent to which green and efficient lock passage strategies can reduce air pollution, this study takes the Linked Control Policy for Vessels Passing Through Locks released by the Three Gorges Navigation Authority in China in December 2017 as the research object. It collected air quality monitoring data for six years before and after the policy implementation (2014–2020) and used a Regression Discontinuity model (RD model) to analyze the policy’s effect. The results show that compared to 2014, the average concentration of SO2 in the air decreased by 67% in 2020, along with NO2 decreasing by 32%, PM2.5 by 42%, PM10 by 46%, and the AQI (Air Quality Index) by 27%. The robustness test of the RD model also confirmed the causal relationship between the policy implementation and the improvement in air quality. This research is the first to systematically disclose the environmental benefits of the “soft” management policy of optimizing the lock passage process, uncovering the positive influence of active ship lock passage policy on air quality, and providing a scientific basis for promoting the implementation of policies related to lock management.