Exploration of port environmental efficiency measurement and influential factors in the Yangtze River Delta Pilot Free Trade Zone.

This study focuses on the environmental efficiency of ports in China's Yangtze River Delta Pilot Free Trade Zone (YRD PFTZ), a critical factor in advancing the high-quality development of ports and facilitating Chinese-style modernization. Current research on port efficiency primarily focuses on the geographical level, with relatively few studies examining the economic regional framework. We selected the YRD PFTZ port for our study to address this gap. Covering 2013 to 2021, we employed the Super-SBM with undesirable outputs and utilized the GML index method. We conducted a spatiotemporal analysis to assess dynamic and static aspects and used the Tobit model to thoroughly investigate the factors influencing the GML Index of these ports. The study showed that: (1) the overall environmental efficiency of these ports was relatively high with a fluctuating trend of initial increase, followed by a decrease, and then an upturn. (2) From a dynamic perspective, the average Green Total Factor Productivity (GTFP) Index is 1.549, denoting an exceptional level primarily driven by technological efficiency. The technical efficiency change index is the main factor improving GTFP in Shanghai, Jiangsu, and Anhui provinces. (3) The port cargo volume and total import and export volume significantly impact the environmental efficiency.