Spatiotemporal characteristics and influencing factors of Air pollutants over port cities of the Yangtze River Delta

Bustling port activities give rise to serious air pollution in port cities of China’s Yangtze River Delta (YRD). Understanding the characteristics and driving forces of air pollutants over port cities of the YRD is conducive to the prevention and control of air pollution. This study analyzed the spatiotemporal characteristics and influencing factors of three air pollutants—PM2.5, NO2, and SO2—over coastal port cities (CPCs) and inland port cities (IPCs) in YRD from 2015 to 2020. The concentrations of air pollutants vary across geographic locations (low in the south/east and high in the north/west) and seasons (low in summer and high in winter). IPCs show higher pollutant concentrations than CPCs. The PM2.5, NO2, and SO2 concentrations over port cities in the YRD declined by 41.48%, 18.68%, and 64.8% from 2015 to 2020; CPCs have reduced more PM2.5 and NO2 than IPCs, while IPCs have reduced more SO2 than CPCs. There is a high synergy among the three air pollutants, with a stronger synergy found in CPCs. The impacts of wind speed and boundary layer height on air pollution are greater in CPCs than in IPCs. Concentrations of different air pollutants are strongly associated with emissions from different sectors. NO2 is the only one among the three air pollutants that cargo throughput shows a significant impact on, with the impact greater in CPCs than in IPCs. Findings from this study deepen the understanding of air pollution in port cities of YRD and may support air quality control in this area.