Spatiotemporal variations of NO2 and its driving factors in the coastal ports of China

Nitrogen Dioxide (NO2) is one of the major air pollutants in coastal ports of China. Understanding the spatiotemporal varying effects of driving factors of NO2 is vital for the implementation of differentiated air pollution control measures for different port areas. Based on the Ozone Monitoring Instrument (OMI) satellite data, we adopted a Geographically and Temporally Weighted Regression (GTWR) model to explore the influences of meteorological and socioeconomic factors on the NO2 Vertical Column Concentrations (VCDs) in coastal ports of China from 2015 to 2021. The results indicate that NO2 VCD in most ports has decreased since 2016 and the ports with serious NO2 pollution are mainly distributed in northern China. The associations between NO2 VCD levels and their drivers exhibit obvious spatiotemporal heterogeneity. Higher wind speed and relative humidity are more helpful to alleviate NO2 pollution in ports of the Bohai Rim and the Pearl River Delta. Cargo throughput has more closely associated with NO2 pollution in Beibu Gulf in recent years, yet there is no significant association found for Shanghai ports. The positive relationship between transportation emissions and NO2 VCD is more significant in southern ports. This work provides some implications for the formulation of targeted emission reduction policies for different ports along the Chinese coast.