Changes in global NO2 pollution by shipping during the COVID-19 lockdown: Implication for sustainable marine operations

Severe restrictions on human travel and consumption during the lockdown (LD) have affected global marine traffic and operations. The LD period is ideal for studying the emissions as there were restricted human activities. Although several pollutants are emitted by ships, the most important is nitrogen dioxide (NO₂), and can be considered an indicator of shipping emissions. Therefore, we examine the changes in NO₂ pollution over the shipping lanes, ports and coasts across the globe during LD. Here, we find a significant decline in NO₂ during LD over the major lanes, including the USA–Europe trade routes through the North Atlantic Ocean, Asia–Middle East through the Arabian Sea, Interasia, and Intereuropean through the North Sea and Baltic Sea, about 10–20%, as analysed form the TROPOMI satellite measurements. A similar reduction over the sea straight pass, such as the Cape of Good Hope and the Strait of Malacca is also estimated. Furthermore, the major global ports of Callao, Santos, Antwerp, Rotterdam, Busan, Tubarao, Richards Bay, Barcelona, Durban and Chennai exhibit a significant decrease in NO₂ during LD, about 30%. The decline in NO₂ over the shipping routes and ports can be attributed to reduced cargo, passenger, fishing and tanker vessel density due to the LD restrictions; consistent with the emission inventory analysis. Henceforth, this study suggests strict environmental policies in the shipping sector to curb emissions, as pollution is a great concern for public health in the port cities and coastal regions.