You can see the same pattern as in the English Channel, in the Antwerp and Rotterdam areas. My guess is higher traffic of ships probably running at lower speed

You can see the same pattern as in the English Channel, in the Antwerp and Rotterdam areas. My guess is higher traffic of ships probably running at lower speeds (higher concentration of gases in the same volume). Ships are also meant to change from crude bunker fuel (which spews really high concentrations of SO2) to finner diesel fuel (which spews high concentrations of NO2) when they get closer to ports. It's a case of choose your poison with shipping, SO2 kills you now, NO2 kills you in the long run (it reduces human lifespan)