Covid –19 restrictions expose air traffic at the Munich Airport as hotspot of ultrafine particle pollution – implications for regional air quality/Covid-19 Restriktionen entlarven den Flugverkehr am Flughafen München als größte Quelle der Ultrafeinstaubbelastung – Implikationen für die regionale Luftqualität

The massive decline of air traffic in consequence of the Covid-19 pandemic allowed a detailed analysis of aviation induced noise and particularly air pollution caused by kerosene combustion. As expected, aircraft noise is reduced significantly particularly during daytime. Notably, the particulate matter PM2.5 and PM10 officially measured as pollution load at airports is proven to be almost unchanged in ambient air. As jets do not emit coarse fine dust but solely ultrafine particles smaller than 0.1 µm (UFP), this result is no surprise. However, the dramatic reduction of ultrafine particle concentration under reduced air traffic is exemplified e.g. by 7,100 UFP/cm3 in April 2020 while in February 2020 at the Munich Airport center still 54,200 UFP/cm3 were measured. Assuming an UFP background concentration of 5,000 UFP/cm3, a decline of air traffic by 93% reduced UFP by the same magnitude. Measuring the downwind plume of the airport at varying distances the number of particles decreases while the particle size increases which is based on the fact that aircrafts emit only smallest UFP which intermix with bigger UFP from other sources around the airport. Effective measures to prevent UFP emissions are urgently needed. In addition to the use of sulfur-free kerosene, towing the aircraft during all taxiing procedures is the most effective measure to reduce UFP on ground. This work fostered the development of https://10nm.de/, which intends to provide a simulation of the potential UFP load at any airport based on wind conditions like wind direction and wind speed.