Estimating aircraft emissions at Frankfurt airport using the DOAS technique

For the last decades, civil aviation traffic increased rapidly. At Frankfurt airport more than 700 flights depart per day (5h to 23h) i.e., take-offs take place approximately every two minutes. Like many other engines, an airplane’s engine uses fossil fuel primarily emitting carbon dioxide (CO₂) and water vapour (H₂O). However, high combustion temperatures also lead to a significant amount of nitrogen oxide (NO_x) emission. NO_x has a large impact on atmospheric chemistry and is harmful to human health. As airports are usually built in highly populated areas, these pollutants affect the health of the inhabitants in the region. Only few measurements have directly investigated emissions of airplanes under real atmospheric conditions during take-off as these measurements are typically difficult to perform.

In this work, we show the applicability and first results using Multi AXis Differential Absorption Spectroscopy (MAX-DOAS) measurements to directly determine airplane emissions during take-off at Frankfurt airport. Therefore, the MAX-DOAS instrument is mounted in extension of the runway, about 500 m below the typical altitude of the departing aircrafts to measure a spectrum of scattered sun light through the exhaust plume. Using a wide aperture of the entrance optics at one fixed elevation instead of scanning across the plume allows capturing the whole plume with one simultaneous measurement. In that way, the induced NO₂ emission of each passing aircraft can be determined. The obtained NO₂ emissions are then used to estimate the total emissions of nitrogen oxides.