Air transport at low altitude affects air quality in the vicinity of airports. There are several types of impact and different methods to try and reduce this impact.
Like aircraft engines, airport activities produce nitrogen oxides (NOx) and particles, carbon monoxide (CO) and unburned hydrocarbons (HC) (e.g. from ground vehicles).
Contribution of different activities to Air France emissions at Paris-Charles De Gaulle:
Aircraft produce most low-altitude NOx, while ground vehicles produce most CO and HC.
Aircraft emissions are evaluated when the aircraft is in movement at low altitude (taxiing, taking off and landing), according to LTO cycles (Landing and Take-Off).
Two thirds of all nitrous oxide (NOx) emissions at low altitude come from LTO cycles, while the second-largest contributor is the road services that enable passengers and employees to reach airports. On the other hand, less than half our carbon monoxide (CO) and unburned hydrocarbon (HC) emissions come from aircraft activity.
CO and HC emissions have fallen by 50% and 90% respectively in the last 40 years, whereas it is hard to reduce NOx emissions (produced by high engine rotation, especially during take-off) without affecting combustion quality.
Technology improvements that have helped reduce CO2 and noise have, however, generated a larger quantity of NOx. Today, one of the challenges of the aviation industry is to find the right trade-off between CO2, noise and NOx.
At certain European airports (London, Stockholm, Zurich, Geneva and Mulhouse), the airport taxes paid by airlines depend on the emissions levels (NOx and HC) of their aircraft. A high-performance aircraft pays a lower fee while an aircraft that performs less well in terms of NOx and HC will pay more, sometimes in an overall revenue zero-sum game for the airport.