Air quality at Stockholm Arlanda
The greatest air emissions at the airport are from air traffic and from road traffic to and from Stockholm Arlanda. Air emissions are also produced by service vehicles in the airport area, in the testing of aircraft engines, during firefighting exercises and in the production of the district heating used here. Air pollution levels at Stockholm Arlanda correspond to those found in a mid-size Swedish metropolitan area.
Since 1994, air pollution measurements have been taken at Stockholm Arlanda, and the results show, among other things, that:
- the levels of sulfur and nitrogen (which contribute to acidification) in precipitation are no higher per unit area at Stockholm Arlanda than in the county of Stockholm on average.
- fir and pine trees at Stockholm Arlanda lose needles to roughly the same extent as trees in the the
- levels of pollutants are highest by the terminals and roads with the most vehicular traffic.
The way air pollutants spread depends on a number of factors, including the direction of the wind, wind speed and temperature. So it is difficult to determine how large a share of pollutants affects the different areas.
Emissions from air traffic
Aircraft engines produce the same emissions as those produced in the burning of fossil fuel – carbon dioxide, nitrogen oxide, hydrocarbons, soot and other particles, carbon monoxide and sulfur dioxide.
Sometimes there may be a strong smell of jet fuel at the airport. What makes the jet fuel smell is sulfur impurities, known as mercaptans, which have an intense, penetrating and characteristic smell in very small concentrations.
These sulfur impurities belong to the same group of compounds that produce odour problems associated with the manufacture of paper mass (the sulfate process). Mercaptans are non-toxic in the low concentrations found at Stockholm Arlanda.
Aircraft whirlwinds are not fuel dumping
All aircraft leave whirlwinds in their wake. When it is humid out, the whirlwinds are visible because condensation is formed from the steam in the air. It may sometimes look as if the aircraft is dumping fuel while landing. The whirlwind in the wake of an aircraft is called a vortex.
Fuel dumping very rarely occurs and only in emergency situations when a plane needs to make an emergency landing. Only the largest aircraft are able to dump fuel. If dumping is necessary, it must be done over water and at such an altitude that the fuel vaporises before it reaches the ground.
Precedence is given to modern planes with lower emissions
One way to reduce emissions into the atmosphere from air traffic is by Stockholm Arlanda encouraging airlines to use modern aircraft that are better for the environment – take-off charges are lower the lower the level of nitrogen oxide and hydrocarbon emissions an aircraft engine produces. The aim is to induce airlines that have older planes with old engines to replace them with modern planes with cleaner engines.