Measurments of atmospheric pollutants
Bromma continuously measures the concentration of atmospheric pollutants in the form of nitrogen dioxide (NO2) and volatile organic compounds (VOCs) at three measuring points at the airport. Volatile organic compounds is an umbrella term for a number of pollutants that can be spread, for example, by wood fires and incomplete combustion of fuel from road and air traffic. The aim of the measurements is to study where the highest concentrations are found at the airport and make sure that no limit values are exceeded. The measurements show concentrations below the limit values in effect at all measurement points.
Emissions from air traffic
Aircraft engines produce the same kinds of emissions generated in the combustion of all fossil fuels: carbon dioxide, nitrogen oxides, hydrocarbons, soot, particulate matter, carbon monoxide and sulphur dioxide. Sometimes the air at the airport may smell strongly of jet kerosene. What makes it smell like kerosene is sulphur compounds, known as mercaptans, which have a penetrating, intense and characteristic smell in very small concentrations. Sulphur compounds belong to the same group of substances that create odour problems in conjunction with paper pulp production (using the sulphate process). Mercaptans are not toxic in the low concentrations found at the airport.
Soot and particulate matter are almost completely eliminated with modern aircraft engines. In Stockholm, it is mainly road traffic and wood fires that contribute to soot concentrations. That was a finding in the 2015 annual report on air in Stockholm, which the City of Stockholm Environmental and Health Administration produced in partnership with the air and noise analysis unit SLB-analys.
Questions regarding release of jet fuel
We are sometimes asked whether the aircraft that serve our airport release jet fuel on their approach and departure. They do not. None of the aircraft types that serve Bromma have the technological capability to release jet fuel by emptying their fuel tanks. Aircraft engines also have a high degree of efficiency, which means they produce minimal emissions of uncombusted fuel in flight.
All aircraft leave whirlwinds in their wake. When the weather is humid, the whirlwinds are visible since condensation is formed from water steam in the air. It may sometimes look like the aircraft is releasing fuel as it lands. 'Vortex is another term for the whirlwinds trailing the aircraft. Aircraft very rarely dump fuel and only in an emergency, when a fully fuelled plane needs to make an emergency landing. Only the largest aircraft have the ability to dump fuel. If fuel needs to be dumped, this should take place over water and at an altitude high enough to enable the fuel to be converted into steam before it reaches the earth.
Green approaches are also used at Bromma Stockholm Airport to the extent this possible. In a green approach, the aircraft descends at a continuous rate down to the landing runway. In doing so, it needs scarcely any jet thrust, which saves both fuel and emissions. About 30 per cent of the landings here are green landings from an altitude of 5,000 feet.
Certificate Stockholm Bromma Airport (pdf, in Swedish)