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Air quality in airport approaches: impact of emissions from aircraft in ground run and flight

Air quality in airport approaches: impact of emissions from aircraft in ground run and flight

This project ran between 2005 and 2007. Development of infrastructure and the urban environment must be carefully managed if it is not to jeopardise air quality. To satisfy planning statutes and national and international directives, the impact of a major airport development on air quality as well as noise levels must be assessed (for example, as in the cases of Manchester Airport 2nd Runway and T5 Heathrow). Nitrogen oxides (NOx) and particulates are emitted in the exhaust streams of aircraft, road and service vehicles and power and heating plants, and may adversely affect human health and the environment. The White Paper on aviation ('The Future of Air Transport', DfT, 2003) predicted that a 5-7% mean annual increase in air-traffic movements is needed to meet demand, but, with only limited scope for reducing emissions from jet engines, it is possible that airport capacity in the UK may become constrained by air-quality requirements. The most difficult issue that has faced the construction of a third runway at Heathrow, for example, has been meeting statutory EU limits on NO2.

UV spectrometer in operation
at Manchester Airport
UV spectrometer in operation at Manchester Airport

Emissions from aircraft disperse as a result of processes additional to ambient atmospheric dynamics. A lateral diffusion is effected in the aeroplane wake. When the aeroplane is out of ground-effect, a pair of streamwise "wingtip" vortices rolls up in the wake and entrains emissions. An aeroplane exerts a downward force on the air, and so the wake must descend. The vortices thus relay emissions to the ground, far more efficiently than would otherwise occur through ambient processes alone.

Accurate predictions of aircraft emission transport require innovative measurement and modelling techniques that account for these complicating factors. The Department of Geography has been contributing to work in this area through application of optical remote sensing to measurement of aircraft during take-off and landing. Two field campaigns were carried out at Manchester airport, in 200 and 2006, with ultraviolet spectrometers deployed at the end of the runway to measure NOx emissions. The data will be used to validate a vortex-transport model, and to reveal the characteristics of the dispersion from aircraft in ground-effect.