The amount of a particular pollutant produced by an aircraft is a
function of the type of engines and the mode of operation of the aircraft [17]. An analysis must include a consideration of aircraft idling at the gate and runway threshold, engine power run-ups, taxiing, takeoff, climb-out, approach, and landing. The dispersion of the pollutants is studied through the use of either emission models or diffusion models. The emission model assumes a uniform dispersion of
the pollutants within the atmosphere of concern, whereas the diffusion model uses emissions or emission rates together with physical
and meteorological conditions to determine concentrations of pollutants. A study of the air quality impacts for an airport project requires a determination of ambient air quality, local meteorological conditions, the mix, number, and paths of aircraft using the airport, and the emission rate of the aircraft in different operating modes. It also requires a knowledge of the operating characteristics and volume of ground transportation modes providing access to and services at the airport, and the point sources of pollution occasioned by the normal operation of an airport. A flow chart of the interaction of those factors which are normally considered in an air quality study at an airport is given in Fig. 14-1. The results of an air quality study are typically
displayed on maps which show the before and after concentration of pollutants in the area of the airport, together with charts indicating the level of compliance with air quality standards.