Gas and Particulate Aircraft Emissions Measurements: Impacts on local air quality.

Air travel and freight shipping by air are becoming increasingly important and are expected to continue to expand. The resulting increases in the local concentrations of pollutants, including particulate matter (PM), volatile organic compounds (VOCs), and nitrogen oxides (NOX), can have negative impacts on regional air quality, human health and can impact climate change. In order to construct valid emission inventories, accurate measurements of aircraft emissions are needed. These measurements must be done both at the engine exit plane (certification) and downwind following the rapid cooling, dilution and initial atmospheric processing of the exhaust plume. We present here results from multiple field experiments which include the Experiment to Characterize Volatile Aerosol and Trace Species Emissions (EXCAVATE) and the four Aircraft Particle Emissions eXperiments (APEX- 1/Atlanta/2/3) which characterized gas and particle emissions from both stationary or in-use aircraft. Emission indices (EIs) for NOx and VOCs and for particle number concentration, refractory PM (black carbon soot) and volatile PM (primarily sulfate and organic) particles are reported. Measurements were made at the engine exit plane and at several downstream locations (10 and 30 meters) for a number of different engine types and engine thrust settings. A significant fraction of organic particle mass is composed of low volatility oil-related compounds and is not combustion related, potentially emitted by vents or heated surfaces within aircraft engines. Advected plumes measurements from in-use aircraft show that the practice of reduced thrust take-offs has a significant effect on total NOx and soot emitted in the vicinity of the airport. The measurements reported here represent a first observation of this effect and new insights have been gained with respect to the chemical processing of gases and particulates important to the urban airshed.