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15 and soluble mass fraction. ARI focused on using an aerosol 2004, the prevailing wind shifted to the W/NW direction, and mass spectrometer and related supporting instruments to Missouri S&T and ARI moved to the eastern end of the south- quantify the composition of the particles as a function of size ern runways. In this work, exhaust plumes advected in the di- and thrust. Concurrent with the probe sampling, remote sens- rection of the sampling systems were continuously analyzed. ing was performed by NOAA using a mobile LIDAR system. Exhaust pollutant emission ratios relative to exhaust CO2 Also, NOAA supplied and operated the LIDAR, which used were determined for various gas-phase and particulate met- eye-safe ultraviolet light from a laser pulsing at 10 Hz and rics by looking at the concomitant rise in the measurement of scanned the beam up and down in a vertical plane perpen- a target pollutant above background with increased CO2. dicular to the direction of engine exhaust. The LIDAR system These emissions ratios were converted to fuel-based emis- was contained in a trailer positioned about 300 m (984 ft) sions indices using above-ambient CO2 as an internal exhaust from the aircraft. The principal wavelength for this project plume tracer. The characteristics of advected plumes--plume was 355 nm. The back scatter (or reflection) of energy from rise and plume spread (horizontal and vertical)--were meas- the laser by the total aerosols emitted by the aircraft engine ured using the LIDAR technique. These measured parameters was measured just behind the rear stabilizer of the aircraft by are key variables in dispersion modeling. the LIDAR. Upon completion of the dedicated engine testing, the 3.3 JETS-APEX2 research groups turned their attention to measurements of aircraft emissions on the airfield at various locations near the The impetus for the JETS-APEX2 study came from CARB. ends of runways where takeoff operations were occurring. In late 2004, CARB had initiated discussions with the With the exception of the data acquired on September 26, it Missouri S&T Center of Excellence for Aerospace Particu- was not possible to collocate the LIDAR and the Missouri late Emissions Research (Missouri S&T COE), the Port of S&T-ARI measurement systems. Despite this limitation, for Oakland for Oakland International Airport (OAK), and South- the overall project, both groups were successful in data col- west Airlines (SWA) to provide access to in-service commer- lection with 344 takeoffs measured by LIDAR and more than cial B737 aircraft for such measurements since SWA operates 500 taxi and takeoff events by the Missouri S&T-ARI meas- exclusively with B737s and is the major airline operating out urement system. of OAK. In the spring of 2005, Project JETS-APEX2 emerged The Missouri S&T and ARI mobile laboratories were po- as a study funded by multiple agencies (CARB, NASA, FAA, sitioned (with assistance from airport operations staff) just EPA, Missouri S&T, UCR, UCF, AEDC, GE, Boeing, SWA, downwind of an active runway, as shown in Figure 6. Two OAK, and ARI) to produce the first measurements with state- locations were selected to perform these measurements of-the-art analytical equipment of speciated total organic based on the prevailing wind direction on a given day. On gases (TOG) and PM from engines on typical in-use Boeing September 27, 2004, the prevailing wind was from the N/NE, 737-type commercial aircraft. and Missouri S&T and ARI were collocated on the western end JETS-APEX2 consisted of two series of experiments similar of the airport's southern runways. On September 28 and 29, to the Delta Atlanta-Hartsfield study. The first series focused Figure 6. Schematic of layout of mobile laboratories during the downwind study at Delta Atlanta-Hartsfield.

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16 on PM emissions in the vicinity of the exhaust nozzle of both old (-300 series) and new (-700 series) technologies. several different aircraft whose engines were cycled through Real-time PM physical characterization was conducted by a matrix of reproducible engine operating conditions as in Missouri S&T. Size distributions from 5 nm to 1 m were APEX1. The second series focused on emissions generated measured for all test points and associated aerosol parameters under actual operational conditions, conducted by placing the (i.e., geometric mean diameter, geometric standard deviation, mobile laboratories adjacent to, and downstream of, active total concentration, and mass and number-based emission runways. In these latter measurements, advected exhaust indices were evaluated). plumes generated by the mix of commercial transport aircraft ARI made real-time measurements of gaseous emissions taxiing and departing the airport during normal operations using: (1) tunable infrared laser differential absorption spec- were detected and analyzed. troscopy (TILDAS) based on both lead-salt diode and quantum The first series of experiments relied heavily on experience cascade laser sources for several important trace species gained in the previous APEX study where custom-designed emissions; (2) proton-transfer reaction mass spectroscopy probes and extensive support equipment were used to sample (PTR-MS) for HC; and (3) chemiluminescence measurement jet exhaust in the on-wing position at six thrust settings: for NO. These measurements were converted to emission 4%, 7%, 30%, 40%, 65% and 85%. In all, both engines of four indices using CO2 measured with a nondispersive infrared parked 737 aircraft were tested. absorption technique. Chemical composition of the particle Particle-laden exhaust was extracted directly from the emissions was quantified using an aerosol mass spectrometer combustor/engine exhaust flow through the probe, transported (AMS) in concert with a multi-angle absorption photome- through a sample train, distributed, and analyzed in each ter (MAAP, for black carbon mass) and particle size and group's suite of instrumentation. Sampling probes were located number measurements. at different positions downstream of the engine exit plane: The TOG, PM, metals, and ions were collected on filter 1 m, 30 m, and 50 m (3 ft, 98 ft, and 164 ft) on the starboard membranes by the University of CaliforniaRiverside Center side, and at 1 m (3 ft) on the port side of the aircraft. These for Environmental Research and Technology. Teflo filters aircraft engine emissions measurements were performed at the were used to acquire PM mass, and metals and ions concen- Ground Runup Enclosure (GRE) at OAK during August 2005 trations. For TOG, various sampling media--including (see Figure 7). The engine types were selected to represent SUMMATM canisters, 2,4-dinitrophenyl hydrazine (DNPH) Figure 7. Layout of the mobile laboratories in the GRE and probe rake assembly used in JETS-APEX2.