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NARSTO Workshop on Innovative Methods for Emission Inventory Development and Evaluation University of Texas, Austin October 14-17, 2003 |
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Utilization of Tunable Infrared Laser Sensors for Cross-Road Mobile Source Emissions Characterization and Quantification
M.S. Zahniser, D.D., Nelson, J.B. McManus and C.E. Kolb
Aerodyne Research, Inc., Billerica, MA 01821-3976
Recent advances in laser sensor technology allow the characterization of on-road motor vehicle emissions utilizing real-time measurement techniques that do not rely on traditional tunnel studies or the require the lane restrictions often necessary to utilize commercial cross road remote sensing instruments. Quantification of a wide range of gaseous pollutants from individual on-road vehicles can be determined by utilizing tunable infrared laser differential absorption spectroscopy (TILDAS) techniques operating at ~0.01 s time resolution deployed in open path (cross road) configurations. Examples of TILDAS cross road remote sensing data will be presented along with recent instrumentation advances using quantum cascade lasers. Advantages of TILDAS remote sensing instrumentation include the ability to measure across multiple lane highways, the capability to redirect the optical system to measure low (light duty vehicle) and high (heavy duty diesel) exhaust plumes, and the ability to measure a wider range of exhaust pollutants in addition to the NO, CO and unspeciated VOC measurements accessible to commercial instruments, including NO2, N2O, NH3, and individual VOCs such as CH2O, CH4, C2H2, and C2H4. Compared to earlier lead salt tunable diode laser TILDAS instruments, the easier and more reliable spectral tuning and the great reduction or elimination of cryogenic cooling possible with quantum cascade (QC) lasers allow QC-TILDAS remote sensing instruments to be operated either autonomously or with greatly reduced operator attention.