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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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Poster 11: On-Road Measurement of Automotive Particle Emission Factors by Ultraviolet Lidar and Transmissometer
Hans Moosmüller, Claudio Mazzoleni, Peter W. Barber,
Hampden D. Kuhns, Robert E. Keislar, and John G. Watson
Desert Research Institute, University of Nevada System, Reno, NV 89512
Emission factors are needed for tailpipe emissions of criteria pollutants from mobile sources. Such emission factors can be obtained with two complementary approaches: 1) measurement of emissions from a very limited number of vehicles under a large variety of operating conditions (examples are dynamometer studies, on-board instrumentation, or open plume measurements with chase vehicles) or 2) measurement of emissions from a large number (>105) of vehicles under a limited variety of operating conditions (examples are remote sensing, roadside, and tunnel studies). Only the remote sensing approach yields emission factors for a large number of individual vehicles. The resulting emission distributions across the fleet are needed for designing cost efficient emission reduction policies. While Vehicle Emissions Remote Sensing Systems (VERSS) for gaseous emissions have been used for more than a decade, no such system for measuring particulate matter (PM) emissions has been available.
A novel VERSS for the on-road measurement of fuel-based PM emission factors is described. This system utilizes two complementary PM channels using ultraviolet Lidar and transmissometry for the measurement of PM mass column content behind a passing vehicle. Ratioing the PM mass column content with the carbon mass column content, simultaneously measured with infrared absorption, yields the fuel-based PM emission factor. Transmissometry directly yields PM extinction coefficients without calibration, while the Lidar measurement of PM backscatter coefficients is calibrated through laboratory measurements of gases with well-known backscatter coefficients. The PM mass column content is calculated from these extinction and backscatter coefficients with the help of mass backscatter and extinction efficiencies obtained from theoretical calculations. This novel VERSS has been used extensively in a major air quality study and example data are presented.