Publication Date
2-2001
Document Type
Technical Report
Organizational Units
College of Natural Science and Mathematics, Chemistry and Biochemistry
Keywords
Atmospheric chemistry, Emissions, Pollutants
Abstract
The University of Denver has completed the second year of a five-year remote sensing study in the Denver area. The remote sensor used in this study is capable of measuring the ratios of CO, HC and NO to CO2 in motor vehicle exhaust. From these ratios, we calculate the percent concentrations of CO, CO2, HC and NO in the exhaust that would be observed by a tailpipe probe, corrected for water and excess oxygen not involved in combustion. Mass emissions per mass or volume of fuel can also be determined. The system used in this study was configured to determine the speed and acceleration of the vehicle, and was accompanied by a video system to record license plates. Measurements were conducted on 4 business days in late December of 1999 and early January of 2000 in Denver. The measurement site was the interchange ramp from northbound I-25 to westbound 6th Avenue in central Denver. A database was compiled containing 22,986 records for which the State of Colorado provided make and model year information. All of these records contained valid measurements for at least CO and CO2, and 22,867 records contained valid measurements for HC and NO as well. The database, along with earlier databases and reports, can be found at www.feat.biochem.du.edu. The mean CO, HC and NO emissions for the fleet measured in this study were 0.43%, 175 ppm and 511 ppm. These values are somewhat lower than the mean emissions for fleets measured by the University of Denver at the same site in the winters of 1996 and 1997, as part of a separate study, and in 1999, except for HC, which was lower in 1999. These lower emissions can be attributed to the current fleet consisting of more modern vehicles with advanced emissions control systems. As expected, the fleet emissions observed at the site in Denver exhibited a skewed distribution, with most of the total emissions contributed by a relatively small percentage of the vehicles. For example, the cleanest 89% of the fleet is responsible for only 33% of CO emissions. This skewed distribution was also seen in previous studies at the site. Using vehicle specific power, it was possible to adjust the emissions of the vehicle fleet measured in 2000 to match the vehicle driving patterns of the fleet measured in 1999. After doing so, the NO emissions of the 2000 fleet were lower than the emissions of the 1999 fleet. The apparent HC emissions were found to have increased probably because of an instrument noise problem, while CO remained relatively constant. A model year adjustment was applied to a fleet of specific model year vehicles to track deterioration. Using a fleet of 1982 to 1999 model year vehicles, the deterioration of the fleet was demonstrated for CO and HC. Tracking of model year fleets through four measurements in five years (including two years of this study) showed that the rate of emissions deterioration increases significantly after the vehicle has aged several years. An analysis of high emitting vehicles showed that there is considerable overlap of CO and HC high emitters, for instance 3% of the fleet emit 27% of the total CO and 22% of the total HC.
Copyright Statement / License for Reuse
Copyright Date
2-1-2001
Rights Holder
Sajal S. Pokharel, Gary A. Bishop, Donald H. Stedman
Provenance
Received from author
File Format
application/pdf
Language
English (eng)
Extent
33 pgs
File Size
196 KB
Publication Statement
Copyright is held by the author. User is responsible for all copyright compliance.
This research was supported by the nonprofit Coordinating Research Council, Inc. (CRC). The final results of the research conducted by, or under the auspices of, CRC are available to the public.
Recommended Citation
Pokharel, S. S., Bishop, G. A., & Stedman, D. H. (2001). On-road remote sensing of automobile emissions in the Denver area: Year 2. Atlanta, GA: Coordinating Research Council.