ARB Research Seminar

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On-Road Motor Vehicle Emissions Including Ammonia, Sulfur Dioxide, and Nitrogen Dioxide

Gary A. Bishop, Ph.D., Department of Chemistry and Biochemistry, University of Denver

June 17, 2010
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Research Project


The three California cities of San Jose, Fresno, and West Los Angeles were visited during March 2008 to collect on-road emission measurements of carbon monoxide (CO), hydrocarbons (HC), nitric oxide (NO), ammonia (NH₃), sulfur dioxide (SO₂), and nitrogen dioxide (NO₂) from light-duty vehicles. At the San Jose and West Los Angeles sites comparison with historical measurements showed that emissions of CO, HC and NO continue to decrease in the on-road fleet yet the ratio of NO₂ to NO in new diesel vehicles appears to be under going large increases. A small fleet of 2007 diesel ambulances measured in Fresno was found to have more than 60% of their emitted oxides of nitrogen as NO₂. NH₃ emissions are shown to have a strong dependence on model year and vehicle specific power. NH₃ means of 0.49 ± 0.02, 0.49 ± 0.01 and 0.79 ± 0.02 g/kg of fuel for San Jose, Fresno, and West Los Angeles, respectively, with the larger emissions at the West Los Angeles site likely due to the driving mode at that location. NH₃ at these locations was found to account for 25%, 22% and 27% of the molar fixed nitrogen emissions. Using these mean values to construct a national fuel based NH₃ inventory results in a range of 210,000 to 330,000 short tons of NH₃ annually from light-duty vehicles.

Speaker Biography

Gary A. Bishop, Ph.D., is a research scientist of the Department of Chemistry and Biochemistry at the University of Denver. Since 1987 Dr. Bishop has been employed at the University of Denver, working with Professor Donald Stedman and his group. This group has specialized in developing spectroscopic instrumentation capable of remotely detecting vehicle exhaust. This equipment has been used to measure light-duty vehicle fleets in more than 21 countries and in more than 30 US locations. In addition the group has used these instruments to measure heavy-duty diesel trucks, commercial aircraft in London, snowmobiles in Yellowstone National Park and line-haul locomotives in Nebraska. This work has resulted in coauthoring 10 patents and more than 50 peer reviewed journal publications. He obtained his Ph.D. degree in bio-physical chemistry from the University of Colorado at Boulder in 1986.

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