 |
NARSTO Workshop on Innovative Methods for Emission Inventory Development and Evaluation University of Texas, Austin October 14-17, 2003 |
 |
Separating the Contribution of Gasoline and Diesel Vehicles
to Ambient Fine Particle Levels: Verification of Results from Receptor Models
M. P. Fraser1 *, B. Buzcu1, Z. W. Yue1, G. R. McGaughey2, N. R. Desai2, D. T. Allen2, R. L. Seila3,
W. A. Lonneman3 and R. A. Harley4
1 Department of Civil and Environmental Engineering, Rice University, Houston, TX 77005
2 Center for Energy and Environmental Resources, University of Texas, Austin, TX 78758
3 U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
4 Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720
The ability to separately track emissions of fine particles from gasoline and diesel powered vehicles has received significant attention as studies of the health effects of particles have shown diesel particulate matter to be highly toxic and mutagenic. One method used for this is receptor modeling. To answer whether the receptor models use can correctly separate emissions from gasoline and diesel vehicles, samples of fine particulate matter were collected in a roadway tunnel near Houston, TX during two separate sampling periods: one sampling period from 1200-1400 local standard time and one sampling period from 1400-1600 local standard time. During the two sampling periods, the tunnel traffic contained roughly equivalent numbers of heavy-duty diesel trucks. However, during the late afternoon sampling period, the tunnel contained twice as many light-duty gasoline-powered vehicles. The effect of this shift in the vehicle fleet affects the overall emission index (grams pollutant emitted per kilogram carbon in fuel) for fine particles and fine particulate elemental carbon. Additionally, this shift in the fraction of diesel vehicles in the tunnel is used determine if the chemical mass balancing techniques used to track emissions from gasoline-powered and diesel-powered emissions accurately separates these two emission categories. The results show that the chemical mass balancing calculations apportion roughly equal amounts of the particulate matter measured to diesel vehicles between the two periods, and attribute almost twice as much particulate matter in the late afternoon sampling period to gasoline vehicles. Both of these results are consistent with the traffic volume of gasoline and diesel vehicles in the tunnel in the two separate periods and validate the ability for organic molecular markers to separate these two primary sources of fine particles.