NERL Research Abstract KPA's Nnlioiiiil Kxposurc Ucscnrch l.nbornlorv (il'UA (ionl I - Clean Air APM #521 Significant Research Findings New Particulate Matter2 5 Profiles for Mobile Source Emissions Scientific Emissions from motor vehicles have been identified as a major contributor to Problem and ambient particulate matter (PM) and other pollutant concentrations in U.S. Policy Issues J urban areas. Consequently, for many years motor vehicles have been a major target for regulations and control technologies aimed at reducing their emissions. As measured by mobile source emissions inventories, these efforts have resulted in significant improvements, in spite of substantial increases in VMT (vehicle miles traveled) over the same period. The difficulties of constructing accurate emissions inventories are well known, however, and it is important to provide alternative means of verifying and quantifying changes in the contributions of mobile source emissions to current air quality. Receptor modeling can perform this function by utilizing the measured atmospheric concentrations of mobile source-tracing chemical species and comparing their concentrations to the relative abundances (source profiles) of the species found in mobile source emissions. This project's objective was to provide an up-to- date set of source profiles for light-duty gasoline and heavy-duty diesel vehicles. One of the standard methods used to obtain mobile source profiles is to take measurements in motor vehicle tunnels. In this study, measurements were taken in the Ft. McHenry tunnel in Baltimore, MD, over a one-week period in September, 1998. Sampling was performed separately in two traffic tubes, one carrying heavy-duty diesel trucks, the other carrying mostly gasoline-powered passenger and other light-duty vehicles. Samples were also collected outside the tunnel to provide background correction information on the ambient air entering the tunnel that contributed to the samples collected. The samples were analyzed for a variety of chemical species including organic and elemental carbon, a large number of elements from aluminum to lead, and a large number of organic compounds (e.g., C10 - C40 alkanes). Research Approach National Exposure Research Laboratory - September 2000 ------- Results and The measurements have been assembled in a database that can be queried to Implications obtain truck and car source profiles containing constituent chemical species as may be desired by a user. Overall, the chemical source profiles derived from the two traffic tunnels show distinct differences: the alkane distribution for cars shows a maximum occurring at a larger carbon number than for trucks; the elemental carbon (black soot) component in the truck profile is much more prominent than for the car profile, and; the elemental iron component is prominent in both, but more so in the car profile. These features, among others, should allow the use of these profiles, with receptor modeling techniques, to separate the contributions that the two vehicle categories make to ambient air concentrations. and Publications Research The field work and subsequent chemical analyses occurred through the Collaboration collaborative efforts of researchers at NERL, the Florida Department of Environmental Protection, and the Universities of Michigan, Miami, and Maryland. Aspects of the work are described in the publications that follow. Keeler, G.J, Dvonch, J.T., Barres, J.A. Mobile Source Profile Determination: Ft. McHenry Traffic Tunnel Study Mercury Data Report to Florida Department of Environmental Protection. 1999. Milne, P., Haring, J., Zika, R., Ondov, J., Keeler, G., Stevens, R. High Molecular Weight Alkane and Hydrocarbon Speciation in Fine Aerosol Particles: A Vehicle-Segregated Tunnel Study from Baltimore (extended abstract). Presented at: PM2000: Particulate matter and Health-The Scientific Basis for Regulatory Decision-Making. Specialty Conference and Exhibition. January; Charleston, S.C. Pittsburgh, PA: Air& Waste Management Association. 2000. Lewis, C.W., Landis, M.S. Ft. McHenry Tunnel Mobile Source Profiles Data Base: Description and Use. (Tunnel_data_summary.xls). 2000. A comprehensive manuscript based on the measurements obtained in this project is anticipated to be submitted to a peer-reviewed journal during FY01. One of the first applications of the profiles will be in a major air quality study in the Tampa, FL, region beginning in 2001 that will provide a field test of the applicability of source apportionment models. Inquiries about this project, as well as NERL's receptor modeling research program, can be directed to: Charles W. Lewis, Ph.D. U.S. Environmental Protection Agency National Exposure Research Laboratory (MD-47) Research Triangle Park, NC 27711 Phone: (919)541-3154 E-mail: lewis.charlesw@epa.gov Future Research National Exposure Research Laboratory - September 2000 ------- |