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EMISSIONS OF METALS ASSOCIATED WITH MOTOR VEHICLE ROADWAYS
Citation:
LOUGH, G. C., J. J. SCHAUER, J. PARK, M. M. SHAFER, J. T. DEMINTER, AND J. P. WEINSTEIN. EMISSIONS OF METALS ASSOCIATED WITH MOTOR VEHICLE ROADWAYS. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 39(3):826-836, (2005).
Impact/Purpose:
The main research question guiding this task is "how do mobile source emissions impact public health and the environment." The main objectives of this task include:
(1) Identify spatial and temporal variability in pollutant concentrations near major mobile source emission locations such as urban roadways and non-road activities.
(2) Characterize real-world emissions from on- and non-road mobile sources for use in identifying hazardous components and developing and improving mobile source emissions and human exposure models.
(3) Develop mobile source emission profiles and markers for use in human exposure and air quality receptor models.
(4) Determine the impact of emerging technologies (fuels and engine systems) on emissions and exposures to toxic pollutants.
(5) Develop and improve analytical methods that measure emissions from mobile sources.
Description:
Emissions of metals and other particle-phase species from on-road motor vehicles were measured in two tunnels in Milwaukee, WI during the summer of 2000 and winter of 2001. Emission factors were calculated from measurements
of fine (PM2.5) and coarse (PM10) particulate matter at tunnel entrances and exits, and effects of fleet composition and season were investigated. Cascade impactors (MOUDI) were used to obtain size-resolved metal emission rates. Metals were quantified with inductively-coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence (XRF). PM10 emission rates ranged from 38.7 to 201 mg km-1 and were composed mainly of organic carbon (OC, 30%), inorganic ions (sulfate, chloride, nitrate, ammonium, 20%), metals (19%), and elemental carbon (EC, 9.3%). PM10 metal emissions were dominated by crustal elements Si, Fe, Ca, Na, Mg, Al, and K, and elements associated with tailpipe emissions and brake and tire wear, including Cu, Zn, Sb, Ba, Pb, and S. Metals emitted in PM2.5 were lower (11.6% of mass). Resuspension of roadway dust was dependent on weather and road surface conditions, and increased emissions were related to higher traffic volumes and fractions of heavy trucks. Emission of noble metals from catalytic converters appeared to be impacted by the presence of older vehicles. Elements related to brake wear were impacted by enriched road dust resuspension, but correlations between these elements in PM2.5 indicate that direct brake wear emissions are also important. A submicrometer particle mode was observed in the emissions of Pb, Ca, Fe, and Cu.