Recent studies have linked atmospheric fine particulate mater (PM25) with human health effects. In many urban areas, mobile sources are the dominant source of PM25. Dynamometer studies have also implicated diesel engines as being a significant source of ultrafine particles, which may also exhibit deleterious health impacts. In addition to direct tailpipe emissions, mobile sources contribute to ambient particulate levels via brake wear, tire wear, and the resuspension of articles from pavement. In order to characterise particulate emissions from in-use vehicles, the authors performed an on-road study of emission from vehicles operating in the Tuscarora Mountain Tunnel along the Pennsylvania Turnpike in May 1999. As part of this study chemical the following was obtained: chemically speciates size-segregated PM emissions from light-duty spark ignition and heavy-duty diesel vehicles; particle size distributions using a scanning mobility particle size analyser (SMPS); chemically speciated diesel profiles for use in source apportionment between diesel and other constitutents in ambient-air experiments; a comparison with years past how much improvement there has actually been in diesel particulate emission rates; and measurements of particulate emission rates from light-duty gasoline vehicles in order to evaluate the relative significance of this source. The experimental methods are described in this paper and the preliminary results presented of the on-road particulate emissions measurements. (A)
Abstract