Measuring Ultrafine Particle Emissions

Image via WikipediaChallenges and Approaches for Developing Ultrafine Particle Emission Inventories for Motor Vehicle and Bus Fleets (21 page pdf, Diane U. Keogh and Darrell Sonntag, Atmosphere 2011, 2(2), 36-56, Mar. 24, 2011)

The research reviewed today looks at the factors that need to be considered when developing a system to collect and archive ultrafine particle data, taking into account both the characteristics of their emission and the potential health risks they pose for human health. Only one such inventory exists in the world - in Brisbane, Australia. As no air quality regulations exist for these particles and many cities depend on diesel buses for public transit, the requirement seems clear in order to begin to define and address this health threat.

Key Quotes:

“UFPs are not currently regulated by ambient air quality standards”

“The particle number emission rates for heavy-duty diesel vehicles are one to two orders of magnitude higher than gasoline-fueled passenger cars. In urban areas heavy duty diesel vehicles, including buses, are major sources of exposure for UFP”

“Colder temperatures significantly increase the concentration of UFP in motor vehicle exhaust measured from the roadside [58], on-road and on-board vehicle dilution tunnels”

“Concentrations of UFPs generated by motor vehicle fleets tend to be higher within 100 metres of the emission source under typical meteorological conditions. Studies have shown that particle concentration decreases with distance from the road up to around 300 metres”

“although heavy duty vehicles contributed only 6% of total vehicle kilometers traveled in the study region, this vehicle class contributed more than half the region’s particle number (ultrafine particle) and PM1 emissions due to their high emission rates”

“particle number emission rates (particle number/second) were highest for the buses on high-speed freeway driving conditions. When the bus route was divided into 50-meter segments, the segments in which the bus emitted the most particles occurred near bus stops and intersections where the bus was accelerating from stop”

“bus idling time needs to be considered as emission hot spots can occur where heavy-duty diesel vehicles idle for extended periods ..and how close the path chosen by (or available to) pedestrians is to the traffic source or to accelerating buses and acceleration distances”

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