Abstract
Motor vehicles in urban areas are the main source of ultrafine particles (diameters < 0.1 µm). Ultrafine particles are generally measured in terms of particle number because they have little mass and are prolific in terms of their numbers. These sized particles are of particular interest because of their ability to enter deep into the human respiratory system and contribute to negative health effects. Currently ultrafine particles are neither regularly monitored nor regulated by ambient air quality standards. Motor vehicle and bus fleet inventories, epidemiological studies and studies of the chemical composition of ultrafine particles are urgently needed to inform scientific debate and guide development of air quality standards and regulation to control this important pollution source. This article discusses some of the many challenges associated with modelling and quantifying ultrafine particle concentrations and emission rates for developing inventories and microscale modelling of motor vehicles and buses, including the challenge of understanding and quantifying secondary particle formation. Recommendations are made concerning the application of particle emission factors in developing ultrafine particle inventories for motor vehicle fleets. The article presents a précis of the first published inventory of ultrafine particles (particle number) developed for the urban South-East Queensland motor vehicle and bus fleet in Australia, and comments on the applicability of the comprehensive set of average particle emission factors used in this inventory, for developing ultrafine particle (particle number) and particle mass inventories in other developed countries.
Highlights
UFP have diameters less than 0.1 μm and are generally measured in terms of particle number due to their insignificant contributions to particle mass and prolific numbers
This section discusses (i) important factors influencing quantification of UFPs generated by motor vehicles and buses and (ii) issues related to the development of an UFP inventory prepared for an urban vehicle fleet in urban South-East Queensland, Australia, to identify current issues facing the development of UFP inventories and measurement campaigns and to discuss some possible approaches for inventory development
Motor vehicles and buses are a major source of UFPs in urban areas and these particle emissions pose health risks due to their ability to enter deep into the human respiratory system
Summary
UFP (ultrafine particles) have diameters less than 0.1 μm and are generally measured in terms of particle number due to their insignificant contributions to particle mass and prolific numbers. They have the ability to enter deep into the human respiratory system and contribute to negative health effects, making them a pollution source of particular interest. As the plume is diluted by ambient air its physical characteristics and chemical composition are significantly altered. Emission factors derived immediately upon particle plume formation are likely to exhibit different characteristics to those measured some period of time after emission, and will be subject to physical and chemical influences at the measurement site
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