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Intensive seasonal sampling campaigns were undertaken at an urban location in Birmingham, U.K., in which high-volume samplers were used to collect particulate-and vapor-phase polycyclic aromatic hydrocarbons (PAHs) by means of filter papers and polyurethane foam plugs. Eighteen PAH species were determined by reversed-phase HPLC. Additionally, the suspended particle loading of the air was measured gravimetrically. Dichotomous stacked filter units (DSFUs) were run simultaneously with the high-volumes enabling the collection of particulate matter representative of fine (<2.1 µm) and coarse sized (2.1-10 µm) fractions. Filters from the DSFUs were analyzed for 19 metal species [by proton induced X-ray emission (PIXE)], ammonium, elemental carbon, and various anions. Metal and PAH concentrations were observed to be broadly in line with concentrations measured at other urban areas throughout the U.K. Chemical source apportionment studies took the form of principal component analysis (PCA) followed by multi-linear regression analysis (MLRA). This multivariate technique enabled major air pollution source categories to be identified along with the quantitative contributions of pollutant species to each source group. The results demonstrate that a combination of measurements of PAH and inorganic pollutants is a far more powerful tracer of emission sources than PAH data alone. PAH were found to be associated predominantly with emissions from road traffic, although other sources such as fuel oil, coal combustion, and incineration also contribute. Road traffic accounts for 88% of ambient benzo[a]pyrene at our site.

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Atmospheric aerosol formation is known to occur almost all over the world, and the importance of these particles to climate and air quality has been recognized. Although almost all of the processes driving aerosol formation take place below a particle diameter of 3 nanometers, observations cover only larger particles. We introduce an instrumental setup to measure atmospheric concentrations of both neutral and charged nanometer-sized clusters. By applying the instruments in the field, we come to three important conclusions: (i) A pool of numerous neutral clusters in the sub-3 nanometer size range is continuously present; (ii) the processes initiating atmospheric aerosol formation start from particle sizes of approximately 1.5 nanometers; and (iii) neutral nucleation dominates over the ion-induced mechanism, at least in boreal forest conditions.

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Road traffic is one of the main sources of particulate matter in the atmosphere. Despite its importance, there are significant challenges in quantitative evaluation of its contribution to airborne concentrations. This article first reviews the nature of the particle emissions from road vehicles including both exhaust and non-exhaust (abrasion and resuspension sources). It then briefly reviews the various methods available for quantification of the road traffic contribution. This includes tunnel/roadway measurements, twin site studies, use of vehicle-specific tracers and other methods. Finally, the application of receptor modelling methods is briefly described. Based on the review, it can be concluded that while traffic emissions continue to contribute substantially to primary PM emissions in urban areas, quantitative knowledge of the contribution, especially of nonexhaust emissions to PM concentrations remain inadquate.

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