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In-situ measurements of various properties of traffic-related aerosol particles have been performed with a mobile laboratory. The measured aerosol quantities include particle chemical composition (sulfate, nitrate, total organic matter, ammonium, black carbon) as well as particle size distributions covering diameters from 10 to 300nm, and total particle number density. Additionally, gas phase emissions (CO2, NO, NO2) were monitored. We performed six measurement drives in the vicinity of the city of Aachen (population ca. 260,000) at 50.8°N, 6.1°E in Germany on motorways, rural roads, and in the inner city of Aachen in June 2005. The results indicate that the main influence of traffic on the aerosol properties results in soot particles coated with organic matter, having a modal diameter around 100nm (“soot mode”). The abundance of these particles was found to be highest in the inner city traffic. Nucleation mode particles (around 30nm) have been observed occasionally during truck chasings on motorways. These particles consisted mainly of organic compounds but included possibly also a sulfuric acid core. Data observed under “motorway background” conditions were similar to the rural regional road data. Highest number concentrations have been observed during truck chasings. Comparison between non-refractory (here with respect to 600°C) and total particle volume indicated a higher contribution of refractory material under all traffic-influenced conditions compared to rural road data. Fuel specific emission ratios were derived for a subset of 18 truck-chasing experiments, yielding (8.3±5.8)×1015 kg−1 for particle number, 224±136mgkg−1 for black carbon, 125±125mgkg−1 for organic matter, 17±12gkg−1 for NO and 18±14gkg−1 for NO x (mean values and standard deviations). [Copyright &y& Elsevier]

A single-particle mass spectrometer (LAMPAS-2) was operated at an Autobahn (high-speed highway with significant heavy-duty diesel traffic), an urban and a rural site in the vicinity of Aachen (Germany). The single-particle mass spectra could be classified into eight classes, representing different types of mineral particles, inorganic salt particles, and carbonaceous aerosol particles. At all three sites characteristic patterns of diesel exhaust particles with and without secondary compounds (ammonium sulfate/nitrate) were observed. The relative contribution of diesel soot to the number of 0.5 μm particles was 23% or 35% at the rural and the Autobahn site, respectively. The absolute number of diesel exhaust particles was three times larger at the Autobahn site. At the urban site the diesel exhaust particle contribution ranged from 10% to 35%, depending on the local operation of heavy-duty construction vehicles. Elemental carbon and carbonaceous particles made up the majority number of the 0.5 μm particles, and showed a decreasing percentage towards 2 μm particle size. As expected mineral-soil-derived particles showed the reverse size distribution. The data sets were also analyzed using a reference pattern obtained from exhaust particles of a light-duty diesel vehicle as a fingerprint. A similar trend of the contribution to the diesel-exhaust-like particle class was found, although the absolute numbers were somewhat different. On-line single-particle mass spectrometry proved to be a promising tool to identify individual particles if characteristic reference spectra were available. [Copyright &y& Elsevier]