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Many researchers have reported the measurement of high numbers of emitted particles from gasoline vehicles operating at high speed. To date, in the absence of standard test protocols or analytical techniques, these measurements have all been made from a dilution tunnel set up according to regulatory procedures. Currently, there is great uncertainty relating to the use of the dilution tunnel as a suitable tool for the measurement of automotive particle size and number distribution and also the relevance of the procedure to ambient measurement of the same parameters. Gasoline particle number emissions, as measured on a dilution tunnel, are low at speeds under 120km/h. Beyond this speed, high numbers of very small particles have been measured. There is some evidence to show that these particles may be formed as an artefact within the sampling system, either from the desorption of deposited material or from the pyrolysis of other material in the sampling system itself.

Air quality monitoring of PM10 and associated health studies have focused interest on the size and the number of particles emitted to, and found in, the atmosphere. Automotive sources are one of the important elements in this, and CONCAWE have completed a study of heavy duty diesel particle emissions, complementing their previously reported light duty work. This heavy duty programme, presented here, investigated the nature of particulate emissions from two heavy duty engines (representative of different emissions levels), operating on three marketed fuels, over their respective European legislative heavy duty test cycles. The programme has investigated some of the complexities associated with obtaining credible data (e.g. dilution ratios, system stabilisation time etc.). The number distributions, which were measured over a wide size range (3 to 1000 nm), have been split into two size ranges, representative of nucleation mode and accumulation mode particles.

Certain polycyclic aromatic hydrocarbons (PAH) are carcinogenic and discussion will commence shortly in Europe on the development of an appropriate ambient air quality standard. With this proposed standard in mind, it is important to understand the contribution made by different emission sources to ambient PAH; this paper addresses only the contribution from automotive exhaust emissions. Methods for the sampling and analysis of particulate bound PAH from exhaust emissions, although not standardised, are well established. Vapour phase PAH however, are often neglected and need to be accurately quantified to assess the total contribution made by automotive sources to anthropogenic PAH emissions to the atmosphere. This paper describes the development of a technique applicable to the simultaneous collection and measurement of both vapour phase and particulate bound PAH in exhaust emissions. The final method selection focused on a filter/adsorbent trap sampler.