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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.

The effect of pre-catalyst speciation on lean NOx catalysis was investigated using a chemically defined fuel matrix. Nine model fuels and a diesel fuel were injected into the exhaust stream of a medium duty diesel engine prior to a DeNOx catalyst. NOx conversions ranged from 9% at a mid speed and load test point to 43% at a higher load test point. On an absolute basis, model fuels produced up to 34% greater NOx conversions relative to diesel. Speciation revealed that, compared with low temperature test points, cracking and oxidation at peak torque significantly modified the auxiliary HC input to the catalyst. The quantity of ‘cracked’ derivatives of the auxiliary fuel, namely alkene and carbonyl species, correlated well with NOx conversions.