Particle-phase polycyclic aromatic hydrocarbon emissions from non-catalysed, in-use four-stroke scooters.

The emissions of particle-phase polycyclic aromatic hydrocarbons (PAHs) were evaluated in the exhaust of four (two EURO-0 and two EURO-1) four-stroke engine, in-use scooters with displacement of 150 cc, which were not equipped with catalytic converters. Non-catalysed motorcycles still represent a large proportion of circulating two-wheelers in Italy and, possibly, also in other countries. Tests were performed on a dynamometer bench, using the ECE-40 test cycle procedure. Particulate matter into the exhaust emissions was collected both during the "hot" phase of the ECE-40 driving cycle and including the first two elementary cycles of engine warming-up heating (whole cycle). Fourteen PAHs were quantified and total PAH emission factors (Sigma PAH) ranged from 7 to 169 microg km(-1). Expressed in benzo(a)pyrene equivalent (BaP(eq)), emission factors ranged from 0.6 to 18 microg km(-1). Results from the tested scooters show that despite their small engine size, non-catalysed motorcycles can emit amounts of particulate PAHs that can be comparable or even higher than emissions reported elsewhere from gasoline- and diesel-powered passenger cars and light- and heavy-duty vehicles. In countries where a large number of non-catalysed motorcycles are circulating, PAH emissions in urban areas from this class of vehicles might be of the same order of magnitude of emissions from diesel passenger cars.