Direct determination of Platinum Group Element (PGE) emissions in passenger cars equipped with Diesel Particulate Filters (DPF).

Over the few last years there has been an increasing concern about the possible drawbacks in the use of the automobile catalytic converters; in fact, the ever increasing exploitation of these devices has led to an increasingly widespread emission of PGEs into the environment as a consequence of mechanical and thermal abrasion of the catalysts. It is believed that PGEs are released by the catalytic converters in a particulate form, mainly in the (0) oxidation state or as oxides, and it has been shown that they undergo environmental transformations into more reactive species which may be bio-available. For this reason more specific research is necessary to estimate the real amount of PGEs released into the environment by catalytic converters. In this presentation the applied methodology to determine PGE emission factors through direct measurements at the end of a catalytic converter of a diesel powered vehicle and the results obtained are described. The behaviour of different post-treatment devices was checked in order to have a wider outlook. Both new and aged catalytic converters fitted with particulate traps were monitored. The samples were analysed by an analytical methodology based on the use of the ICP-MS technique combined with a sensitivity enhancing sample introduction system and cation exchange cartridges. The final results show that most of the emitted PGEs are in the particulate phase and characterised by a composition similar to the PGEs originally deposited on catalyst substrate. Moreover, an important reduction of these emissions was observed in the presence of a particulate filter in the exhaust line.