Nanoparticles at internal combustion engines exhaust: effect on urban area

The role of Spark Ignition (SI) and Diesel engines as nanoparticles sources in urban area was investigated. Detection, sizing and counting of particles were realized at the exhaust of a Port Fuel Injection Spark Ignition (PFI SI) engine equipped with a Three-Way Catalyst (TWC) and a Unijet Common Rail (CR) Diesel engine equipped first with an Oxidation Catalyst (OC) and then with a Catalyzed Diesel Particulate Filter (CDPF). Engine operating conditions in high road traffic were considered. Electrical Low Pressure Impactor (ELPI) was used as real-time measurements device for particle size distribution in the range from 7 nm up to 10000 nm. Broadband UV–Visible Extinction and Scattering Spectroscopy (BUVESS) allowed investigating the chemical and physical nature of emitted particles. It was observed that the major contribution to particulate mass is due to Diesel engine equipped with the OC, the other engines contribute only in terms of number concentration. Diesel engine size distributions show a nucleation mode centered around 20-30 nm and an accumulation one centered on 70 nm. The first one dominates downstream the CDPF meanwhile the second one is stronger downstream the OC. At the exhaust of PFI SI engine a large nucleation mode centered around 7 nm is present.BUVESS measurements show that the Diesel particles consisted of soot and that the gasoline ones are due to organic compounds.