Organic profiles of particulate matter emissions from a Euro VI diesel city bus

To perform a detailed organic speciation, particulate matter emitted by a Euro VI diesel city bus was collected combining chassis dynamometer and on-road testing. Dynamometer exhaust emission tests were performed following the Braunschweig and the world harmonised vehicle cycle (WHVC). On-road testing was done on two routes representing typical city bus operation and an additional circuit following the in-service conformity (ISC) requirements. Amongst other constituents, exhaust particles included polycyclic aromatic hydrocarbons (PAHs), alkyl-PAHs, alcohols, various types of acids, glycerol derivatives, and glycols. Particulate matter mass fractions of these compounds were much higher in samples from on-road driving tests compared to chassis dynamometer cycles. Retene and 5-ring PAHs were the dominant compounds within this family. Alkyl-naphthalenes and alkyl-phenanthrenes were also detected. On average, 20% of the analysed PAHs were found to contribute to the carcinogenic potency of the particulate material. For many compounds, in the dynamometer tests, the highest particulate mass fractions were obtained for the WHVC with hot start. Compounds from fuel additives (e.g. levulinic acid), components of the cooling system fluids (e.g. ethylene glycols), by-products of after-treatment technologies (isocyanic acid) and antioxidants leached from polymeric materials (e.g. oxidised Irgafos® 168) were observed in the exhaust particles. The detection of constituents such as monoglycerides and hydroxytoluene suggests the use of diesel/biodiesel blends by bus drivers.