Technical note: Emission factors, chemical composition, and morphology of particles emitted from Euro 5 diesel and gasoline light-duty vehicles during transient cycles

Abstract

Changes in engine technologies and aftertreatment devices can profoundly alter the chemical composition of the emitted pollutants. To investigate these effects, we characterized the emitted particles chemical composition of three diesel and four gasoline Euro 5 light-duty vehicles tested at a chassis dynamometer facility. The dominant emitted species was black carbon (BC) with emission factors (EFs) varying from 0.2 to 7.1 mg km1 for direct-injection gasoline (GDI) vehicles, from 0.02 to 0.14 mg km1 for port fuel injection (PFI) vehicles, and 0.003 to 0.9 mg km1 for diesel vehicles. The organic matter (OM) EFs varied from 5 to 103 ug km1 for GDI gasoline vehicles, from 1 to 8 ug km1 for PFI vehicles, and between 0.15 and 65 ug km1 for the diesel vehicles. The first minutes of coldstart cycles contributed the largest PM fraction including BC, OM, and polycyclic aromatic hydrocarbons (PAHs). Using a high-resolution time-of-flight mass spectrometer (HR-ToF-AMS), we identified more than 40 PAHs in both diesel and gasoline exhaust particles including methylated, nitro, oxygenated, and amino PAHs. Particle-bound PAHs were 4 times higher for GDI than for PFI vehicles. For two of the three diesel vehicles the PAH emissions were below the detection limit, but for one, which presented an after-Treatment device failure, the average PAHs EF was 2.04 ug km1, similar to the GDI vehicle s values.