Organic-rich nanoparticles (diameter: 10–30 nm) in diesel exhaust: Fuel and oil contribution based on chemical composition

The size distribution of particle number concentrations and comprehensive chemical composition (elemental and organic carbon, elements, ions, and organic compounds) by particle size (diameter: 0.010–10 μm) were measured under no-load and transient conditions in the exhaust from an 8-L diesel engine with no exhaust after-treatment system and from a 3-L diesel vehicle equipped with an oxidation catalyst. High concentrations of nuclei-mode particles were emitted from the 8-L engine under no-load condition (8L-NoLoad), even when low-sulfur (8 ppm) fuel was used, but no nuclei-mode particles were emitted from the 3-L vehicle. Organic carbon accounted for a major part (79–80%) of the measured components of the nanoparticles (diameter: 10–32 nm) under 8L-NoLoad, but elemental carbon accounted for only 8–15%; elements and ions including sulfate accounted for only small percentages. The mass chromatogram ( m/ z 85) patterns obtained by gas chromatography–mass spectrometry of the nanoparticles were similar to those for lubricating oil, and the peak profiles for hopanes were equivalent to those in oil. The 17α(H),21β(H)-hopane concentrations per particle mass were higher in smaller particles. The elements concentrated in oil were also concentrated in the nanoparticles. These results suggest that not sulfate and fuel but organics derived from oil were the primary components of the nanoparticles under 8L-NoLoad. From the 17α(H),21β(H)-hopane concentrations, the oil contribution to the sum of measured components in the nanoparticles under 8L-NoLoad was estimated at 79–92%. Comparable oil contributions were estimated from Ca and Zn concentrations. ► Comprehensive chemical composition of diesel exhaust nanoparticles was measured. ► Organics were dominant for the nanoparticles under nanoparticle-dominated condition. ► Oil contribution in the organic-rich nanoparticles was estimated at 79–92%.