title: Metal particle emissions in the exhaust stream of diesel engines: an electron microscope study.
abstract: Scanning electron microscopy and transmission electron microscopy were applied to investigate the morphology, mode of occurrence and chemical composition of metal particles (diesel ash) in the exhaust stream of a small truck outfitted with a typical after-treatment system (a diesel oxidation catalyst (DOC) and a downstream diesel particulate filter (DPF)). Ash consists of Ca-Zn-P-Mg-S-Na-Al-K-phases (lube-oil related), Fe, Cr, Ni, Sn, Pb, Sn (engine wear), and Pd (DOC coating). Soot agglomerates of variable sizes (<0.5-5 μm) are abundant upstream of the DPF and are ash-free or contain notably little attached ash. Post-DPF soot agglomerates are very few, typically large (>1-5 μm, exceptionally 13 μm), rarely <0.5 μm, and contain abundant ash carried mostly from inside the DPF. The ash that reaches the atmosphere also occurs as separate aggregates ca. 0.2-2 μm in size consisting of sintered primary phases, ca. 20-400 nm large. Insoluble particles of these sizes may harm the respiratory and cardiovascular systems. The DPF probably promotes breakout of large soot agglomerates (mostly ash-bearing) by favoring sintering. Noble metals detached from the DOC coating may reach the ambient air. Finally, very few agglomerates of Fe-oxide nanoparticles form newly from engine wear and escape into the atmosphere.
authors.affiliation: Empa Material Science and Technology, Laboratory of Internal Combustion Engines , Ueberlandstrasse 129, CH-8600, Dübendorf, Switzerland.
authors.forename: Anthi
authors.initials: A
authors.lastname: Liati
authors.forename: Daniel
authors.initials: D
authors.lastname: Schreiber
authors.forename: Panayotis
authors.initials: P
authors.lastname: Dimopoulos Eggenschwiler
authors.forename: Yadira
authors.initials: Y
authors.lastname: Arroyo Rojas Dasilva
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry; D005374:Filtration; D008670:Metals / Q000032:analysis*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D018986:Motor Vehicles; D053758:Nanoparticles / Q000648:ultrastructure; D010316:Particle Size; D052638:Particulate Matter / Q000737:chemistry*; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D005290:Ferric Compounds; D008670:Metals; D052638:Particulate Matter; D001335:Vehicle Emissions; C000499:ferric oxide