Trace and minor element characterization of diesel soot

Summary

Concentrations of 20 trace and minor components, such as metals, nitrogen and sulphur, were determined in representative diesel soot samples corresponding to various driving patterns of an old and a new type of Mercedes-Benz diesel engine for passenger cars. The samples were analysed by instrumental neutron activation analysis, and after decomposition, by flame and graphite furnace atomic absorption spectrometry. The content of sulphur was determined by a method based on the formation of hydrogen sulphide and precipitation micro-titrimetry. The concentrations of the elements Au, La, Sb, Sc, and V were at the sub-μg/g level; As, Ba, Cd, Co, Cr, Mn, Ni, and Se were at the lower μg/g level; and Ca, Cu, Fe, N, Na, Pb, S, and Zn ranged from the upper μg/g to lower percent levels. The emission of several elements was likely the result of different factors such as utilization of organometallic additives (Ca, Na, Zn) in diesel fuel or lubrication oil, contamination of diesel fuel by alkyllead compounds, wear and corrosion of the engine and exhaust system parts. The concentration of elemental components in diesel soot, generally, varied with operating conditions, which affected fuel and oil consumption, combustion efficiency (soot production), and mechanical strain.