Species analysis of automotive carbon particles: Application of XPS for integral analysis of filter samples

 In the discussion of possible toxic effects of carbon particle emissions from automotive sources the question about the origin of the material is of relevance. Besides the emissions of Diesel soot (DS) a second source of debris from tire abrasion (TD) has the potential to contribute significantly to the carbon particle emissions. The discrimination between these chemically different species is complicated by the unavoidable presence of molecular carbon species from general sources, from fuel components and from polycyclic aromatic hydrocarbons (PAH) on the filter surface deposits from imission tests. Based on the different surface reactivity of DS and TD, a quantitative data analysis procedure using the X-ray photoelectron spectroscopy (XPS) carbon 1s profile is suggested, which gives an estimate of the fraction of DS in the total carbon present. The difference to 100% is the sum of TD and molecular carbon which constitutes its dominant contribution. The method agrees semi-quantitatively with traditional chemical analysis of the elemental carbon fraction on the filters. Several independent chemical tests are provided for the internal consistency of the analysis method which is based upon the use of reference spectra from pure TD. The application of a simplified analytical equipment for large numbers of samples is discussed. Received : 26 January 1996/Revised: 23 April 1996/Accepted : 29 April 1996