EMISSIONS OF TRACE-ELEMENTS FROM MOTOR-VEHICLES - POTENTIAL MARKER ELEMENTS AND SOURCE COMPOSITION PROFILE

The phasing-out of leaded gasoline has rapidly reduced the value of Pb, the traditional marker element for emissions from gasoline-powered vehicles for receptor-model studies. Also, the emission characteristics have changed considerably due to factors such as modern catalytic converters and changes in motor oil additives. These changes have made current motor-vehicle source composition profiles questionable. In this study we attempted to identify marker elements and to develop a new source composition profile for motor vehicle emissions. To accomplish this, we collected numerous samples directly from motor vehicles and in locations that are heavily influenced by these emissions. All the samples were analysed for trace element concentrations by instrumental Neutron Activation Analysis (INAA). Rare earth elements (REEs) are used in catalytic supports and have been suggested as possible marker elements for motor vehicle emissions. Our results show that considerable amounts of Zn, Br, and Sb are emitted by motor vehicles; their combined emissions are much larger than the sum of the REEs. Also Sb, Zn, and Br have smaller coarse/fine particle ratios (C/F ratios) than do the REEs. It is suggested that Sb, Br, and Zn are potential marker elements. Furthermore, based on our analysis, a partial elemental composition library for motor vehicle emissions is updated and a brief discussion of the origins of elemental constituents from motor vehicle exhausts is given.