Elemental evaluation of urban road dirt in tropical, arid and maritime climates

Interest is in vehicular trace elemental contributions to the environment, evaluated via analysis of road dirt. Results from SEM/EDX, ICP-MS and ICP-OES are compared for a wide range of elements. ICP-OES and ICPMS provide absolute quantification while SEM/EDX has provided weight % assessments. Roadside dirt has been sampled along busy campus roads of universities/research centres in Guildford, Riyadh, Kuwait City, Doha and Kuala Lumpur, satisfying interest in climatic influences as well as vehicle engine size (Gulf non-commercial vehicle engine capacities tending to be greater than those in the UK or Malaysia). A total of 100 street dust samples have been analyzed, elemental concentrations being reported for Mg, Al, Ti, Mn, Fe, Co, Zr, Mo, Ba, Tl, V, Rd, Pb, Cu, Zn, Ni, Cr, Cd, As, Hg and Au. For all five urban centres, Al, Fe, Mg, and Si values were found to be well above background while concentrations of Ti, Cr and Ba were lower than values reported by others. Au and Ag from catalytic convertors were found in some centres, albeit at very low concentrations and with particle sizes of the order of 0.5 µm. The various techniques offer complementary information on vehicular emission elemental concentrations in urban environments.