Lead and other heavy metal pollution of the urban environment

Abstract

Environmental pollution by lead from traffic sources and lead industries (a secondary lead smelter and a battery factory) have been investigated. Roadway gutter dusts were gathered from 9 locations, representing 5 commercial, 4 residential and 3 industrial classes of dust, respectively. Dusts were analysed for Pb, Zn, Cu, Ni, Cr, Fe, Mn, Ba, V, Rb and Y by X-ray Fluorescence Spectrometry, and As by Atomic Absorption Spectrometry. The average lead level in a total of 91 dust samples was 2520±1791 ppm, which is amongst the highest levels reported in studies of urban roadway dust. Lead levels were obviously influenced by traffic density with the range of levels in commercial areas generally being the highest. Concentrations of Zn, Cu, Cr, were also elevated above background levels. The levels of Cu also appear to be influenced by traffic density. A search for the sources of metals in roadway dust showed that motor vehicles appear likely to be the major contributor of the metals Pb, Zn, Cu, Ni, Cr and Fe. The variation of metal concentrations with dust particle sizes was also determined, results obtained proved informative in tracing the origins of metals. Detailed sampling and analysis of lead in soils and dusts, in the immediate vicinity of a lead smelter, showed that elevation of lead in soils and in dusts was apparent up to a distance of about 40 m and 70 m respectively, from the smelter source. Apart from lead, arsenic and antimony were also identified as emitted from both the smelter and the battery factory, in line with reports in other studies. Two dust samples from the battery factory, and 1 dust sample from the smelter, were identified for the form of lead compounds present, by X-ray Diffraction and Electron Microprobe techniques. PbSO4 was identified as the most probable crystalline compound of lead in all the dust fractions examined. Despite the high concentration of lead in some dust fractions, the amount of crystalline PbSO4 present was estimated to be less than 5%. α-Quartz and feldspar were found to be obvious major components since the dusts examined were essentially soil material contaminated by lead. The majority of the lead was present in association with soil material, which would preclude analysis by X-ray Diffraction.