A comparative study of heavy metal concentration and distribution in deposited street dusts in a large and a small urban area: Birmingham and Coventry, West Midlands, UK S. Charlesworth a, * , M. Everett a , R. McCarthy a , A. Ordo ´n ˜ez b , E. de Miguel c a Department of Geography, Coventry University, Priory Street, Coventry, CV5 1FB UK b Departamento de Explotacio ´n y Prospeccio ´n de Minas, E.T.S.I.M.O., Universidad de Oviedo, Oviedo, Spain c Departamento de Ingenierı ´a Quı ´mica y Combustibles, E.T.S.I.M.M., Universidad Polite ´cnica de Madrid, Madrid, Spain Received 25 June 2002; accepted 13 January 2003 Abstract Results are presented from a study of the distribution of heavy metals in street dusts of two cities in Midland England. The first (Birmingham) is a large urban area (population of 2.3 million), the second, Coventry, a small one (population of 0.3 million). Several trends were identified from Birmingham: higher concentrations were located near industrial areas in the northwest of the city and within the ring road. However, lower concentrations were found to the southwest in areas of mainly residential properties and parks. High values were also identified in association with junctions controlled by traffic lights where vehicles were likely to stop regularly. This last trend was further investigated in Coventry, where it was found that concentrations of heavy metals at junctions controlled by traffic signals and by pedestrian- controlled pelican lights (Mounted Pelican Controller, MPCs) were lower than those found in Birmingham, apart from Ni. D 2003 Elsevier Science Ltd. All rights reserved. Keywords: Comparative study; Heavy metal concentration; Street dusts 1. Introduction Interest in the levels of contaminants associated with street dusts has risen in the last decades, particularly in light of the impact of high blood–Pb levels in children living in urban areas and the likelihood of this being caused by inadvertent hand–mouth contamination caused while the child plays in a city street (Akhter and Madany, 1993). Many studies throughout the world have identified the sources of these contaminants in street dust as those associated with vehicular traffic, industrial and residential areas as well as weathering of building facades, and have in fact recognised street dust as a significant pollution source itself (Akhter and Madany, 1993). Table 1 summarises the concentrations of heavy metals published in some of these studies showing the range of values found globally. Various trends can be identified on examination of results from street dust studies throughout the world: 1. Spatially, the total concentrations of heavy metals have been related to industrial and residential areas (Davies et al., 1987; Kim et al., 1998; Dong et al., 1984) as well as traffic movements, numbers of vehicles and their speed (Day et al., 1975; Leharne et al., 1992; Ellis and Revitt, 1982; Hamilton et al., 1984). 2. Comparison of the populations of the cities in Table 1 with heavy metal concentrations is summarised in Table 2. In general, the larger the population, the higher the heavy metal concentration in street dust; this is partic- ularly true of Cd and Pb. The correlation coefficient for Ni is low, but may be a reflection of the few studies (6) which examined this element. 3. Sequential extractions have identified Cd as the most bioavailable element as it has the highest percentages bound to operationally defined exchangeable sites and carbonates. Zn and Pb are mainly associated with carbonates and then Fe/Mn oxides, but not the exchange- able fraction. The vast proportion of Cu is bound to 0160-4120/03/$ - see front matter D 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0160-4120(03)00015-1 * Corresponding author. Tel.: +44-24-76-888498; fax: +44-24-76- 888447. E-mail address: s.charlesworth@coventry.ac.uk (S. Charlesworth). www.elsevier.com/locate/envint Environment International 29 (2003) 563 – 573