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Martínez and Poleto 1 J U E E Journal of Urban and Environmental Engineering, v.4, n.1, p.1-8 ISSN 1982-3932 doi: 10.4090/juee.2010.v4n1.001008 Journal of Urban and Environmental Engineering www.journal-uee.org LEAD DISTRIBUTION BY URBAN SEDIMENTS ON IMPERMEABLE AREAS OF PORTO ALEGRE – RS, BRAZIL Leidy L.G. Martínez 1∗ and Cristiano Poleto 2 1 Hidraulic Research Institute, Federal University of Rio Grande do Sul, Brazil 2 State University of Maringá, Brazil Received 23 April 2009; received in revised form 15 June 2010; accepted 18 June 2010 Abstract: Keywords: Heavy metals, like lead (Pb), are subproducts of industrial activities; however, in recent years, studies have shown that even in non-industrial areas, elevated concentrations of this element have been found. In this study, Pb concentrations were measured in 20 composite samples of urban sediments collected in an urban watershed of 4.85 km² with three types of soil use (commercial/residential, commercial and industrial) in the city of Porto Alegre, RS, Brazil. Concentrations were determined by acid digestion (EPA 3050) of the 209 µm, 150 µm, 90 µm, 63 µm and 45 µm fractions followed by atomic emission spectrophotometry with inductively coupled plasma. Average values of 178.1 µg.g -1 (± 332); 226.5 µg.g -1 (± 500); 245.2 µg.g -1 (± 454.1); 272.4 µg.g -1 (± 497.3) and 251.5 µg.g -1 (± 322.6) were obtained in the 209, 150, 90, 63 and 45 µm fractions, respectively. Concentrations of the metals studied were interpolated and represented geographically using Idrisi © Andes. Results show that the greatest concentrations are located in the commercial part of the study area, characterized as presenting high vehicle flow most of the day, with this being considered a potential source of lead. All concentrations were above that of the local background. Studies of this type are important because they make the establishment of control targets possible within sustainable management of water resources, allowing inferences regarding future pollution scenarios of local water resources. Urban sediment; diffuse pollution; GIS; lead © 2010 Journal of Urban and Environmental Engineering (JUEE). All rights reserved. ∗ Correspondence to: Leidy L.G. Martínez, Tel.: + 55 51 3308 6686. E-mail: luxgm@yahoo.es Journal of Urban and Environmental Engineering (JUEE), v.4, n.1, p.1-8, 2010
Martínez and Poleto 2 INTRODUCTION Most South American cities present accelerated growth trends; however, they are disorganized, generating negative impacts especially on bodies of water (Poleto et al,. 2009a; Deletic et al,. 1997), principally due to the increase of impermeable surfaces like roadways, roofs, parking lots, among other things, which reduce the rate of infiltration and increase surface runoff, thus increasing transport of urban sediment and pollutant loads to watercourses (Poleto et al., 2009b; Taylor 2007; Charlesworth et al., 2003; Deletic et al., 1997). Urban drainage networks are responsible for conveying these loads and it is now known that they constitute important sources of degradation of rivers, lakes and estuaries Horowitz (2009), (Deletic et al., 1997). Sediments in urban areas are submitted to man-made alterations from different sources, as for example, the input of organic matter coming from discarding sewage in a clandestine manner, in the same way as particles of human origin present in large quantities in urban environments, such as glass particles, metallic particles, residues from industrial processes and civil construction, which present chemical and mineralogical properties different from sediment particles from natural sources, which results in these sediments interacting in a different way within the environment (Poleto & Martínez, 2009); Taylor (2007). Sediments deposited in roadways have become, through time, an important means for determining the human contribution of pollutants, especially that of heavy metals. The ubiquitous nature of road deposited sediments, their ease of sampling, their strong association with automobile emissions, and their relationship with nonpoint source pollution make them a valuable archive of environmental information (Sutherland 2003). More precisely, one of the chemical characteristics of vital importance in the study of urban sediments is adsorption of heavy metals. Banerjee (2003) defines the behavior of heavy metals in terms of the most common different solid phases found in urban sediments in Table 1. Affinity of heavy metals by sediments is strongly influenced by particle size (Deletic et al., 1997; Charlesworth et al., 2003; Sutherland, 2003; Taylor, 2007; Poleto et al., 2009a). There is sufficient evidence that shows the fact that sediments are enriched with heavy metals, above all in the fine particle fraction. In a similar way to sediments in other environments, increase in the pollutant load in finer sized particles is generally associated with the increase of surface area in smaller sized particles, providing greater space for adsorption of metals in clay minerals or in organic matter present in sediment particles. Understanding that heavy metal loads are heterogeneously distributed is important in the formulation of pollution management and control strategies (Horowitz, 2009; Poleto et al., 2009b; Taylor, 2007). Fergusson & Ryan (1984) studied Table 1. Affinity of heavy metals in sediments Solid phase fraction Exchangeable Carbonate Fe-Mn oxide bonding Organic matter Residual Adapted from: Banerjee (2003). Affinity of heavy metal Cd > Pb > N i> Zn > Cu > Cr Cd > Zn > Pb > Ni > Cu > Cr Zn > Pb > Ni = Cu > Cd > Cr Cu > Pb > Zn > Ni > Cd > Cr Cr > Ni > Cu > Cd > Pb > Zn the composition of particles deposited in urban areas, specifically particle size and the sediment source; they found that many of the elements analyzed increased with reduction in particle size, a result corroborated by Al-Rajhi et al. (1996). In urban environments, heavy metals are part of our daily activities and many of them enter in the urban environment as subproducts of economic activities which are considered typical in urbanizing watersheds (Poleto & Charlesworth, 2010; Poleto et al., 2009a; Poleto & Martínez 2009; Irvine et al., 2009); in the case of lead, it frequently appears as a subproduct from petroleum and coal combustion; tire, oil, paint and welded part residues (Horowitz, 2009; Poleto & Merten, 2008; Charlesworth & Lees 1999). Lead concentration values are variable and depend in large part on surrounding local conditions; Sutherland (2003) found that 51% (221 µg.g -1 ) of the lead load present in sediments deposited in urban roadways in Hawaii were found in the < 63 µm fraction; Robertson et al. (2003) found concentrations of 354 µg.g -1 within the city of Manchester (United Kingdom); Charlesworth et al. (2003) found average values of 48 and 47.1 µg.g -1 in the cities of Birmigham and Coventry (United Kingdom), respectively; Irvine et al. (2009) reported values of 276 µg.g -1 in the city of Hamilton, Ontario (Canada); an average value of 230.52 µg.g -1 with a maximum of 3060 µg.g -1 were found by Yongming et al. (2006) in the province of Xi’an in China; McAlister et al. (2005) reported concentrations from 200 to 700 µg.g -1 in areas with diverse soil uses in the city of Rio de Janeiro (Brazil) and Poleto et al. (2009) found concentrations from 16 to 110 µg.g -1 in 20 cities in the South of Brazil. Sediments deposited in roadways are commonly associated with risks to the environment and to human health, mainly in children (Taylor, 2007; Charlesworth et al., 2003; Al-Rajhi et al., 1996). Environmental and health effects initially depend on the mobility and availability of the elements, and the mobility and availability in terms of their chemical speciation and fractionation within or on particles (Banerjee, 2003). In the case of lead, there is evidence that indicates that exposure to this metal (inhalation or through consumption of contaminated foods) can trigger problems in the central nervous system, as well as having carcinogenic effects (Wang et al., 2005). Journal of Urban and Environmental Engineering (JUEE), v.4, n.1, p.1-8, 2010
Page 2 and 3: EDITORIAL TEAM Editors Celso August
Page 6 and 7: Martínez and Poleto 3 In the prese
Page 8 and 9: Martínez and Poleto 5 Table 2 Desc
Page 10 and 11: Martínez and Poleto 7 CONCLUSIONS
Page 12 and 13: Akpinar and Akpinar 9 J U E E Journ
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