LEAD DISTRIBUTION BY URBAN SEDIMENTS ON IMPERMEABLE AREAS OF PORTO ALEGRE – RS, BRAZIL

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.