Assessment of diffuse pollution associated with metals in urban sediments using the geoaccumulation index (Igeo)

Purpose This study investigated the behavior of cadmium (Cd), lead (Pb), nickel (Ni), and zinc (Zn) in urban sediments collected in commercial, residential, and industrial areas of the city of Porto Alegre, Brazil, and evaluated different degrees of pollution in this urban subdrainage basin through the use of the geoaccumulation index (I-geo). Materials and methods Concentrations of Cd, Ni, Pb, and Zn were analyzed using acid digestion (EPA method 3050) in fractions <63 mu m in 20 composite samples of urban sediment collected using a portable vacuum in 20 different sampling points on roads from three areas with diverse use: commercial, industrial, and residential. Results and discussion The values of I-geo were commercial area (3.35, Zn; 3.76, Cd; 3.60, Ni; 2.63, Pb) > residential area (3.34, Zn; 3.36, Cd; 2.94, Ni; 1.46, Pb) > industrial area (2.74, Zn; 1.78, Cd; 3.01, Ni; 1.45, Pb), indicating that the sediment was highly contaminated in the case of Zn and Ni, while for Cd, it was moderately to highly contaminated, and for Pb, it was moderately contaminated. The pollution is associated with traffic flow in all areas. Conclusions Research should be increased to make urban systems more sustainable, reducing their pollution potential and minimizing the delivery of potentially polluting particles into freshwater bodies. The I-geo allows for the determination of a simple index of diffuse pollution state associated with urban sediments.