Environmental pollution by heavy metals in the Sao Joao River basin, southern Brazil

Environmental pollution tends to reduce the quality of water sources around the world. Thus, there is a clear need for strategic assessments of conditions that negatively affect river basins. The Sao Joao River basin is located in a strategic conservation area due to the abounding water resources and biodiversity, but is strongly affected by anthropic activity. In this study, eight metals were evaluated (Cu, Mn, Fe, Zn, Cr, Co, Cd and Pb) in sediment and water from ten different points in the Sao Joao water basin. The Sao Joao basin pollution was evaluated through the geoaccumulation index (Igeo), ecological risk potential (ERP) and degree of pollution (Dp). The most toxic metals found in sediments were Cr (3.1-10.7), Cd (2.1-5.5) and Pb (5.0-28.1) in mu g g(-1). In the water samples, the most toxic metals were Cr (3.7-33.2), Cd (6.3-14.2) and Pb (5.0-57.5) in lg L-1. The Igeo presented indices between 2 and 3 in 80% of the samples, indicating significant pollution in the sediment. In 40% of the points sampled, the ERP values indicated severe risk for the ecosystem. In 30% of the water samples, the Dp values were over 40, indicating the highest pollution level. The results reveal that the use of land and water in the Sao Joao water basin without proper care might represent considerably high ecological and sanitary risk.