Evaluation of heavy metal levels in surface water and sediments of Monte Alegre Stream and tributaries, Ribeirão Preto, SP, Brazil

The present study analyzed the levels of heavy metals in surface water and sediment of Monte Alegre stream and its tributaries, a watercourse located in an area under strong anthropogenic impacts. Results were compared with data from a study published in 2004. To evaluate the levels of Cd, Cr, Cu, Mn, Pb and Zn, 18 samples of surface water and 9 of sediment were collected. Metal levels were measured by atomic absorption spectrophotometry. The average concentrations of Zn and Pb in surface water samples exceeded the maximum limits for rivers of class 1, but not for rivers of class 3 according to Resolution 357/2005 of the National Environmental Council (CONAMA). Mn average concentrations did not present values higher than the maximum limits for rivers of class 1 and 3, but in some points it exceeded the maximum limits for rivers of class 1. The average concentration of Mn, Cd and Pb were higher in published study in 2004 while Zn was higher in 2007. In sediment samples, Cu and Zn showed average concentrations higher than the limits set by the Netherlands and by Resolution 344/2004 of the National Environmental Council.