Assessment of metal concentration in the Billings Reservoir sediments, São Paulo State, Southeastern Brazil

Four approaches were applied to evaluate the metal contamination in 47 sediment samples (< 63 µm fraction) collected at 13 fishing points of the Billings Reservoir: sediment quality guidelines (SQGs), geoaccumulation index (I Geo), metal pollution index (MPI) and statistical analyses. Only Fe and Co concentrations seemed to be associated with crustal material or natural weathering processes, while Al, Cd, Cr, Cu, Hg, Mn, Ni, Pb and Zn showed increases in their concentrations, which seemed to be associated with anthropogenic sources. MPI identified the most critical sites in relation to the total metal accumulation while I Geo identified the specific metal accumulation for each site. Analysis of variance (ANOVA) and box plot method were performed to evaluate seasonal effects on the metal levels. Only box plot suggested a slight increase in Hg and Pb contamination during heavy rainy periods and also indicated high concentrations of Cu and Zn in one of the analyzed point, with incidence of outliers and extreme values. Thus, an environmental policy in order to reduce these metal contaminations must be adopted.