Distribution of selected heavy metals in fluvial sediments of the coal mining region of Baixo Jacuí, RS, Brazil

The geochemical distributions of Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were investigated to provide information about the mobility and availability of these elements in polluted sediments from the Baixo Jacui region, southern Brazil. Sediment samples were collected at eight sites in the Conde stream, near coal mining and waste disposal areas, and in the Jacui river, downstream from industrial activities. Total extraction results showed higher metals concentration at some sites, when compared to background values, as well as indicated by the calculated enrichment factor and geoaccumulation index. However, the results were insufficient to establish the existence of anthropogenic contribution to the studied area. The contamination was better evaluated by the sequential extraction. The geochemical distribution in the sediments of the Jacui river revealed the presence of high concentrations of Cr and Cu in the oxidizable fraction, in response to effluent discharge from coal fired power stations and a steel plant. Higher percentages of the available fraction were verified in the Conde stream for the elements Cu, Fe, Ni, Pb, and Zn, indicating the sediment contamination by coal-related activities.