Heavy metals in stream sediments from copper and gold mining areas in southern Brazil

This work is part of a research effort which is intended to identify natural and anthropogenic sources for metal contamination in gold and copper mining areas of the Camaqua River Basin, located in the shield region of the Rio Grande do Sul state. This particular study area is located in the upper Camaqua River Basin, where gold, copper and marble occurs. Stream bed sediments were collected during four sampling periods, between 1992 and 1994. Total Fe, Mn, Cu, Zn, Pb and Hg concentrations as well as TOC contents were determined in the silt-clay fraction of all collected samples. Sequential extractions were performed in some selected samples to evaluate geochemical phase associations and potential metal mobilities. A general increase in metal concentrations was observed in more recent sampling periods for Mn, Fe and Cu, especially in the copper mining area. Two groups of metals, Cu-Fe and Hg-Pb-Zn-Mn, presented some similarities in spatial distributions, but exhibited different geochemic behaviors in the gold and copper mining areas.