Spatial patterns and environmental risk associated to trace metals in sediments from Sepetiba bay, Rio de Janeiro, Brazil

Abstract

The sediment quality of Sepetiba bay is affected by trace metals from input of many human activities. The environmental risk index showed high values due to trace metals pollution in the inner part of the bay, but also along Marambaia sandbar area. Cd and Zn are of critical concern for Sepetiba bay sediments management, due to their high concentrations and potential toxicity to aquatic organisms. However, copper stands out in hot spots. Marambaia bay sedimentation rates enhancement was concurrently with the introduction of Paraíba do Sul-Guandu rivers diversion system. Higher amounts of Cd and Zn were found in the inner part of the bay since 1960’s, concurrently with the Ingá metallurgical Cia. establishment. Mn oxy-hydroxides compose the main phase in the sediments fractionation, which is considered an important scavenger for trace metal in the region. A systematic and recurrently monitoring program has to be implemented, since Zn and Cd high concentrations from Ingá wastes can be masking other potential sources. Therefore, other contaminants must be monitored, such as Cu, Pb and Cr. Especially due to the growth of industrial and harbor activities in Sepetiba bay basin, other point and non-point pollution sources for the system are expected.