Trace metal contamination in mangrove sediments, Guanabara Bay, Rio de Janeiro, Brazil

Abstract

The Guanabara Bay in Rio de Janeiro has undergone profound alterations of its natural environmental conditions. Metal concentration increase in sediments has been reported to be among these alterations. Trace-metal contamination and availability were studied in sediments of 3 mangrove areas of the bay. Cd, Zn, Pb, Ni, Cu and Al concentrations were determined in segments of sediment cores, after treatment with 1 mol L-1 HCl and with concentrated HNO 3. Fe and Mn were determined in the leach with HNO3. Concentrations were low in comparison to those reported for Guanabara Bay and Cd showed up to 90% recovery in the HCl extract. Sediments found to be oxic to suboxic showed AVS concentrations in range of 0.07 (bottom) to 18.79 μmol g-1(sub-surface) indicating heterogeneity and apparent disequilibrium. Fe and Mn oxides, carbonates and organic matter may be the most important phases controlling metal availability and distribution. ©2007 Sociedade Brasileira de Química.