Cabuçu-Piraquê River, a tributary of Sepetiba Bay (Rio de Janeiro State, Brazil), has a history of pollution for decades, but without a systematic study of origin and fate of trace elements such as cadmium and zinc, in its environmental compartments. The bioaccumulation of these elements can cause serious damage to the biota of mangroves in its estuary, and to human consumers of local fisheries. In this study, it was evaluated the current state of contamination of water and sediment from that

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... ver, as well as the occurrence of accumulation of these metals in the estuary´s sediment fraction brought by the bay waters during high tides. Concentrations of cadmium and zinc above those considered safe by Brazilian law were found both in the fine fraction (< 63 µm) of sediment, averages of 4.4 and 1232 mg/kg, respectively, and at high tide waters, 0.08 and 0.24 mg/L, respectively. Both metals were found only in the most bioavailable operational fractions of waters, while sediment average values of 96 % were found for Cd, and 98 % for Zn at same most bioavailable fractions. From the concentrations of these metals in water from the saline wedge generated by the bay, it was possible to infer such an influx into the estuary from the material present in the bay waters, and this transport process may be shipping a major contributor to contamination of the local mangroves.