Assessment of bioavailability and potential toxicity of Cu, Zn and Pb, a case study in Jurujuba Sound, Rio de Janeiro, Brazil

•Fractionation of Zn, Pb and Cu in sediments from Jurujuba Sound was studied.•Principal component analysis and Igeo were used to evaluate data.•Trophic state was determined based on the content of biopolymeric carbon.•Sediments extremely enriched with organic matter played a fundamental role in the retention of trace metals.•Zn can be considered the most threatening trace element to the local biota.

Potential toxicity of sedimentary Cu, Zn and Pb were evaluated based on their fractionation at the inner part of Jurujuba, a small sound at the eastern margin of Guanabara Bay, Rio de Janeiro. Biogeochemical composition revealed an environment extremely enriched with anthropic organic matter and characterized as a detrital heterotrophic system. The fractionation analysis showed that Pb exhibited more affinity with the residual fraction followed by the amorphous Fe/Mn fraction. Cu and Zn were more expressive in the amorphous Fe/Mn fraction followed by the organic one and crystalline Fe/Mn fraction, respectively. According to Igeo index, sediments proved to be highly polluted by Zn and Cu and moderated polluted by Pb. Despite the actual contamination of Jurujuba sediments, the mobility of these elements seems to be limited since the most excessive concentrations were found in the less available fractions, depending on extreme physico-chemical variations to be released.