Ecological risk evaluation of sediment metals in a tropical Euthrophic Bay, Guanabara Bay, Southeast Atlantic

• We analyzed metals, total organic carbon contents and grain size of surficial sediments from Guanabara Bay.
• Sediment quality guidelines and acute and chronic toxicity bio-assays were done.
• Contamination status was determined based on geo-accumulation index and enrichment factor.
• ΣSEM/AVS indicated that metals were not available to the biota.
• Northwestern and the Harbour of Rio de Janeiro zones had the worse environmental conditions.

Surface sediments were collected from Guanabara Bay, at 14 stations distributed in five sectors, over three sampling campaigns. Analyses of metals, grain size fractions and total organic carbon analyses were performed. The geo-accumulation index and the enrichment factor were estimated to assess contamination status based on background values. Additionally, the sediment quality guidelines were applied to evaluate the adverse biological effects. Results show that there was no seasonal variation in sediment quality based on any methodology, and all methods utilized showed that NW sector and HRJ sector were the worst affected and that the NE sector had the best conditions. The sediments of GB are polluted mainly by Cr, Pb and Zn. According to ΣSEM/AVS, these metals are not available to the biota, although toxicity tests dispute this. Among the various methods employed, those using background values for the area seem to best reflect the local historical contamination.