Luanda bay has been acting as a sink for the untreated municipal and industrial effluents from a part of the city. Sediment samples were analyzed for their total organic carbon contents and pseudo-total concentrations...Luanda bay has been acting as a sink for the untreated municipal and industrial effluents from a part of the city. Sediment samples were analyzed for their total organic carbon contents and pseudo-total concentrations ofFe, Mn, Hg, Cd, Pb, Cu, Zn, Ni and Cr The highest concentrations of organic carbon and Hg, Cd, Pb, Cu and Zn were found near the sewerage discharge outlets, exceeding in these points the lowest Sediment Quality Guidelines for the occurrence of adverse biological effects. A further study, based on the latest version of the BCR sequential extraction procedure, was undertaken in order to assess the physical/chemical binding and bioavailability ofFe, Mn, Cd, Pb, Cu and Zn in these sediments. The toxic metals Cd, Zn, Pb and Cu pose a potential environmental risk, because they were extracted from the sediment labile fractions in concentrations that exceeded the corresponding ERL （Effects Range Low） values, entering the range within which adverse biological effects occur. The non-residual fractions of metals ranged from 91 to 100% for Cd, 89 to 94% for Zn, 67 to 100% for Pb, 71 to 82% for Cu, 30 to 77% for Mn and 39 to 48% for Fe. Measures to be taken for the disposal of the polluted dredged sediments are shown in this work.展开更多
文摘Luanda bay has been acting as a sink for the untreated municipal and industrial effluents from a part of the city. Sediment samples were analyzed for their total organic carbon contents and pseudo-total concentrations ofFe, Mn, Hg, Cd, Pb, Cu, Zn, Ni and Cr The highest concentrations of organic carbon and Hg, Cd, Pb, Cu and Zn were found near the sewerage discharge outlets, exceeding in these points the lowest Sediment Quality Guidelines for the occurrence of adverse biological effects. A further study, based on the latest version of the BCR sequential extraction procedure, was undertaken in order to assess the physical/chemical binding and bioavailability ofFe, Mn, Cd, Pb, Cu and Zn in these sediments. The toxic metals Cd, Zn, Pb and Cu pose a potential environmental risk, because they were extracted from the sediment labile fractions in concentrations that exceeded the corresponding ERL （Effects Range Low） values, entering the range within which adverse biological effects occur. The non-residual fractions of metals ranged from 91 to 100% for Cd, 89 to 94% for Zn, 67 to 100% for Pb, 71 to 82% for Cu, 30 to 77% for Mn and 39 to 48% for Fe. Measures to be taken for the disposal of the polluted dredged sediments are shown in this work.
