Influence of anthropogenic activity on the vertical distribution of Zn, Cd, Pb and Cu in interstitial water and coastal marine sediments (Cadiz Bay, SW Spain)

Abstract

The vertical profiles of Zn, Cd, Pb and Cu were determined for sediment and interstitial water from three stations in Cadiz Bay. The concentrations of the different metals measured in the surface sediments depend on the distance from the waste water discharge points existing in this zone and on their nature (urban or industrial). The highest levels of Pb and Cd (70 and 0.31 μg g-1, respectively) were found near urban effluents, and the highest levels of Zn and Cu (230 and 106 μg g-1, respectively) near industries related to the construction of ships. The vertical profiles of Zn, Cd, Pb and Cu in both sediment and interstitial water show an important increase in concentrations in the surface layers and are relatively constant from 20 cm. The interstitial water concentrations are lower than the sediment concentrations, ranging from 13 to 57 μg L-1 for Zn, from 3 to 11 μg L-1 for Pb, from 9 to 320 μg L-1 for Cu and from 0.07 to 2.4 μg L-1 for Cd. The values obtained for the geoaccumulation index reported by Muller (1979) classify the study area as intermediate, between an uncontaminated and moderately contaminated ecosystem. The surface enrichment factor values calculated for the four metals from the different stations suggest a unique origin of metal contamination in this zone.