Assessment of heavy metals contamination and their potential toxicity in the surface sediments of Sfax Solar Saltern, Tunisia

Concentrations of six heavy metals such as Fe, Pb, Zn, Cu, Ni and Cd have been examined in 20 surface sediment samples from Sfax solar saltern in order to evaluate their contamination levels; such concentrations (expressed in mg/kg of dry weight) have shown that Fe varied from 8750 to 8889.1, Pb from 18.98 to 233.46, Zn from 39.92 to 574.89, Cu from 13 to 98, Ni from 17.47 to 160.92, and Cd from 4.86 to 37.42. Importantly, the highest metal concentrations—except for Fe—have been more significant in sites frequently exposed to the industrial plumes of the local pollutant sources on the one hand and in sites often overwhelmed by high tide marine's water draining industrial waste from the port area on the other hand. Calculated enrichment factors have shown a spatial distribution in consistency with that related to concentrations. Complementary statistical approaches based on principal component analysis and hierarchical cluster analysis have proved that Fe is natural and other analyzed metals are anthropogenic. The geoaccumulation index has shown different contamination and toxicity levels, which have been confirmed by the study of mean-effect range medium-quotient, demonstrating a high probability of toxicity ranging from 49 to 76%, especially at sites with the highest metal concentrations. It has been suggested by the potential ecological risk index that the combined ecological risk of anthropogenic metal differ from one site to another, which highly significant in the case of Cd.