Contamination levels and vertical distribution of trace metals with application of geochemical indices in the sediment cores of the Bizerte Lagoon-Ichkeul lake complex in northeastern Tunisia

The Bizerte Lagoon-Ichkeul Lake complex represents an ecosystem where the Tinja channel connected the Ichkeul Lake to the Bizerte lagoon. For a rigorous environmental assessment of pollution status, 17 core samples were collected in the complex area. The main purpose was to follow vertical distribution of trace metals and evaluate their potential contamination levels via an integrated geochemical approach. The collected samples were subjected to physicochemical characterization by several analytical techniques. Our results indicated that the mean concentrations of Cd, Cu, Pb, Mn, Zn, and Fe reached 2.31, 2.23, 33.22, 100.88, 40.79, and 605.05 mg/kg, respectively. They followed the order of Fe > Mn > Zn > Pb > Cd > Cu. The highest metal concentrations were found in samples close to industrial and urban areas transferred via the surrounding rivers. Those concentrations were lower than the effects range low (ERL), the effects range median (ERM), the threshold effect level (TEL), and the probable effect level (PEL), except for Cd and Pb. In addition, measured enrichment factor (EF), the geo-accumulation index (I-geo), and contamination factor (CF) proved the anthropogenic origin of all the potentially toxic metals studied. A low contamination for Cu, Mn, Zn, and Fe combined with very high contamination levels of Cd and Pb further confirmed the high anthropogenic input.