Contamination of superficial sediments by heavy metals and iron in the Bizerte lagoon,northern Tunisia

According to the norms adopted by the National Network of observation of the marine life quality (RNO 1997) and US National Oceanic and Atmospheric Administration (US NOAA 1999), the superficial sediments of the Bizerte lagoon (northern Tunisia) show a contamination by nickel, which is the probable consequence of the closeness to the industrial zone, and by lead, the result of detrital material rich in lead of the geological lands of Jbel Kchabta and Jbel Messeftine. In the lagoon southern and eastern sectors, the contamination of superficial sediments is essentially by copper, zinc, nickel and iron. This pollution is related, on one hand, to the rejections of the steelworks El Fouledh and the military arsenal, and on the other hand, to Menzel Bourguiba waste disposal. The rest of the lagoon is exempted from any metallic contamination of the surface sediments. The enriched zones in manganese and zinc correspond to the higher contents in kaolinite and in smectite. Positive correlations were recorded between the percentage in fine fraction on the one hand, and the sedimentary contents in TOC, total nitrogen and heavy metals on the other hand. The majority of the analysed elements are “argilophilous” except zinc and manganese, which are clayey organophile. These results show that this lagoon receives concentrations in anthropogenic metals that risk provoking more or less important disruptions, which are harmful and irreversible on the fauna and flora of this lagoon and on the whole ecobiological equilibrium.