Geochemistry of sediments from El Melah lagoon (NE Tunisia): A contribution for the evaluation of anthropogenic inputs

摘要

El Melah is a small coastal lagoon of the Mediterranean Sea (NE Tunisia), with an artificial outlet and a closing evolution dynamic (sabkha). Marine environment samples (lagoon mouth and marine channel) are mostly tidal inputs, sands with low amounts of fine particles and low Al contents. High contents of trace elements found in these sediments can be due to their incorporation in carbonate phases. As far as the lagoon region is concerned, an attempt is made to evaluate anthropogenic inputs of trace elements contaminants, analysing surface sediments collected in 2001 and 2003. Distribution patterns of As, Co, Cr, Cu, Mn, Ni, Pb, Sb and Zn, as well as other trace and major elements, were studied. Trace elements contents normalized to Al and enrichment factors (EF) of trace elements, calculated relative to Al and using an internal reference sample, point to background natural variation of the potentially pollutant trace elements in the majority of the sites (EF < 3). Exceptions were found for Cu, Ni and Zn in the confined area of the Slimene purifying station, where deposits of urban solid wastes also exist without any protection for possible drainage and leaching. Despite the low enrichment factors found of trace elements, a general increase towards the most confined areas was observed.