Grain Size Distribution and Enrichment Evaluation of Trace Metals in the Mediterranean Harbor Lagoon (Kalaât Andalous, Tunisa)

Abstract

Sediments are important carriers of pollutants and they help greatly in describing the aquatic ecosystem relating state. The aim of this study is to characterize the Kalaât Andalous harbor lagoon sediments’ grain size, their spatial distribution as well as their relating quality. To this end, a study of their trace elements content has been conducted to highlight the associated natural and anthropogenic contribution. Hence, twelve subsurface lagoon sediment samples were extracted at the level of six radials and subjected to a granulometric analysis. The calculation of such indexes as the average mean size (MZ), sorting index (r) and asymmetry index (SKI) helped greatly in defining the grain size-distribution character. Samples underwent different analyses in a bid to evaluate seven trace metals relevant rates (As, Cd, Cr, Cu, Ni, Pb, Zn). The obtained metal concentrations were compared to the American Oceanic and Atmospheric Administration (NOAA) guidelines, ERL and ERM. The enrichment factor (EF) analysis is used to assess the contamination level, and distinguish both of the relating natural and anthropogenic origin sources. The reached results proved to display that the sediments turn out to be predominantly sandy, with fine sand dominating the area, while medium sand is being located at the channel and the south-western section of the quay. The latter is characterized with a muddy facies. The majority of trace elements’ concentrations are discovered to be lower than the ERL values. The implemented enrichment factors proved to indicate that the lagoon is mainly enriched in As and Cd.