Distribution of heavy metals in marine sediments of Tetouan coast (North of Morocco): natural and anthropogenic sources

Abstract

The heavy metal concentrations (Al, Fe, Ti, Mn, Zn, Cd, Co, Cr, Ni, Pb and Cu) in sediment samples collected from the Moroccan Mediterranean coast were studied. The heavy metal concentrations obtained were similar or relatively low when compared with other Mediterranean zones. To assess their distribution and distinguish between their natural and anthropogenic sources, the enrichment factor (EF) index was applied. Consequently, minor enrichment by Cd, Cu, Fe, Mn and Pb was observed. The effects on aquatic organisms were established using sediment quality guidelines (SQGs). As a result, Cu concentrations were above the interim sediment quality guidelines (ISQG), Ni and Pb presented concentrations above the effects range low (ERL) while Cr was above the probable effect level (PEL) in some sampling points. In addition, a principal component analysis was performed showing that the distribution of metals in the study area seems to be influenced by both natural and anthropogenic sources. Nevertheless, the analysis of mineralogical composition has allowed the identification of a natural source as the most probable origin of some elements, such as Ni and Mn, related mainly to the geological background. In contrast, Fe, Cr, Co and Pb could be related to both natural and anthropogenic activities in the area while Cd and Cu seem to have an anthropic origin.