| Gaia: | Due to increasing anthropogenic activities, trace metals (TM) remain a major concern particularly in semi-arid countries with limited water resources. In this context, the present study aims to understand the geochemistry of trace metals in bottom sediments from the Sebou basin, representing 1/3 of the surface water resources of Morocco. Total concentrations of trace metals (As, Cd, Co, Cr, Cu, Ni, Pb, Zn) and some physicochemical parameters were measured in the fraction < 63 µm. The order of abundance of the elements was Zn > Cr > Cu > Ni > Pb > Co > As > Cd. The enrichment factor calculation showed that 70% of the samples were naturally concentrated in trace metals, especially As and Ni, as well as Cd and Pb, except at some stations. On the contrary, the most enriched elements were Cr, Zn, and Cu. Chromium presented an enrichment higher than 5 and toxicity risks at some stations, such as the downstream Fez city known for its important tannery activities. A multivariate analysis of the data evidenced the strong link between the identified natural elements (As, Co, Ni) with clays and Fe and Al oxides, whereas elements (Cd, Cu, Cr, Pb, Zn) mainly derived from anthropogenic activities (industrial and domestic waste, agricultural inputs) were linked to phosphorus and, to a lesser extent, particulate organic carbon.
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