Assessment of Heavy Metal Contamination of the Environment in the Mining Site of Ouixane (North East Morocco)

This study aims to assess the metallic contamination of soils and water resources in the environment of the Ouixane mining area (North East Morocco). Six metallic elements (Fe, Cu, Pb, Zn, Ni, and Cd) were analyzed by ICP-AES and ICP-MS. To evaluate the contamination of the soils, three contamination assessment methods were used as follows: enrichment factor (EF), pollution index (PI), and geo-accumulation index (Igₑₒ). The results showed that the soils of the studied area are highly enriched in metallic elements Cd, Cu, Zn, and Pb. Thus, the enrichment factor (EF) revealed an anthropogenic contamination of the majority of studied soils with an extreme contamination by Cd (EFₘ = 59.29), Cu (EFₘ = 45.93), and Zn (EFₘ = 44.73). The results of PI revealed extreme contamination by Cu (PIₘ = 7.12) and considerable contamination by Zn (PIₘ = 5.61), Cd (PIₘ = 4.83), Fe (PIₘ = 3.09), and Pb (PIₘ = 3). The Igₑₒ results showed strong contamination for most of the metallic elements and extreme accumulation for Cu and Zn in the Axara-Imnassen lake and the valley located downstream from the Ouixane deposit. Depressions and lakes are highly contaminated by heavy metals due to the leaching phenomenon of surrounding geological formations rich in sulfides. The significant leaching of metallic elements (Cu, Pb, Zn, Ni…) led to significant acid mine drainage (AMD). On the other hand, the geochemistry of the water samples revealed the transfer of metallic pollutants to the water resources which become very acidic locally. Using the contamination degree index (Cd), surface water was found to be highly contaminated by heavy metals (Cd > 3) compared to well water (1 < Cd < 3). Contamination assessment indices combined with the geographic information system (GIS) have been used successfully to identify the most polluted sites.