Evaluation of pollution and metal toxicity in the sediment of lake Dayet Er-Roumi, Morocco using environmental index and multivariate statistical approaches

The Lake Dayet Er-Roumi, classified as a Site of Biological and Ecological Interest (SBEI), is affected by several forms of anthropogenic pollution. This reason makes it necessary to study the condition of the natural lake to understand its functioning and its sensitivity to different pressures and degradation. The objective of this study is to assess the level of metallic contamination and quantify the degree of pollution through spatio-temporal monitoring of metal quality (Al, Pb, Mn, Ba, Zn, Fe, Co, Cu, Cd, Cr and Ni) at 3 stations during 4 seasons (2018/2019). The results revealed a high concentration of Zn, Pb, Cu, Cr, and Mn at all stations, especially during winter and autumn. These concentrations far exceed the recommended standards. The different contamination indices calculated show a very important enrichment; indeed, the contamination factor shows a very strong contamination for the Zn, Pb, and Cu, with a moderate contamination for the Mn and Cr. The results of the degree of contamination reveal a polymetallic contamination dominated by three elements, which are Zn, Pb, and Cu. Analysis of these indices allowed us to establish the classification order of the different stations in terms of contamination, which is as follows: S1>S3>S2. The calculation of the contamination indices confirms real polymetallic contamination, with worrying situations for several stations and several metallic elements. The hierarchical cluster analysis reveals common sources of these studied metals. The results obtained reflect extremely severe contamination by these elements and show strong pollution caused by local populations.