Geochemical Composition and Heavy Metals Enrichment of Pond Sediments of the Kanem Region (Republic of Chad)

Chemical analyses were carried out on sediment samples from ponds of the Kanem region to assess their composition and potential enrichment in heavy metals. The contents of major and trace elements are highly variable. Normalized profiles with Upper Continental Crust show various enrichments and decreases. The contents of major and trace elements often differ from those of recent deposits in the Lake Chad region. The sometimes-high contents of MgO, CaO, and Na2O are associated with the evaporite regime. The composition of the pond sediments, characterized by low Al2O3 content and highly variable SiO2 and other major elements, is distinct from clays and similar to that of sand and marl. The total REE content is lower than the PAAS. The REEs are associated with the fine fraction of sediment. Individual pollution indices reveal varying enrichments of As, Ba, Cd, and Mn, likely attributed to the use of fertilizers for food crops in the ouadis, and Mo, possibly of natural origin. The contents of enriched elements are below the threshold levels for agricultural land use, except for the Ba content of the ouadi of Manpal. The integrated pollution indices show variable global pollution levels. Regardless of the integrated index considered, the Manpal ouadi exhibits the highest level of sediment pollution