Trace Metal Contamination and Associated Ecological and Human Health Risk Assessment in Before Sediments of the Koko Watershed (Korhogo, Côte D’Ivoire)

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Résumé

The contamination of aquatic environments can be caused by several types of pollutants, notably heavy metals. Heavy metals present in ecosystems have become a significant environmental risk. Thus, sediments, which are the major sinks of these contaminants, may represent a significant environmental concern to human well-being, aquatic plants, and various benthic organisms. The objective of this study was to assess sediment quality in order to examine the potential ecological and health risks associated with heavy metal concentrations in sediments. Sediment samples from streams and the river of the Koko watershed were collected and analyzed for the presence of Pb, As, Zn, Cu, Ni and Cr using atomic absorption spectrophotometry (AAS). The heavy metal concentrations obtained from the analysis revealed that the highest average concentrations for Pb, Zn, Cu, Ni, and Cr were recorded during the dry season, with 35.60, 101.26, 23.36, 26.80, and 80.12 mg kg-1, respectively, whereas As reached its highest average concentration during the rainy season (1.51 mg kg-1). The results generally indicate that the accumulation of trace metals varies according to both the sampling site and the season. Comparison of our data with Upper Continental Crust (UCC) values indicates that the studied sediments are contaminated with Pb, As, Zn, Cu, Ni, and Cr in the dry season. This result is supported by the geo-accumulation index (Igeo), which generally indicates moderate contamination of sediments 1, 2, 3, and 5 by Pb, As, Zn, Cu, Ni, and Cr. The quality of the sediments indicates a potential toxic risk to benthic organisms at sediment 3 (PERI: 393.72) during the rainy season and in the dry season (PERI: 342.34). In the rainy season, the m-ERM-Q indicates a moderate-to-low probability of ecosystem hazard, although Ni poses a high-risk level in all sediments. But in the dry season, Ni has a moderate-to-high ecological impact on biota in all sediments.

Mots-clés

Heavy Metals, Sediment Quality Indices, Potential Ecological Risk, Potential Human Health Risk