Origin of Metallic Pollution of Sediments from Multi-Purpose Dams in Northern Côte d'Ivoire: Cases of Korhogo, Tengrela, Boundiali, Katiola and Séguela Dams

Abstract

  Aims: To identify potential sources of metallic trace element (MTE) pollution in the sediments of five dams in northern Côte d'Ivoire by analyzing MTE concentrations and correlating them with anthropogenic activities in the watersheds. Study Design: Metallic trace elements content of sediments samples were analyzed. Then, the pollution origin has been determined through principal component analysis and field surveys. Place and Duration of Study: Dams in the cities of Korhogo, Boundiali, Séguéla, M'béngué, and Sinématiali, northern Côte d'Ivoire. Sampling was conducted during a defined period (between January and December 2022). Methodology: Sediment samples were taken from 15 stations across five dams (three stations per dam: entrance, middle, and dike), with both surface and depth (1 m) samples collected. Concentrations of ten metallic trace elements (Hg, Al, Cu, Cn, Cr, Ni, Fe, Mn, Pb, Zn) were determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). Source identification was performed using a two-pronged approach: principal component analysis (PCA) of the geochemical data and a field survey of anthropogenic activities in the surrounding watersheds. Results: Out of the ten MTEs analyzed, the majority had concentrations below standard thresholds. However, Aluminum (Al) was consistently high across all dams, reaching a maximum concentration of 24,333.33 mg/kg at Boundiali. Chromium (Cr) exceeded the standard limit of 31 mg/kg, with a mean concentration of 396.23 mg/kg at the entrance station of the Séguéla dam. Zinc (Zn) was also of concern in Séguéla (116.83 mg/kg) and Boundiali (99.27 mg/kg). The PCA analysis identified two main sources of pollution: a natural origin, linked to soil erosion and the earth's crust composition, and an anthropogenic origin, associated with urban reinforcement activities (e.g., in Korhogo) as well as domestic and agricultural discharges. Conclusion: The study confirms that while some MTEs are naturally occurring, anthropogenic activities are significant contributors to metallic pollution in dam sediments. Identifying these non-geogenic sources is crucial for developing targeted management strategies to mitigate water resource degradation and reduce associated health risks. Continuous monitoring and source control are recommended.