Spatial and temporal variation of traces elements in surface water in the Agneby watershed (Côte d’Ivoire, West Africa).

Résumé

Water is vital for human beings. Preserve its quality and quantity is essential to ensure welfare to populations. The aim of this work is to determine the quality of surface water catchment of Agneby in Agboville. Investigations consisted in evaluating physicochemical parameters and trace metals of surface water in the basin. Indeed, the surface water samples were collected in five stations and during four different seasons. Physicochemical parameters (Temperature, potential Hydrogen, Electric Conductivity and Total Dissolved Solids) were measured in situ using a multiparameter Hanna (HI 991001 pH meter and HI 99300 conductmeter) while lead, zinc and copper were analyzed by molecular absorption spectrophotometer HACH DR 2800. The Principal Component Analysis and Hierarchical Ascending Classification showed the existence of two groups of water. The first included waters of the long dry season, highly mineralized with high contents of zinc (3.14 mg/L in Agboville and 6.49 mg/L to Afféry), copper (0.45 mg/L to Afféry and 3.3 mg/L to Kotchimpo). The second, characterized by high levels of lead (0.094 mg/L in Agboville and 0.19 mg/L in Copa), gathers waters of the long rainy and short seasons. Results of surface waters analysis revealed good mineralization (117 μS/cm in Afféry and 389 μS/cm in Kotchimpo during dried season) and the acidity of Kotchimpo waters (6.39 < pH < 6.43). Also, surface waters collected, whatever the station, were polluted by trace metal such as plomb (Pb > 0.01 mg/L). Mean concentrations of Cu registered were highly pollutant in Kotchimpo (1.25 mg/L), Agbossou (1.08 mg/L) and Copa (1.03 mg/L).