Physicochemical Characteristics and Heavy Metals Contamination Assessment in Water and Sediment in a Tropical Hydroelectric Dam of Sassandra River, Côte d’Ivoire

Abstract

Buyo hydroelectric dam is one of the highest concrete rock-filled dams in Côte d’Ivoire. This paper presents results of physicochemical parameters in water supply, heavy metals concentrations, and ecological risks in sediment from Buyo hydroelectric dam. In-situ measurement of physicochemical parameters of water and sediment samples were collected in 3 stations along the reservoir from April 2018 to March 2019. The sediment samples have been acidic digested and metal concentrations were analyzed using an atomic absorption spectrophotometer and mercury analyzer. Results indicated that conductivity, oxygen content, temperature, nitrite, and chloride were within the limits established by WHO for potable water, while pH was acidic. The Pearson correlation indicated a strong positive correlation and significant linear relation between various pairs physicochemical parameters. In comparison with upper continental crust concentrations, all heavy metals in sediments showed high concentrations in the upstream than the downstream and pristine stations, with exception of Cu. The geo-accumulation (Igeo) and enrichment factor (EF) indices used indicate that sediments were classified as uncontaminated according to Zn and Mn concentrations and they have a lithogenic source. Whereas, Igeo and EF values of Hg and Cu showed that the sediments lie in the range of moderate to heavily contaminated, suggesting anthropogenic inputs on these metal levels. Except for Hg, which had high ecological risks, Cu, Zn, and Mn pose a low ecological risk. This study provides an insight into water qualities and risk assessment of environmental pollution and important outputs for decision-makers to set policy for resources management.