Multivariate analysis of potentially toxic elements in surface waters in Ethiopia

The Akaki River and its tributaries, in the city of Addis Ababa, are polluted by potentially toxic elements (PTEs) (Sb, Zn, Cd, As, Hg, Cu, Pb, Fe, V, Ni, Co, Mn, Cr, B, Sr and Ba) in varying degrees due to the significantly fast urban expansion and the industrial activities. The water samples collected from twenty-six different locations or sampling sites along the River and some of its tributaries were analyzed by ICP-MS to determine PTEs. The multivariate component analysis was used to evaluate the relationship and interdependency among the PTEs. The results showed that the mean concentrations for most of PTEs exceeded the recommended limits of drinking and irrigation water quality guidelines. A strong and positive relationship was observed among many of PTEs in the river water indicating common sources. The concentrations of many PTEs in the study area exceeded those previously reported and also varied with site or location, signifying localized contributions of the different contaminants associated with municipal, domestic, industrial, hospitals, garages and other activities. These findings of this study should help highlight and focus water quality management on key PTEs of concern and prioritize efforts to mitigate their release into surface waters in the city. Given the potential health implications of the PTEs mitigation measures should be sought as a matter of urgency by the relevant authorities in Ethiopia.