Potentially Toxic Trace Element Contamination of the Little Akaki River of Addis Ababa, Ethiopia

Abstract

In this study, river water samples taken from 26 different locations along the course of the Little Akaka River in Addis Ababa were analyzed to determine potentially toxic trace element concentrations. The mean concentrations in ?g L^-1 for Mn 1540.04, Fe 1075.92, B 383.04, Sr 336.75, Ba 132.17, Cr 67.04, Sb 42.80, Zn 25.50, Ni 6.66, Cu 5.61, V 4.87, Pb 3.13, Co 2.62, As 1.46, Cd 0.06 and Hg <0.05. Overall metal concentration were in the order Mn > Fe > B > Sr > Ba > Cr > Sb > Zn > Ni > Cu > V > Pb > Co > As > Cd > Hg. A strong positive correlation was observed between several of the trace elements indicating common sources. The concentrations of Cr, Mn, Sb, B and Pb exceeded the permissible limits of the Ethiopian, European Community and WHO for drinking water quality guidelines. Fe and Sr exceeded the permissible limits of the Ethiopian drinking water guideline and Sr exceeded the WHO thresholds. The concentration of Cr, Zn, Cu and Pb exceeded the annual average thresholds for surface waters set in SI 272 of 2009. The concentration of Cr, Mn and Sr were also higher than the international guidelines value for irrigation water. The pollution of the river water is increasing alarmingly and poses serious threat to human health. Many of the concentrations were higher than previously reported. It is, thus, necessary to take serious and essential measures from the concerned bodies. Adoption of adequate measures to remove the heavy metal load from the industrial waste water and upgrading of sewage treatment plants are suggested to avoid further deterioration of the river water quality.

Keywords: River water, Potential toxic elements, Heavy metal contamination, Drinking water standards