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Abstract
Microwave-assisted acid digestion and modified aqua regia (HNO3:HCl:HF:H3BO3) leaching techniques were used for the determination of 15 potentially toxic elements (V, Cr, Fe, Mn, Co, Ni, Cu, Zn, As, Se, Ag, Cd, Sn, Hg and Pb) in sediment samples from Lake Awassa and Lake Ziway, Ethiopia. The digests were subsequently analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-optical emission spectrometry (ICP-OES). Mercury was directly determined in the solid samples using an elemental mercury analyzer. The precision and accuracy of the digestion procedures were verified using certified reference materials. The experimental results were in good agreement with the certified values (P < 0.05) and the recoveries were quantitative (>90%). The average relative standard deviations were below 10%. There is significant correlation between the two lakes at the 0.01 level (2-tailed). Using the sediment quality guidelines, both lakes are heavily polluted with Zn and some of the sites are heavily polluted with Cu, Ni and Pb. Based on effect range low (ERL) – effect range medium (ERM), in both lakes for Ag were greater than the ERM, indicating that the areas could be toxic to aquatic organisms, while for Cr, Cu, As and Hg the values were less than ERL.
Acknowledgments
The authors acknowledge the Department of Chemistry of Addis Ababa University, Addis Ababa, Ethiopia and Department of Chemistry of Tshwane University of Technology, Pretoria, South Africa for allowing us to use laboratory facilities.
Funding
Financial support from Addis Ababa University, Addis Ababa, Ethiopia and Mekelle University, Mekelle, Ethiopia is duly acknowledged.
Supplemental material
Supplemental data for this article can be accessed on the publisher's website.