Determination of Some Selected Heavy Metals in Fish and Water Samples from a Section of Migori River

Abstract

Samples of Tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus) were collected from a section of Migori River. The moisture content of freeze-dried body of the fish collected from four sites ranged between 62.6% and 86.6% (m/m). An optimal procedure required 12 mL mixture of HNO₃, HClO₄, and H₂O₂ (3:2:1, respectively) to mineralize powdered samples in open refluxed digestion vessels: 0.5 g of the fish body. The concentrations of 3 toxic elements Cd, Pb and Hg) in the body of the fish was determined by atomic absorption spectrophotometer. The concentrations varied, respectively; Cd = 0.4 - 1.85, Pb = 0.05 - 0.5 and Hg = 0.07 - 0.096 in mg of element/kg of fish. The concentration of those three heavy metals in water samples was also determined similarly and varied, respectively, as (mg of element/L of water sample); Cd = 0.06 - 0.66, Pb = 0.28 - 0.36 and Hg = 0.5 - 0.74. Application of the statistical t-test on heavy metal elements data has shown that there was a significant difference between the mean concentrations of Hg in water samples. There is no significant difference between fish as well as water sample from the river.

Keywords: Tilapia Fish, African Cat Fish, Clarias Gariepinus, Oreochromis Niloticus, Toxic Metals, Water Pollution, Migori river.