The concentration levels of selected iron-ore composite heavy metals were investigated in mainstream sediment of River Osara traversing by Itakpe iron-ore deposit and mining area in North Central Nigeria. The sediment samples collected along the drainage course, up-, mid- and downstream for 24 months were digested using standard methods, and levels of Cd, Cr, Ni, Cu and Pb determined using flame atomic absorption spectrophotometer (AAS). The mean concentrations of Pb, 15.63±2.35-18.98±2.04 mg/kg was the highest followed by Ni, 5.20±1.79-15.83±3.04 mg/kg, relative to other metals. The concentrations of Cu and Cr were 3.18±1.14-10.02±2.89 mg/kg and 1.12±0.27-20.93±4.89 mg/kg,respectively, while Cd, 0.24±0.12-0.40±0.26 mg/kg was the least. There was significant (p < 0.05) positive correlation between the concentration of the measured metals with organic carbon level in sediment, with coefficient of correlation γ=0.68, Cd; γ=0.69, Ni; γ=0.54, Cr; γ=0.85, Pb and γ=0.81, Cu implying that metals levels in sediments are partly defined by organic carbon levels. Seasonal fluctuations were observed in sediment concentrations of metals with higher concentration during dry season than in wet season.The concentration of heavy metals in River Osara sediment by Itakpe iron-ore deposit and mining area are low and within natural concentration levels. The result could serve as benchmark required for effective water management and environmental monitoring.
Key words: Heavy metals, concentration, bottom sediment, iron-ore, monitoring, River Osara, Nigeria.
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