Sediment-associated trace and major metals in the headwaters of a tropical reservoir

Abstract

ABSTRACTBed sediment samples of the two headwaters of a tropical reservoir in Southwestern Nigeria were analysed for some metal concentrations using ICP-OES for a period of one year. Sediment samples were collected bi-monthly from both the lower and upper reaches of the streams from May 2013 to March 2014. Sediment samples were microwave-digested and analysed using ICP-OES. Concentrations of metals were higher in the lower reach than in the upper reach, and wet season concentrations were higher than in the dry season with the exception of Fe and Mn. The annual mean metal concentrations were as follows: Fe (121.72 ± 6.82 µg/g); Mn (9.34 ± 2.57 µg/g); Na (6.20 ± 2.29 µg/g); K (0.65 ± 0.57 µg/g); Mg (8.07 ± 1.36 µg/g); Ca (13.92 ± 2.85 µg/g); Ba (0.17 ± 0.17 µg/g); Al (106.54 ± 5.55 µg/g); and Se (0.6 ± 0.19 µg/g). These values were lower in comparison with the baseline concentrations of elements on the earth’s crust. Contamination assessment of all the metals investigated in this study showed that metals in the bed sediments of the two headstreams had not reached pollution status with the exception of Se.