An assessment of total petroleum hydrocarbon and trace metal concentration in the sediments of Ugbo water way, South western Nigeria

Abstract

Sediment samples from Ugbo water way, South Western Nigeria were assessed for total petroleum hydrocarbon (TPH) and trace metal concentrations. Seven sampling stations were selected and one control station. Total petroleum hydrocarbon (TPH) in the sediment samples was determined using Gas Chromatography-Flame Ionisation Detector (GC-FID) while trace metal concentrations were determined with Atomic Absorption Spectrophotometer (AAS). In situ measurement of the physicochemical parameters of the water was done during sampling. The average concentration of TPH in the sediment samples is 0.131 mg/kg which is far well below the maximum permissible limit (10 mg/kg) and the occurrence of the measured trace metals is in the decreasing order for the different metals Fe>Pb>Zn>Cu>Ni>Mn>Cd. Fe had the highest concentration with an average value of 0.845 mg/kg while Cd had the lowest average concentration of 0.032 mg/kg. The highest concentration of the TPH occurs at the point of offload of petroleum motor spirit (K5) and increases outwards in the down current direction as we travel away from K5. The levels of Cd, Fe, and Mn all exceeded the U.S.E.P.A recommended limit, while the rest of the metals (Pb, Zn, Cu, and Ni) were found to be within recommended limits.