Longitudinal profiles of total hydrocarbon, oil and grease and trace metal concentrations in surface waters of Qua Iboe River (South Eastern Nigeria) in relation to urbanisatio

Abstract

The total hydrocarbon content (THC), oil and grease and trace metal concentrations in surface waters of Qua Iboe River in South-eastern Nigeria were studied for three years in relation to increasing oil activity and urbanization in the drainage basin. Levels of THC varied significantly (P < 0.01) between the stations and were higher at stations close to urban areas and busy highways. THC exhibited pronounced intra-seasonal variability and concentrations increased with initial precipitation. Highest THC levels were recorded at estuary due to increasing oil activity and THC in estuarine water was significantly higher (P < 0.01) at disturbed (5.28 + 2.65 mg.l^-1) than at undisturbed sites (0.19 + 0.03 mg.l^-1). THC associated with particulate matter dominated the total hydrocarbon pool more than that associated with the filtrate with significant difference (P < 0.05) between them. Levels of oil and grease in surface waters were higher at estuary (6.54 + 0.62 mg. ^-1) and at stations close to urban areas than non-urban areas and varied significantly (P < 0.05) between the stations. Trace metal concentrations were higher at stations close to urban areas with highest concentrations at the estuary than non-urban areas. The dominant trace metals were Fe, Zn and Ca and concentrations were influenced by hydrological variables. Concentrations of total hydrocarbon, oil and grease and trace metals varied per station and were influenced by urbanisation and precipitation.


Key words: Longitudinal variation, total hydrocarbon, trace metals, urbanization.


Journal of Aquatic Sciences Vol.19(1) 2004: 41-47