Determination of post-dredging concentrations of selected trace metals in water, sediment and the freshwater mudfish (Clarias gariepinus) from Ikpoba river in Benin City, Edo State, Nigeria

Abstract

This investigation monitored the post-dredging concentrations of Cu, Mn, Zn, Cr, Ni and Pb in the water, sediment and the freshwater mudfish, Clarias gariepinus, from Ikpoba River in Benin City, Nigeria, over a six-month (February – July, 2005) period. The results showed that the levels of Mn, Ni and Pb in water and Cu, Mn, Cr and Pb in fish were higher than the recommended levels in drinking water and food fish and could pose health hazards. The results also showed that the post-dredging metal contamination levels in water and sediment of the river were lower than available pre-dredging levels, but in fish the differences between the post-dredging and pre-dredging levels were not significant and suggested that dredging could reduce metal contamination levels in the river. Consequently, continued dredging of the river is recommended as it has the potential to substantially improve the quality of the water and reduce hazards posed by heavy metals to the livestock and human population that depend on the river for drinking and other uses. Key words: Trace metals, pollution, Ikpoba River, Nigeria.