Heavy metal contributions of run-off waters discharging into the Ikpoba Reservoir during rainy season

Abstract

Heavy metals contributions of run-off waters from six sources discharging into the Ikpoba reservoir and the immediate upstream and downstreamIkpobaRiverwere investigated during the rainy season months (March – October) of 1991 and 1992. In the reservoir, the results revealed that the highest contribution of heavy metals came from Okhoro road (11.028%), followed by the solid waste dumpsite (9.256%) on the bank of the reservoir.  In the downstream Ikpoba section,Upper Mission Roadhad the highest percentage contribution of 11.67% while in the upstream section the Agricultural farm had the highest percentage contribution of 6.150%. Of all the metals, Zn had the highest percentage contribution (73.74%) while Cd had the lowest contribution (0.39%). Cd had the highest contribution in discharges fromUpper Mission Road, Cr and Zn fromOkhoro Road, Cu from the headworks discharge pipe, Pb fromUpper Lawani Road, Mn from the Agric. farm and Ni from the solid waste site.  The mean metal contributions of Cd, Cu, Pb, Ni and Zn from the six sources into the reservoir were higher than the mean contributions from upstreamIkpobaRiver.  Cr, Mn and Ni were also higher in the reservoir waters than the downstreamIkpobaRiver.