The preliminary assessment of the pollution status of streams and artificial lakes created by mining in the mining district of Enyigba, south eastern Nigeria, and their consequences

Abstract

The distribution of Pb, Zn, Cu, Cd, Ni and As in waters and sediments in streams and entrapped water bodies around the mining district of Enyigba was evaluated. The result of analyses show that the concentration of Cu varies from 0.006 to 0.100 mg/l in waters in streams and mine pits (surface water), with a mean of 0.02 mg/l; Zn from 0.008 to 0.023 mg/l with a mean of 0.01 mg/l. The concentration of Pb, Ni, Cd and As in all samples of surface water is lower than 0.001 mg/l. The concentration of Pb in sediments vary from 54 mg/kg to 63356 mg/kg with a mean of 4245 mg/kg; Zn from 72mg/kg to 1386.5 mg/kg with a mean of 349.68 mg/kg; Cu from 11.5 mg/kg to 808.5 mg/kg with a mean of 84.48 mg/kg; Cd from 0.5 mg/kg to 5.5 mg/kg with a mean of 3.35 mg/kg; Ni from 0.5 mg/kg to 1197 mg/kg with a mean of 282.66 mg/kg and As from 0.05 mg/kg to 1.5 mg/kg. It is established that there is no significant pollution of surface water by heavy metals analysed, based on WHO Standard of 1993. There is however significant pollution of sediments by Pb, Zn and Ni and to a smaller extent Cu. The consequences of the observed pollution include the introduction of pollutants in the downstream reaches of the streams and the Ebonyi River during the periods of high flow, the accumulation of the pollutants in the tissues of organisms that live in the sediments which may get passed to higher organisms that prey on these organisms and the eventual effect on humans, through the food chain.