Heavy Metal Loading in Surface Sediments Along the Kawere Stream, Tarkwa, Ghana

Abstract

Sediment contamination with heavy metals due to increasing anthropogenic inputs poses risk to human well-being and ecological integrity at large. The purpose of this study was to assess the heavy metal loading in sediment along the Kawere stream. Ten sediment samples were analysed for Cu, Pb, Cd, Mn, Zn, Ni, Cr, Co and Fe using a Varian AA240FS Atomic Absorption Spectrometer (AAS). The Australian and New Zealand Environment and Conservation Council (ANZECC) guidelines for freshwater sediment quality was used as the benchmark against which the measured metal concentrations were compared. Nemerow’s pollution and potential ecological risk indices were computed to evaluate the pollution status and ecological risk levels of the heavy metals in the stream. Results indicated that all metals concentrations were below their corresponding ANZECC values. However, at sampling sites K01, K05 and K07 measured Cu concentrations of 171.29, 170.83 and 113.31 mg/kg respectively exceeded the ANZECC trigger value of 65 mg/kg. Heavy metal pollution assessment showed that 3 sampling sites (K01, K05 and K07) were slightly polluted, suggesting that these sites are likely to pose health threat to the aquatic organisms and humans. Calculated ecological Risk Index (RI) ranged from 3.229 to 19.750 (RI < 150), representing a low ecological risk. As such, the metals, Cu, Ni, Cd Pb, Cr, and Zn pose low ecological risk to the aquatic ecosystem.