HEAVY METAL CONTAMINATION AND PHYSICO-CHEMICAL ASSESSMENT OF THE DENSU RIVER BASIN IN GHANA

Abstract

Physico-chemical and Trace metal analyses were carried out on water and sediment samples from the Densu river in Ghana to ascertain the water quality. The pH values ranged from 6.55 to 7.33 and were within the natural background level of 6.5 – 8.5. The Total Dissolved Solids (TDS) values ranged from 67.1 to 113.0 mg L-1 and were below the World Health Organization (WHO) recommended value of 1000 mg L-1. The Electrical Conductivity (EC) values ranged from 150.3 to 223.0 µS cm-1 and were below the acceptable value of 350 µS cm-1 for unpolluted river. The salinity values were generally insignificant. The Atomic Absorption Spectrometry (AAS) technique was used for the trace metal analysis. The elemental analysis was done for Cd, Cu, Fe, Hg, Mn, Ni and Zn. The analysis gave Fe (1.590 – 6.090) mg L-1, Mn (0.039 – 0.661) mg L-1 and Zn (0.005 – 0.021) mg L-1 in the water samples. The concentrations of Cd, Cu, Hg and Ni were below their respective detection limits for the analytical method used. The elemental concentrations in the soil sediments were Cu (6.0 – 46.5) mg kg-1, Fe (11,200 – 47,800) mg kg-1, Mn (143 – 1488) mg kg-1 and Zn (6.5 – 108.0) mg kg-1. Cd, Hg and Ni levels were below their respective detection limits. Enrichment factor computation for the soil sediments revealed that there could be moderate anthropogenic contributions to the levels of Mn and Zn in the sediments.