Spatial distribution of heavy metals in drainage sediments of Axim-Tarkoradi area: Environmental implications of influence of surface geology and mineral occurrences

High concentration levels of heavy metals in drainage systems are major environmental concern in Ghana. The sources of these metals be it natural or anthropogenic are sometimes difficult to determine as no baseline studies were ever carried out to determine their reference levels under natural conditions prior to major human activities. The objective of this paper is to provide contribution on the spatial distribution of heavy metals and the environmental implications of the influence of surface geology and mineral occurrences in the Axim-Tarkoradi area, southwest Ghana. A total of 381 drainage sediments were collected and analyzed by ICP-AES for 19 elements (Cu, Li, Mn, Ni, Ca, Sr, Zn, Cd, Pb, As, Cd, Co, Ag, Cr, Fe, Mo, Ba, Sb and V) after partial acid extraction. Two groups of elemental associations were observed in the area. These are V, Co, Cr, Ni, Fe, Zn, Cu, As and; Mn and; Mo, Sr, Ba, and Li associations. The spatial distribution of the former is consistent with toleiitic basalts and the later with tonalitic granites. An analysis of variance test revealed that there is a relationship between the surface geology and the geochemical distribution patterns of the two elemental groups.