Abstract

This study comprises soils formed on Paleoproterozoic Birimian Basement rocks (poorly graded silty sand, gravely sand and silty clays) from the unsaturated zone of the Densu River Basin, taken from a five meter depth. Elemental analysis of the soils samples were carried out by Energy Dispersive X-ray Fluorescence (EDXRF) to ascertain the levels of major and trace elements (K, Ca, Ti, Fe, Mn, Zn, Cu, Zr, Sr, Y, Pb, V, Cr, Ga, Ni and Rb) and to determine by statistical analysis the soil components which control the vertical distribution and the geochemical processes associated with the migration of the elements. The results indicated that there was general leaching of the base cations (K and Ca) near the surface 25 to 75cm depth while Fe and Ti concentrations remained fairly constant. Iron was the most abundant element found in the soil with concentrations ranging from 23.84g/kg to 143.70g/kg. The physicochemical analysis on soils shows moderately acidic to alkaline (pH_H2O range 5.6 to 8.3) and reducing properties, Eh (mV) ranged from -107.1 to +50.2. Enrichment factor calculations show the metals were depleted or of minimal enrichment (EF values between 0 to 12.14) due to human activities. Cluster analysis of the samples shows only one sample is needed from depths characterised by similar physical properties of texture and colour.

Key words: Unsaturated zone, energy dispersive x-ray fluorescence, vertical distribution, enrichment factor, cluster analysis.