Spatial variability of trace metals in surface and groundwater within a contaminated mining environment in Ghana

Abstract

The aim of the study was to spatially assess the distribution of heavy metals within the catchment of the Tarkwa mining area using interpolation techniques in a geographical information systems environment. Water quality trends for 84 sites in Tarkwa, a mining district in Ghana, were examined for fourteen (14)parameters-pH, conductivity, Total Dissolved Solids (TDS), turbidity, nitrates, sulphates, Chemical Oxygen Demand (COD), total cyanides, arsenic (As), cadmium (Cd), iron (Fe), manganese (Mn), nickel (Ni) and lead (Pb). Kriging was utilized to illustrate the spatial patterns of variables. The results showed that surface and Ground water are contaminated by As, Cd, Fe, Mn and Pb with the average concentrations exceeding World Health Organisation guideline values. The spatial dependence of the heavy metals was assessed using variogram parameters which varied from 320.30 to 4842.25 m. Significant correlations were found among heavy metals, which suggest a common origin. This is confirmed by the cluster analysis which indicated that Fe, As and Pb belonged to one group. The use of geostatistical tools in water quality assessment in this study enhances our understanding of spatial trends