Levels of zinc, copper, iron and manganese in soils of abandoned mine pits around the Tarkwa gold mining area of Ghana

Abstract

Abandoned mine pits have been a health threat to the inhabitants of many mining communities in Ghana. In this paper, the concentrations of copper (Cu), zinc (Zn), iron (Fe) and manganese (Mn) in sand and clay soil samples from seven of such abandoned open mine pits in the Tarkwa gold mining district of Ghana, were examined. The mean Cu concentrations in the sand soil samples ranged from 6.5±0.50 µg/g to 56.17±1.61 µg/g. Abandoned mine pits 5, 6 and 7 recorded mean Cu concentrations slightly higher than the background concentrations. However the mean Cu concentrations in the clay soil samples were all less than the background levels. The mean Zn concentrations in the sand soil samples were between 4.17±1.23 µg/g and 43.17±4.75 µg/g. Similar pattern of this metal was registered in the clay soil samples. The mean Fe levels in the sand soil samples ranged between 8133±292 µg/g and 119166±135 µg/g. sampling site 5, 6 and 7 recorded mean Fe concentrations higher than the background levels. These elevated Fe concentrations in the sand soil samples may be due to the mining activities which took place in these pits. The mean Mn concentrations in the sand soil samples ranged between 26.67±1.44 µg/g and 1595±157.16 µg/g. These high levels may also be attributed to the mining activities in the area. The results of the quantification of the metal contamination of the soil samples using contamination factors and pollution load index (PLI) indicated that some of the studied pits are significantly polluted with Cu, Fe and Mn