Degradation of mine site alluvial soil – the case of artisanal and small-scale gold mining in Ghana

Artisanal and small-scale mining (ASM) is contributing to land degradation and loss of fertility of agricultural soils in Ghana. Although there is a legal requirement for soil restoration after mining, it is rarely carried out, and when it is done, it is often inconsistent with regulatory requirements. Community lands are therefore left impoverished since they no longer support crop farming. This study investigates the extent of soil degradation caused by alluvial mining in the West Akim Municipality of the Eastern Region, Ghana, by examining the physicochemical properties of three soil types: undisturbed/unmined, rehabilitated, and mined. Physico-chemical properties were analysed using depth-function plots and Index of Deterioration (I.D). Mined soils exhibited the highest levels of physical and chemical degradation., The surface horizon of mined lands exhibited greater deterioration, with I.D. values of 59%, 66.2%, and 77.5% for CEC, organic carbon, and Ca²⁺, respectively. The mean bulk density of rehabilitated soil is high (1.4), which is likely to diminish the soil's ability to support crop production. Similarly, mining decreases the bioavailability of nutrients. Pb, Cd, and Hg exceeded guideline limits across all soil horizons, with maximum values of 129 mg/kg, 43.45 mg/kg, and 2.50 mg/kg, respectively, recorded in mined soils. Multi-element contamination, enrichment factor, contamination factor and geoaccumulation indices indicate anthropogenic sources of the heavy metals in both mined and rehabilitated soils. It is concluded that both the mined and the rehabilitated lands are degraded, though to a lesser extent in the rehabilitated land. The lower ID of the rehabilitated land suggests that it is still beneficial to undertake rehabilitation, irrespective of how poorly it may be done.