Evaluation of Quality of Some Rehabilitated Mined Soils within the AngloGold-Ashanti Concession in Ghana

摘要

Land degradation caused by surface mining of gold has been extensive in Ghana. In recent years rehabilitation of some degraded lands by re-vegetation has been undertaken. This study provides quantitative data on the quality of some rehabilitated and un-rehabilitated mined soils within the AngloGold-Ashanti gold concession in parts of the semi-deciduous forest zone of Ghana. Soil properties determined included texture, bulk density and aggregate stability, pH, organic carbon, available phosphorus, total nitrogen, cation exchange capacity, exchangeable bases, exchange acidity, Fe, Mn, Ni, Cu, Zn, Cd, and Pb. Aggregate stability as a physical quality indicator revealed that aggregates of the rehabilitated mined soil had become more stable and similar to the control unmined soil due to litter and carbon additions from planted trees. The nutrient levels were very low because of the presence of low activity clays inherent in the native soil. Organic carbon content in the rehabilitated soil had increased above that of the unrehabilitated soil. Variability in soil properties, especially organic carbon and aggregate stability, was minimal in the unmined and rehabilitated soils implying that soils at the two sites were most robust and resistant to crushing and rupture. Quality index of the unmined control soil was 36.5% indicating that the quality of the soil was 63.5% relative to the optimum quality because of inherent poor soil properties. The mined rehabilitated and unrehabilitated soil had index values of 32.5% and 24.4 %, respectively. The marginal difference of 4% in soil quality between the control and rehabilitated soil shows that it is possible to maintain the health of soils with inherent physical and biochemical deficiencies if reclamation regulations are adhered to. In this way, the socio-economic dilemma of exploiting natural resources for the benefit of societies is ameliorated while maintaining an ecosystem balance.