Impact of different illegal Artisanal Small-Scale Mining techniques on soil properties in a major mining landscape in Ghana

Abstract

The widespread prevalence of illegal Artisanal Small-Scale Mining has raised significant concerns about its environmental and health impacts. This study investigates the effects of two mining methods (alluvial and chamfi) on soil physical, chemical, and microbial properties four years after mining in three municipalities of the Western Region of Ghana. The study identified four species of Aspergillus fungi (niger, flavus, ochraceous and fumigatus) and Trichoderma species in both mined and control soils. The quantity of A. fumigatus was significantly higher in control plots compared to mined plots. In alluvial sites, bacterial numbers were significantly higher in control plots than in mined plots, while in chamfi sites, bacterial numbers did not differ significantly between mined and control plots. Soil texture in both mined sites was predominantly sandy loam and loamy sand, with a generally high silt to clay ratio. Mined plots at both sites were significant and more acidic (p < 0.05) than the control plots. Additionally, cation exchange capacity (CEC), electrical conductivity (EC), organic carbon (OC), total nitrogen (TN), phosphorus (P), potassium (K⁺), calcium (Ca²⁺), and magnesium (Mg²⁺) levels were significantly higher in control plots compared to mined plots. The control plots also exhibited higher base saturation and lower exchangeable acidity than mined plots. Bacteria count at Chamfi sites was generally higher at mined areas than the control sites, with the reverse being the case for Alluvial sites. Soil chemical parameters were higher at control areas than at mined sites, irrespective of the mining approach used. However, there was no clear pattern of differences in soil chemical properties at Chamfi and Alluvial mined sites. This study provides insights and additional perspectives for improving decision-making and guiding the potential restoration of these areas.