Analysis of the status and ecological risks of heavy metals contamination in artisanal and small-scale gold mine-spoils at the Atewa Forest Landscape, Ghana

Abstract

The study analysed the contamination status and potential ecological risk of heavy metals (Fe, Cu, Mn, Zn, Pb, Cd, As and Hg) in soils from un-reclaimed illegal artisanal and small-scale gold mine (‘galamsey’) sites at the Atewa forest landscape. Composite soil samples (48) were collected from topsoil (0–20 cm) and subsoil (20–50 cm) across eight communities in four districts. Samples were analyzed using FAAS in the laboratory, and the results were evaluated using the geoaccumulation index (Igeo) and potential ecological risk index (PERI). The results based on the I geo values showed that the contamination status from the heavy metals in the topsoil and subsoil were: Hg>Cd>As>Pb>Mn>Cu>Zn>Fe and Hg>Cd>As>Pb>Cu>Mn>Zn>Fe respectively. These suggest strong Hg pollution in both topsoil (4.01) and subsoil (4.45), moderate Cd contamination in topsoil (1.04) and subsoil (1.48) and moderate As (0.54) contamination in subsoil only. The PERI from the heavy metals in both topsoil and subsoil were: Hg>Cd>As>Pb>Cu>Mn>Zn>Fe. Overall, Hg (PERI > 964) posed very severe ecological risk, with the greatest contribution to potential ecological toxicity; followed by Cd (PERI > 92) and As (PERI > 16) in the soils. Multivariate statistical analysis revealed that the elements Fe, Cu, Mn were consistently naturally occurring in the soil minerals while As, Pb and Hg were of anthropogenic origin, notably galamsey’ activities with Cd and Zn originating from both sources. This outcome highlights the need for prompt action towards the restoration of soil quality in the study area to protect human and ecological health and enhance post-mine forest restoration.