Contribution of early succession regeneration plants to heavy metal remediation in abandoned Artisanal small-scale mining sites in Ghana

Abstract

Artisanal Small-Scale mining (ASM) is a major land use activity in Ghana. Despite its tremendous contribution to livelihoods, ASM is largely unregulated in the country, illegally operated, leaving most mined out sites unrehabilitated. In this study, we explored the extent to which early succession naturally regenerating plants on two abandoned illegal artisanal small scale mined-out sites (Chamfi and Alluvial types) remediate heavy metals. The study was undertaken in three districts of the Western Region of Ghana. Plots were randomly established in the alluvial, chamfi and reference (control) sites. Within each plot, samples of soil and naturally regenerating plants were collected for determination of bioaccumulation potential, translocation and contamination factor of cadmium (Cd), arsenic (As), lead (Pb), and mercury (Hg) using the Atomic Absorption Spectrophotometer. The results revealed that the concentration of As, Cd, Hg, Pb from soil samples, as well as roots and shoots of the plants collected from the two mined sites were significantly higher than the concentrations in the samples from the control plots. Our results show that heavy metal removal is more significant in plants at the alluvial mined soils than those at the chamfi sites. C. pubescens, C. odorata, and M. pudica were observed to be better cadmium translocators than the other vegetations sampled. Furthermore, plants at the alluvial sites recorded higher Bioaccumulation Factor (BF) in the roots than those at the chamfi sites for lead and arsenic. The study implies that natural regeneration of early successional species can promote contaminant removal on abandoned artisanal mine sites. They however vary in their capacity to accumulate different metals on abandoned soils. Within the context of illegal ASM prevalence, our results suggest that efforts should be made to encourage and minimize disturbances to the growth of early succession plant species as short-term alternative measures in abandoned artisanal mined sites, where reclamation is often neglected.