Removal of selected heavy metals and metalloids from an artisanal gold mining site in Ghana using indigenous plant species

This study evaluated the hyperaccumulation potential of four indigenous plant species: Chromolaena ordorata (CO), Paspalum viginatum (PV), Chrysopogon zizanioides (CZ) and Cynodon dactylon (CD) using soil polluted by the illegal gold mining activities. Nine treatments were used in this study: Control, CO, CZ, PV, CD, CO+PV, CO+CD, CZ+PV and CZ+CD samples. The soils’ physico-chemical properties and the concentration of some selected heavy metals and metalloid (As, Cd, Cu, Ni and Pb) were determined. Plant growth and dynamics of pH, electrical conductivity and heavy metals and metalloid in the gold ore mined soil were monitored for nine weeks. Accumulation, bioaccumulation and translocation potentials were determined. The mined soil was loamy textured and acidic with pH ranging between 5.71 and 6.24. Soil organic carbon, total nitrogen and phosphorous contents were relatively low (0.21 %, 0.09 % and 4.79 mg/kg soil, respectively). Concentrations of Pb, Cu, Ni, As and Cd (40.22, 30.54, 23.58, 6.18 and 0.27 mg/kg, respectively) in the area were below the WHO permissible limits. CO+PV combination resulted in higher reductions in As, Cd, Cu, Ni and Pb (40.1, 53.1, 36.8, 29.3 and 41.2%, respectively) from the mined soil. All the investigated plant species recorded BR > 1 for Cd and BR < 1 for As, Cu, Ni and Pb. Therefore, all studied plant species are good phytoextractors for Cd.