Assessing phytoremediation potentials of selected plant species in restoration of environments contaminated by heavy metals in gold mining areas of Tanzania

This study assessed and classified the phytoremediation potentials of selected plant species around gold mining areas in restoring the environments contaminated by heavy metals. The geographic focuses of the study were the Golden Pride Gold Mine (GPGM) and Geita Gold Mine (GGM) in Tanzania. The shoots and roots of plant species surrounding the mining areas and the samples of associated soils were collected and analysed for total concentrations of lead (Pb), chromium (Cr), cadmium (Cd), copper (Cu), arsenic (As), manganese (Mn) and nickel (Ni) using Atomic Absorption Spectrophotometer (AAS) and UV-VIS spectrophotometry. Results indicated that the soils from study areas were loamy textured and slightly acid (pH 6.1–6.5), soil organic carbon and organic matter were low (0.6–2.0%), total nitrogen was very low (<0.10%), phosphorous ranged from low (6–12 mg kg(−1) soil) to high (13–25 mg kg(−1) soil), and cation exchange capacity ranged from low (6.0–12.0 cmol((+)) kg(−1) soil) to medium (12.1–25.0 cmol((+)) kg(−1) soil). In assessing heavy metals using plant parts, the roots of giant rats-tail grass (Sporobolus pyramidalis) accumulated highest Pb (757.78 μg g(−1)), Creeping Blepharis (Blepharis maderaspatensis) the Cd (158.11 μg g(−1)), lantana (Lantana camara) the As (68.61 μg g(−1)), and leuceana (Leucaena leucocephala) accumulated higher Mn (2734.61 μg g(−1)) and Ni (4464.33 μg g(−1)). In shoots, L. leucocephala accumulated higher Cr (1276.67 μg g(−1)) and higher Cu (2744.44 μg g(−1)) in L. camara. Although S. pyramidalis, M. repens, L. camara, B. maderaspatensis and L. leucocephala are likely to pose hazards to herbivores (grazing animals) while entering the food chain, they are still potential hyperaccumulators thus can be used to decontaminate metalliferous affected soils. Blepharis maderaspatensis has never been reported anywhere as Pb, Cd, Cu, Mn and Ni uptake plant hence this can be regarded as a new finding.