Forage accumulation of potentially toxic elements (PTEs) from soils around Kilembe copper mine, Western Uganda.

ABSTRACT

Past copper mining within Kilembe valley between 1956-1982 left behind mine tailings rich in potentially toxic elements (PTEs). This study was conducted to assess the concentrations of PTEs in soils and the potential uptake by forage. Tailings, soils and forage were collected and analyzed using ICP-MS. The study established that over 60% of grazed plots contained high concentrations of Cu, Co, Ni and As. Copper in 35%, Co in 48% and Ni in 58% of forage soil plots exceeded the thresholds for agricultural soils. Bio-accumulation of Zn and Cu, was observed. Zinc in 14% of guinea grass (Panicum maximum), 33% coach grass (Digitalia Scarulum) and in 20% of elephant grasses (Penisetum perpureun) exceeded thresholds of 100-150 mg kg-1. Copper (Cu) concentrations in 20% of Penisetum perpureun and 14% of Digitalia Scarulum exceeded grazing thresholds of 25 mg kg-1. Containment of tailing erosion should be explored to control erosion of tailings into grazing areas.

This is the first study of this kind which has investigated forage uptake of trace elements from Kilembe contaminated soils and the possible risks for grazing animals. It is also the first study to profile the differences in bioaccumulation potentials of different species of forage. The study further identifies a forage species of guinea grass and couch grass as having bioremediation potentials for zinc contaminated soils.