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.

Novelty statement

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.

Keywords:

• Elements
• forage
• Kilembe mine
• toxicity
• trace

Acknowledgments

The author acknowledge Prof. Scott Young and Dr. Liz Bailey of The School of Biosciences, Nottingham University, UK, for providing technical support.

Authors’ contributions

Dr. Abraham R. Mwesigye was the lead person involved in proposal development, data collection, analysis and manuscript development. He was also the person awarded the grant to undertake the study. Dr. Edward Mwavu participated in data analysis and manuscript development and revisions.

Availability of data and materials

Data will be available on request, when the manuscript is approved for publication.

Consent to participate

This particular aspect of the research involved no human subjects as participants, volunteers or respondents and there was no need to seek consent to participate

Consent to publish

I consent to this work being published in the journal of submission

Disclosure statement

There are no competing interests through funding or any other way which could influence the content of this manuscript.

Ethical approval

The project proposal protocol was approved by the Uganda National Council of Science and Technology.

Additional information

Funding

This study was funded by Carnegie Corporation, New York, through Makerere University Graduate School NGAA II Project.