Trace Elements Contamination of Kilembe Copper Mine Catchment Soils in Kasese District, Western Uganda

ABSTRACT

The mining and processing of copper in the Kilembe area, Western Uganda from 1956 to 1982 left behind several tailing sites containing cupriferous and coralliferous pyrites. A study was conducted to establish the concentrations of trace elements in point sources (tailings) within Kilembe mine and the distribution of trace elements within catchment soils. Mine tailings and catchment soils were sampled, acid digested and tested for elemental concentrations using ICP-MS. Tailings appeared to be the main sources of trace element contamination of soils with very high concentrations (mg kg⁻¹) of Cu (240–11500), Co (101–180) and Ni (140–248) compared with average world crust concentration of Cu (20–75), Co (1–15) and Ni (20) mg kg⁻¹. The concentration (mg kg⁻¹) of Cu (3.5–975), Co (4.9–110) and Ni (5.3–180) in soils along the mine zone and downstream were significantly higher than upstream trace element concentrations and in many samples exceeding recommended agricultural thresholds. Positive and significant correlations were observed between Fe and Mn with all trace elements in soil, suggesting adsorption and co-precipitation processes. The major factors influencing trace element distributions in the soils were distances and locations relative to point sources of contaminants, with soils close to and downhill of tailing sites more contaminated with trace elements. Remediation of soils to reduce trace elements is recommended in addition to containment of tailing erosion.

KEYWORDS:

• Mining
• tailings
• soil contamination
• erosion

Acknowledgments

This study was funded by the Carnegie Corporation New York through Makerere University Graduate School- NGAA II Grant. Prof. Scott Young and Dr. Liz Bailey, School of Biosciences Nottingham University provided technical guidance.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The dataset for this publication can be availed when the manuscript has been approved for publication or at any time that it is requested from the corresponding author.

Additional information

Funding

The work was supported by the Carnegie Corporation New York [NGAA II].