Crop uptake of heavy metals in response to the environment and agronomic practices on land near mine tailings in the Zambian Copperbelt Province

Kaninga, Belinda; Lark, R. Murray; Chishala, Benson H.; Maseka, Kakoma K.; Sakala, Godfrey M.; Young, Scott D.; Tye, Andrew; Hamilton, Elliott M.; Watts, Michael J.

Abstract

© 2021, The Author(s), under exclusive licence to Springer Nature B.V. part of Springer Nature. A field experiment was undertaken on farmers’ fields adjacent to a large mine tailings dam in the Zambian mining town of Kitwe. Experimental plots were located close to the tailings (≤ 200 m) or further away (300–400 m) within the demarcated land farmed by the same community. This study evaluated the uptake of Cd, Cu, Ni, Pb and Zn by pumpkin leaves and maize grown in soil amended with lime and manure applied at agronomic rates, and the subsequent risk of dietary exposure to the local community, typical of many similar situations across the Zambian Copperbelt. Treatments, combinations of lime and manure (present or absent), were applied to subplots selected independently and randomly within each main plot, which represented variable geochemistry across this study site as a result of windblown/rain-driven dust from the tailings. Total elemental concentrations in crops were determined by ICP-MS following microwave-assisted acid digestion. Concentrations of Cu and Pb in pumpkin leaves were above the prescribed FAO/WHO safe limits by 60–205% and by 33–133%, respectively, while all five metals were below the limit for maize grain. Concentration of metals in maize grain was not affected by the amendments. However, lime at typical agronomic application rates significantly reduced concentrations of Cd, Cu, Pb and Zn in the pumpkin leaves by 40%, 33%, 19% and 10%, respectively, and for manure Cd reduced by 16%, while Zn increased by 35%. The uptake of metals by crops in locations further from the tailings was greater than closer to the tailings because of greater retention of metals in the soil at higher soil pH closer to the tailings. Crops in season 2 had greater concentrations of Cu, Ni, Pb and Zn than in season 1 due to diminished lime applied only in season 1, in line with common applications on a biannual basis. Maize as the staple crop is safe to grow in this area while pumpkin leaves as a readily available commonly consumed leafy vegetable may present a hazard due to accumulation of Cu and Pb above recommended safe limits.

Citation

Kaninga, B., Lark, R. M., Chishala, B. H., Maseka, K. K., Sakala, G. M., Young, S. D., …Watts, M. J. (2021). Crop uptake of heavy metals in response to the environment and agronomic practices on land near mine tailings in the Zambian Copperbelt Province. Environmental Geochemistry and Health, 43(9), 3699-3713. https://doi.org/10.1007/s10653-021-00849-7

• Journal Article Type: Article
• Acceptance Date: Jan 29, 2021
• Online Publication Date: Mar 9, 2021
• Publication Date: 2021-09
• Deposit Date: Nov 3, 2023
• Journal: Environmental Geochemistry and Health
• Print ISSN: 0269-4042
• Electronic ISSN: 1573-2983
• Publisher: Springer Verlag
• Peer Reviewed: Peer Reviewed
• Volume: 43
• Issue: 9
• Pages: 3699-3713
• DOI: https://doi.org/10.1007/s10653-021-00849-7
• Keywords: Geochemistry and Petrology; General Environmental Science; Water Science and Technology; Environmental Chemistry; General Medicine; Environmental Engineering
• Public URL: https://nottingham-repository.worktribe.com/output/5407923
• Publisher URL: https://link.springer.com/article/10.1007/s10653-021-00849-7
• Additional Information: The authors declare that there were no competing or conflicting interests.; : This manuscript has been approved by the authors and is submitted with the permission of the Executive Director of the British Geological Survey.