275-5 Geogenic contamination of soil and groundwater in mining regions of Zambia

Session: Advancing the Understanding and Management of Groundwater Pollution with Arsenic and Other Geogenic Contaminants Using Geospatial Tools, Machine Learning, and Data Science, Part II

Presenting Author:

Kawawa Banda

Authors:

Banda, Kawawa¹, Chanda, Emmanuel², Chapewa, Desderius³, Bhattacharya, Prosun⁴, Olsson, Richard⁵, Ijumulana, Julian M.⁶, Kumar, Rakesh⁷

(1) Integrated Water Resource Management Centre, Department of Geology, School of Mines, University of Zambia, Lusaka, Lusaka, Zambia, (2) Department of Mining Engineering, University of Zambia, Lusaka, Lusaka, Zambia, (3) Geological Society of Zambia, Lusaka, Zambia, (4) KTH-International Groundwater Arsenic Research Group, Department of Sustainable Development, Environmental Science and Engineering, KTH Royal Institute of Technology, Teknikringen 10B, SE-114 28 Stockholm, Sweden, (5) Department of Fibre and Polymer Technology-Polymeric Materials, School of Chemical Science and Engineering, KTH Royal Institute of Technology, Teknikringen 56-58, Stockholm, Sweden, (6) KTH Royal Institute of Technology, Stockhom, Sweden; Department of Transportation and Geotechnical Engineering, College of Engineering and Technology, Dar es Salaam, Tanzania, (7) Department of Biosystems Engineering, Auburn University, Auburn, USA,

Abstract:

Geogenic contamination of soils and aquifers in Zambia’s mining regions, particularly the Copperbelt and Kabwe districts, presents a significant environmental and public health concern. The region’s complex geology, characterized by sulfide rich mineralization, granitic bedrock, and crystalline basement aquifers, naturally contributes elevated concentrations of trace elements often exhibiting depth-dependent distribution associated with groundwater flow and water-bedrock interactions. Their mobility in groundwater is influenced by geochemical factors such as pH buffering and redox conditions, while additional variability arises from anthropogenic sources like smelter emissions and tailings. Naturally elevated levels of arsenic (As) and fluoride (F⁻) in groundwater are of particular concern, especially from deep boreholes and fractured basement aquifers. Regional modeling estimates that over three million people in Zambia may be exposed to fluoride concentrations exceeding the World Health Organization guideline of 1.5 milligrams per liter. Similarly, arsenic concentrations in basement aquifers may pose chronic health risks, although detailed spatial mapping and speciation studies remain limited. Investigations in the Copperbelt and Eastern crystalline provinces indicate heightened vulnerability in areas underlain by granitic or mineralized lithologies. Groundwater in these areas often contains elevated iron, manganese, and other trace metals, reflecting redox conditions that facilitate arsenic mobilization via the reductive dissolution of iron three oxides. Fluoride is released from fluorite and apatite bearing minerals under alkaline conditions, particularly in calcium deficient groundwater. In contrast, surface soils and shallow groundwater in mining adjacent communities such as Kabwe, Kitwe, and Mufulira show highly elevated concentrations of lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn), often exceeding natural background levels by several orders of magnitude. These elevated concentrations are primarily attributed to anthropogenic sources, including smelter emissions, mine tailings, and atmospheric deposition of dust. Isotopic and spatial analyses in Makululu area of Kabwe district confirm that extreme Pb levels originate from historical industrial activity rather than from geogenic sources.

To effectively distinguish geogenic from anthropogenic contamination, comprehensive approaches including depth profile sampling, sequential extraction, and multi isotopic tracing are essential. Establishing natural geochemical baselines is crucial for accurate risk assessment, sustainable groundwater management, and targeted environmental protection in mining impacted regions. Addressing these often-overlooked geogenic hazards is key to protecting public health and enabling long term environmental remediation across the mining regions of Zambia.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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