Abstract
Zambia’s Kabwe mine wastes (KMWs) are responsible for contaminating the surrounding soil and dust in the Kabwe district. Unfortunately, these wastes arise from the historical mining activities of lead (Pb) and Zinc (Zn), which lacked adequate waste management strategies. As a result, potentially toxic elements (PTEs) (Pb and Zn) spread across the Kabwe district. To assess the soil pollution derived from previous mining activities, we studied topsoil samples (n = 8) from the school playground soils (SPs). In this study, the degree of contamination, geochemical partitioning, and leachability, coupled with the release and retention of Pb and Zn, were studied. The SPs were classified as extremely enriched (EF > 40) and contaminated with Pb (Igeo > 5). On average, Pb (up to 89%) and Zn (up to 69%) were bound with exchangeable, weak acid-soluble, reducible and oxidizable phases, which are considered as ’geochemically mobile’ phases in the environment. The leachates from the soils (n = 5) exceeded the Zambian standard (ZS: 190:2010) for Pb in potable drinking water (Pb < 0.01 mg/L). Furthermore, the spatial distribution of Pb and Zn showed a significant reduction in contents of Pb and Zn with the distance from the mine area.
Highlights
Kabwe is a district in the central province of Zambia, which has geology dominated by carbonate-hosted Pb-Zn deposits [1]
The school playground soils (SPs) were classified according to the United States Department of Agriculture (USDA) soil classification, as either sandy loam (S1, S5, S6, and S7), silt loam (S3, S4, and S8), or loam (S2) (Table S1)
The discrepancies in the contents and leaching of Pb and Zn in the SPs might be attributed to the volume of aerosols deposited, particle size distribution and environmental conditions controlling the mobilities of the potentially toxic elements (PTEs)
Summary
Kabwe is a district in the central province of Zambia, which has geology dominated by carbonate-hosted Pb-Zn deposits [1]. Kabwe town is considered one of the most polluted cities globally due to the historical mining of lead (Pb) and Zinc (Zn) [2]. Mining activities between 1902 and 1994 produced approximately 0.8 Mt and 1.8 Mt of Pb and Zn, respectively [3]. The deposits are composed of massive sulfides ore bodies surrounded by secondary mineralization oxide zones of silicate ore (willemite; Zn2 SiO4 ), cerussite (PbCO3 ), quartz (SiO2 ), smithsonite (ZnCO3 ), goethite (FeOOH), hematite (Fe2 O3 ), and metal-bearing; vanadates, phosphates, carbonates of Zn, Pb, and V [1,3]. 90 years of mining without any environmental regulations, mining activities ceased in 1994 due to the depletion of the mineral resources.
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