Evaluation of Dispersion of Lead-Bearing Mine Wastes in Kabwe District, Zambia

Narrative review of lead poisoning in humans caused by industrial activities and measures compatible with sustainable industrial activities in Republic of Zambia

Lead (Pb) pollution and human exposure to Pb, is an important issue for the international community to address being associated with 0.90 million deaths from long-term effects. The Republic of Zambia is a typical mineral resource-rich country, with long-standing mining and smelting activities of metals including Pb in several parts of the country. This narrative review provides a comprehensive overview of previous papers that have assessed human exposure to Pb and related health effects in Zambia. Environmental remediation methods that should be applied locally, ways to reduce Pb exposure of the population, and issues that need to be addressed by various sectors are discussed. Environmental remediation methods using locally available and affordable materials are needed to ensure both sustainable industrial activities and pollution prevention. In the Zambian mining towns, including Kabwe, various research activities have been conducted, including environmental monitoring, human biomonitoring and health impact assessments. The town of Kabwe, which was one of Zambia's largest Pb mining area in the 20th century, continues to have formal and informal Pb-related industries and is known as one of the most polluted areas in the world. For example, despite the World Health Organization asserting that "For an individual with a blood Pb concentration ≥ 5 μg/dL, appropriate action should be taken to terminate exposure", there are reports of blood Pb levels in Kabwe children exceeding 100 μg/dL. While Pb pollution is a global issue, not many places have such continuous and comprehensive research has been conducted, and there is much to be learned from the knowledge accumulated in these areas. Because the high levels of Pb accumulation in humans and the adverse health effects were clarified, we consider that it is important to combine mining activities, which are a key industry, with measures to prevent environmental pollution.

Impacts of Surface Water on Windborne Lead Dispersion from the Zinc Plant Leach Residue in Kabwe, Zambia

Effects of the water content of ground surface on windborne lead (Pb) dispersion from the zinc (Zn) leach residue site at the Kabwe mine, Zambia, were simulated. The Pb-bearing Zn plant leach residue site was selected as the source of the dispersion, and water conditions of the surface of the source were evaluated by the modified normalized difference water index (MNDWI) under the actual weather conditions in the year 2019. The MNDWI was calculated based on Sentinel-2 datasets, which were acquired in the year 2019. The index was used for monitoring the surface condition of the source necessary for simulating Pb dispersion, because the higher surface water content reduces the intensity of windborne source. The results showed that the wind speeds and directions had huge impacts on Pb dispersion when the MNDWI had negative values, and that the dispersion was inhibited when the MNDWI had positive values. These indicate that the water content of the surface is sensitive to dispersion, and that MNDWI is an effective parameter that expresses the source strength.

Solid-Phase Partitioning and Leaching Behavior of Pb and Zn from Playground Soils in Kabwe, Zambia

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 (I_geo > 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.