Send to a friend
[WINDHOEK] Agricultural soils near mining sites have high amounts of heavy metals such as lead and copper, thus posing danger to human health and the environment, a study in Namibia says.
Scientists from the University of Namibia (UNAM) and the University of Zagreb in Croatia evaluated the types of heavy metals present in Kombat mine — a site used for mining copper in northern Namibia between 1962 and 2008 — and its surroundings to determine if they posed risk to humans.
They selected 14 samples of soil from a dam at the mining site, 13 soil samples from an area near the mine and 20 soil samples in a site relatively far from the mine. The soil samples were selected twice, each in March and in August 2006. The amounts of heavy metals in the mining site were then compared with the surrounding areas.
“In many Sub-Saharan Africa countries, [sufficient] science-based evidence is needed to influence policies that contribute to reducing the adverse effects of mining activities on the ecosystem and promote safe mining among various stakeholders, including local communities.”
Felix Toteu, UNESCO
The study, published in the Journal of Geochemical Exploration on 21 January, found up to 150 milligrams of copper and 164 milligrams of lead for each kilogram of soil near the mine. The amounts are higher than Canadian guidelines for agricultural use: 63 milligrams copper and 70 milligrams lead for each kilogram of soil.
“While heavy rain can cause a collapse of the tailings [mine waste], even a slight breeze can freely spread loosely deposited fine-grained toxic materials in the surrounding area and pose arable soil contamination as well as health risk in [the] residential area,” the authors explain.
Benjamin Mapani, a geologist at UNAM and a co-author of the study, says if some of these metals persist in the environment they can contaminate crops and enter the food chain. The study recommends covering the affected areas with uncontaminated soil so that children do not inhale polluted dust, relocating people from affected areas, and growing certain grasses that take up the metals.
There are many abandoned mines in southern Africa but few studies have been conducted to determine their impact on the environment, according to Mapani.
Mapani, who is also the secretary-general of the Geological Society of Africa, adds that the UNESCO office in Nairobi, Kenya, has developed a project since 2013 to study the problem in Sub-Saharan Africa.
The scoping phase involves Burkina Faso, Cameroon, Democratic Republic of Congo, Kenya, Namibia, Nigeria, Senegal, South Africa and Zambia.
Felix Toteu, coordinator of the UNESCO project, says they expect that during the next four years, the project will cover more countries and more types of mine waste including coal, uranium, nickel, cobalt and oil.
He says that Africa will suffer from contamination-related diseases if nothing is done now. The project aims at collecting scientific data on the impacts of mining on the environment.
“In many Sub-Saharan Africa countries, [sufficient] science-based evidence is needed to influence policies that contribute to reducing the adverse effects of mining activities on the ecosystem and promote safe mining among various stakeholders, including local communities,” Toteu tells SciDev.Net.
Link to the abstract in the Journal of Geochemical Exploration
This article has been produced by SciDev.Net's Sub-Saharan Africa desk.