Senegal (Kedougou) – Mercury in Artisanal Gold Mining
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Artisanal and small scale gold mining (ASGM) increased very much in West Africa when gold prices rose and thousands more poor people were drawn into the industry. ASGM frequently uses mercury in the process of extracting gold form ore and consequently large amounts of mercury are released, impacting miners, their families and the environment. Blacksmith supported an outreach programme which demonstrated efficient low mercury processes to isolated mining villages. Uptake of the improvements was high but considerable work remains to reach the many scattered mining communities in remote areas of the country.
The Tambacounda region was chosen as a pilot site for this project based on information and recommendations from the government of Senegal as well as substantial consensus on the assets of the region as is general knowledge in the international mining community.
Artisanal, or small scale gold mining (also called ASGM) is one of the most significant sources of mercury release into the environment in the developing world, with at least a quarter of the world’s total gold supply coming from such sources. ASGM miners combine mercury with gold-carrying silt. The gold and mercury combine to form an amalgam, making recovery of the gold easier. The amalgam is subsequently heated with blow torches or over an open flame so that the mercury burns off, and gold is left at a purity of 70 to 80 percent. The gaseous mercury is subsequently inhaled by the miners, or by their immediate family, including their children.
Mercury which is not inhaled during the amalgamation process settles into the surrounding environment, or circulates globally at regional and global scales for future deposition far from the site, where it is absorbed and processed by a variety of living organisms. As a consequence of its misuse, mercury amalgamation results in the discharge of an estimated 1000 tons of mercury per annum which represents about 30% of the world’s anthropogenic mercury releases. It is estimated that between 10 and 15 million artisanal and small scale gold miners worldwide, including 4.5 million women and 600,000 children.
This process transforms elemental mercury into methylmercury. Methylmercury is one of the most toxic organic compounds and a powerful neurotoxin that works its way up the food chain through bioaccumulation. According to UNIDO, as much as 95 percent of all mercury used in ASGM mining is released into the environment, constituting a danger on all fronts – economic, environmental and human health. There are a number of cleaner technology alternatives to current methods of mercury amalgamation. The use of retorts during the mercury burn-off stage is a simple and cost-effective way to decrease the occupational exposure to mercury and minimize its release into the environment. Retorts allow for the efficient capture and reuse of mercury.