Quantifying the local and downstream environmental impacts of artisanal and small-scale gold mining

BGS Research — Integrated resource management in Eastern Africa

Nam Lolwe, or Lake Victoria, and the rivers that feed into it, is an important source of drinking water and food for the densely populated rural region of south-west Kenya. The use of chemicals such as mercury and cyanide in artisanal and small-scale gold mining (ASGM) in this region is an environmental issue that is causing widespread contamination of the ecosystems of the lake basin. There is a need to understand the extent of the issue and develop sustainable best practices to mitigate the impact.

Gold panning with mercury
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Gold panning with mercury. BGS © UKRI.

Migori County is a major ASGM centre in south-west Kenya. Gold mining is focused on gold hosted by quartz–carbonate reefs in the basalts and the banded iron formations of the Precambrian Migori greenstone belt. Mining operations involve deep, unstable shafts, manual extraction and crushing followed by milling using Tanzanian-designed ball mills. The gold is concentrated using sluice boxes and then recovered from the concentrates using mercury. The mine tailings are sent to a cyanidation plant to remove the remaining gold.

Research for this project includes:

  • assessing the current gold mining practices with a view to eliminating the use of mercury
  • assessing the contamination of drinking water sources (such as boreholes and the water courses) to provide a better understanding of the extent of the contamination
  • tracing the migration of contamination along the water courses into Nam Lolwe

Ongoing research

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