AMD: source and science
September 30, 2009
By INGI SALGADO
Acid mine drainage (AMD) started in the bowels of Johannesburg and Mpumalanga after water met exposed ore from abandoned mining operations.
This hard rock is rich in pyrite, an iron and sulphur compound. Ore exposure to water and oxygen produces bacteria that attack the pyrite, creating sulphuric acid that releases compounds from the rock and increases bacterial activity. As water levels have risen in the mining voids, the dissolved heavy metals and sulphates have crept closer to the surface of the earth.
In Johannesburg, the problem is compounded by easily eroded dolomitic rock below the surface, as well as levels of uranium, some radioactive. At the dolomitic level, AMD spreads in underground aquifers and waterways. At the surface, it flows into rivers and wetlands.
In addition to AMD, Mpumalanga has to contend with acid rain from burning coal. - Ingi Salgado
To read more stories on this topic follow the following links:
Downstream industries hit
Small firms, big headaches
Arguing over responsibility
Acid mine water is a ticking bomb
Mines aim to turn pollution into profit
Study looking into coal mining and water quality:
Coal mining on the Highveld and its implications for future water
quality in the Vaal River system - click here to download full document
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