Acid Mine Drainage
AMD severely degrades water quality, and can kill aquatic life and make water virtually unusable.
Acid Rock Drainage (ARD) is a natural process whereby sulphuric acid is produced when sulphides in rocks are exposed to air and water. Acid Mine Drainage (AMD) is essentially the same process, greatly magnified.
When large quantities of rock containing sulphide minerals are excavated it reacts with water and oxygen to create sulphuric acid. When the water reaches a certain level of acidity, a naturally occurring type of bacteria called Thiobacillus ferroxidans may kick in, accelerating the oxidation and acidification processes, leaching even more trace metals from the wastes.
The acid will leach from the rock as long as its source rock is exposed to air and water and until the sulphides are leached out – a process that can last hundreds, even thousands of years. The acid is carried off the mine site by rainwater or surface drainage and deposited into nearby streams, rivers, lakes and groundwater.
Once it starts, AMD can effectively sterilize an entire water system for generations to come – turning it into a biological wasteland and a huge economic burden.
Acid Mine Drainage it is the biggest threat to waterways from mining. It creates low pH conditions that accelerate the heavy metal contamination and leaching process.
Acid mine drainage may be released from any part of the mine where sulfides are exposed to air and water, including waste rock piles, tailings, open pits, underground tunnels, and leach pads.
Acid mine drainage is responsible for physical, chemical, and biological degradation of stream habitat. It jeopardizes not only fish, but also the animals who feed on them.
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BC Wild, Environmental Mining Council of BC (2006). “Acid Mine Drainage: Mining and Water Pollution Issues“
Jennings, S.R., Neuman, D.R. and Blicker, P.S. (2008). “Acid Mine Drainage and Effects on Fish Health and Ecology: A Review“. Reclamation Research Group Publication, Bozeman, MT.