Letters & Articles

MAFES: The International Network for Acid Prevention (INAP) - 03/14/13


When rock surfaces are exposed to air and rain, a reaction can occur with the elements in the rock which results in a change in the characteristics of the water that drains off. If the rock contains sulphides, a natural oxidation process can acidify the water.

This is known as acid drainage (also acid rock drainage (ARD) or acid mine drainage (AMD)). As the water becomes more acidic, its capacity to leach out other elements from the rock, such as metals, increases. The resulting drainage can become very acidic and contain a number of harmful constituents. In some cases, elements from the rock can leach out into contact water without acidification and result in water contamination – this is known as metal leaching (ML). In either case, polluted water drains away from the exposed rock and can have significant impacts on surrounding water bodies (rivers, lakes, coastal areas, groundwater) and the wildlife or people who come in contact with these sources.