Acid mine drainage is a type of pollution caused when acidic water flows out from a mine, construction site, or another disturbed area. Technically, the outflow of acidic water is natural in regions where acidic materials come into contact with the water table, but human activity can exacerbate the problem, creating a significant environmental situation. AMD, as it is also called, can degrade water and soil quality, pose a threat to native flora and fauna, and degrade human quality of life as well.
One of the primary sources of acid mine drainage is abandoned coal mines, some of which are centuries old. Acid mine drainage is also associated with some abandoned metals extraction sites. Typically, the dissolved water includes a great deal of iron and sulfuric acid, which turns the water a rich red to yellow color, making it quite distinctive and very visible. As the water flows out of the mine, it trickles into waterways, percolates through the soil, and enters the water table, causing widespread contamination.
In many nations, government oversight of abandoned mines is relatively recent, and in some cases, the responsible party may not be easily identified. For example, if a coal mine was abandoned in the 1700s, the mine's owners are obviously long-dead, and it may be tricky to find responsible descendants. More modern mines are sometimes protected through laws which the mining industry itself lobbied for, making it impossible to force the owners to rectify the situation.
There are several ways to address acid mine drainage. Sometimes, a buffer zone of a neutralizing material will do the trick, trapping the pollution and cleaning up the water and surrounding area. Managed wetlands also appear to be useful, because wetlands are like giant natural filters. It is also possible to aerate the site to reduce AMD, and sometimes filtering systems can be set up to allow heavy particles to settle to the bottom of the water, while clean water flows out of the filtering system.
In addition to acid mine drainage, it is also possible to find its opposite, alkaline mine drainage. Both types of pollution can create a major environmental threat, especially on the site of a mine emitting other forms of pollution. Sometimes, the cost of cleanup is so expensive that governments are forced to do nothing, despite the creation of government funds which are designed to deal with ecological disasters.