Regardless of the substance mined, a wide range of damage and pollution is typically incurred, ranging in size and intensity from very local and low impact to the destruction of whole ecosystems, landscapes, and human
Table 1 Examples of damage and pollution of mining-impacted landscapes and ecosystems
Solid wastes Water
Gaseous pollutants Dust blows
To access deposits, removal and/or improper storage of top soil
May be low in nutrients due to extraction process Acid mine drainage
Discharge of groundwater pumped from mines
Release of metals, mobilization
Open cast mining may leave large pits, remove mountain sides, relocate villages Subsurface mining may lead to accumulation of mine wastes, such as slag heaps or tailings impoundments, on the surface
Dispersal of pollutants, e.g., mercury from gold mining Dispersal of dust and toxic substances into the food chain, respiratory diseases in humans and animals Remediation is hampered -topsoil may have to be brought in from elsewhere Very difficult for plants to colonize Reduction in pH, locally severe, mobilization of metals, death of organisms Changes in hydrology may lower water table or change direction of groundwater flow, may extend across a large area (in the order of kilometers) Changes in organism populations, toxins into the food chain Changes in hydrology, esthetic value, destruction of whole ecosystems Large areas may be left barren communities (Table 1). Examples of the latter can be found in the Rhineland region, an area of about 2500 km2 west of Cologne in Germany. Open cast lignite mines, several kilometers in length, up to a kilometer in width, and up to 500 m deep, slowly move through the landscape. Topsoil, rock, and lignite are removed on one side. After extraction of the lignite, the remaining materials are deposited on the other. In the process, the mines have displaced whole villages in their path. However, these mines also provide some of the best examples of restoration - after the mine has passed through, not only is the landscape reconstructed, but so are the villages.
Mines cause habitat destruction while the wastes, such as slag heaps and tailings, form substrates that are typically poor in nutrients, high in potentially toxic substances, and that poorly retain water. Such substrates are not easily colonized by organisms, particularly higher plants. Around the world, mine wastes can be found that have been devoid of vegetation for decades, sometimes centuries. This is not necessarily due to toxicity, but to the poor water holding capacity and low concentrations of available nutrients. Such wastes are not stable and therefore cause problems to the surrounding ecology, including humans through erosion into surface waters, dispersal as dust blows, or leaching and acid mine drainage. Over the past century or so, this led to the realization that the problems associated with mining must be remedied.
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