Dramatic population growth in recent decades coupled with record-breaking droughts in parts of the West, have intensified demand for this naturally scarce resource. Pollution further compromises water supplies and increase costs to consumers as more water treatment becomes necessary to make contaminated water safe for human consumption and agricultural use.
Acid mine drainage is the primary source of water pollution from mining. Mining unearths large amounts of ore that contains precious metals, such as gold and silver, as well as iron and other sulfides. When sulfides in the ore are exposed to water and air, sulfuric acid is created, which can seep from mines and waste rock piles into streams, rivers, and groundwater.
This seepage is called acid mine drainage. Acid mine drainage is still seeping from mines in Europe that were worked by Romans prior to A. Chemicals used to separate valuable metals and minerals from ore also may leak into streams, rivers, and groundwater. Some of these chemicals, such as mercury, persist in the environment for decades. Although no longer used in mining, mercury continues to contaminate waterways.
Cyanide, which is widely used in modern gold mining, is another potentially deadly chemical that can get into water supplies. Mining can deplete surface and groundwater supplies.
Groundwater withdrawals may damage or destroy streamside habitat many miles from the actual mine site. Hundreds of tons of rock are unearthed, moved, and crushed in mining operations significantly increasing the amount of dust and particulates in the air. The mining industry has argued that submarine tailings disposal STD , which disposes of tailings in the sea, is ideal because it avoids the risks of tailings ponds; although the practice is illegal in the United States and Canada, it is used in the developing world.
The waste is classified as either sterile or mineralised, with acid generating potential, and the movement and storage of this material forms a major part of the mine planning process.
When the mineralised package is determined by an economic cut-off, the near-grade mineralised waste is usually dumped separately with view to later treatment should market conditions change and it becomes economically viable. Civil engineering design parameters are used in the design of the waste dumps, and special conditions apply to high-rainfall areas and to seismically active areas. Waste dump designs must meet all regulatory requirements of the country in whose jurisdiction the mine is located.
It is also common practice to rehabilitate dumps to an internationally acceptable standard, which in some cases means that higher standards than the local regulatory standard are applied.
Figure 1. Opencut coal mine loadout station and reclaimed land at the North Antelope Rochelle coal mine in Wyoming, United States. After mining finishes, the mine area must undergo rehabilitation. Waste dumps are contoured to flatten them out, to further stabilise them. If the ore contains sulfides it is usually covered with a layer of clay to prevent access of rain and oxygen from the air, which can oxidise the sulfides to produce sulfuric acid, a phenomenon known as acid mine drainage.
This is then generally covered with soil, and vegetation is planted to help consolidate the material. Eventually this layer will erode, but it is generally hoped that the rate of leaching or acid will be slowed by the cover such that the environment can handle the load of acid and associated heavy metals.
There are no long term studies on the success of these covers due to the relatively short time in which large scale open pit mining has existed. The dumps are usually fenced off to prevent livestock denuding them of vegetation. The open pit is then surrounded with afence, to prevent access, and it generally eventually fills up with ground water.
Brine mining involves extracting and evaporating the brine solutions to remove harmful elements and compounds Gruber et al. The drilling and transport of brine solutions can disrupt existing ecosystems and well casings, pipelines, and storage tanks are subject to corrosion due to the high salinity content of the solutions that they are exposed to, which can lead to leaks and contamination of adjacent bodies of water New York State Division of Mineral Resources, Currently, there is no economically plausible plan to clean up contamination of an aquifer by sodium chloride and harmful concentrations of chloride inhibit plant growth and can cause fish kills Division of Mineral Resources, All REE-bearing minerals contain low levels of the radioactive isotopes that can become concentrated in mine tailings.
Radionuclides are released as dust during mining or from exposed waste rock stockpiles where they are least containable and mostly airborne. Radiation can also leak into the ground, and nearby water sources after they have been separated into tailings, if the tailings are not stored safely. When companies break up materials during mining, the dust can release a variety of heavy metals commonly associated with health problems.
Another example of harmful dust generated is flue dust, a byproduct of mining fluorine. The following chart details how these contaminants enter the environment during mining and refining. Current mining and refining techniques make contaminant release common. Note: the two columns that involve waste rock and the column labeled, "No site rehabilitation after cease of mining operation" all involve mining specifically.
In addition to the issues addressed above, there are many other environmental issues associated with mining:. Mining, like most heavy industries, is dependent on fossil fuels, which generate the energy needed to operate a mine.
To combat these carbon emissions, some countries have enacted regulations requiring emission credits, but many countries do not have codes dealing with carbon output "Molycorp, inc. Some form of environmental standards are needed for larger countries like China and Russia, and other developing countries that mine large volumes of strategic minerals. Erosion and endangered species habitat. Mining is an inherently invasive process that can cause damage to a landscape in an area much larger than the mining site itself.
The effects of this damage can continue years after a mine has shut down, including the addition to greenhouse gasses, death of flora and fauna, and erosion of land and habitat. Most modern mining techniques have high water demands for extraction, processing, and waste disposal.
Wastewater from these processes can pollute water sources nearby and deplete freshwater supplies in the region surrounding the mine. Some mines, such as the Mountain Pass mine in southern California, have implemented waste-water recycling technologies, resulting in a huge decrease in water demands and liquid waste Molycorp, We have compiled three short case studies of environmentally-harmful mines, to illustrate the results on the environment and surrounding community of poorly regulated or monitored mines.
Greenland Minerals and Energy Ltd, based out of Australia, planned to open a mine in Greenland in However, the tailings disposal plan involved storing tailings in the Taseq lake, which will cause pollution of not only the lake, but the rivers leading from it and the ocean beyond. Fluorine, heavy metals, and radioactive decay products would all be introduced into the lake by these tailings Schuler et al, Due to the lack of environmental regulations from Denmark, the country overseeing the project, plans for the mine continue to move forward, despite the harmful effects it would have on the environment and the surrounding community.
Current estimates state that around 20, tons of REEs are illegally mined and exported from "off-grid" mines in China every year. It is unlikely that any of these illegal mines have environmental safeguards in place, which means that contamination, dust, and other wastes are not being addressed. This affects the health of the workers as well as destroys the surrounding environment Schuler et al, In , Molycorp had a problem with its waste disposal at Mountain Pass, when a pipeline leading out to evaporation ponds in the desert burst, spilling radioactive and toxic waste onto the desert floor Danelski, The resulting uncovering of past spills, coupled with economic factors, caused the shutdown of Mountain Pass and a complete reworking of their environmental practices.
However, the damage was done and the area and surrounding water sources are affected, perhaps permanently. Case studies like these illustrate the result of ignoring the environmental damages of mining, and leaving them unaddressed or unregulated.
Mission 's plan would address these issues. See the green mining page for more information. If no action is taken to remediate the many environmental problems inherent to modern mining, the end cost for governments and communities would be devastating.
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