Acid mine drainage (AMD), or acid rock drainage (ARD), refers to the outflow of acidic water from (usually) abandoned metal mines or coal mines. However, other areas where the earth has been disturbed (e.g. construction sites, subdivisions, transportation corridors, etc.) may also contribute acid rock drainage to the environment. In many localities the liquid that drains from coal stocks, coal handling facilities, coal washeries, and even coal waste tips can be highly acidic, and in such cases it is treated as acid rock drainage. Acid rock drainage occurs naturally within some environments as part of the rock weathering process but is exacerbated by large-scale earth disturbances characteristic of mining and other large construction activities, usually within rocks containing an abundance of sulfide minerals. An acid (often represented by the generic formula HA) is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a pH of less than 7. ... Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily forms positive ions (cations) and has metallic bonds. ... This article is about mineral extraction. ... Wyoming coal mine Coal mining is the mining of coal. ... Coal Coal (IPA: ) is a fossil fuel extracted from the ground by underground mining or open-pit mining (surface mining). ...

Occurrence

Sub-surface mining often progresses below the water table, so water must be constantly pumped out of the mine in order to prevent flooding. When a mine is abandoned, the pumping ceases, and water floods the mine. This introduction of water is the initial step in most acid rock drainage situations. Tailings piles or ponds may also be a source of acid rock drainage. Sub-surface mining or underground mining refers to a group of techniques used for the extraction of valuable minerals or other geological materials from the earth. ... Cross section showing the water table varying with surface topography as well as a perched water table The water table or phreatic surface is the surface where the water pressure is equal to atmospheric pressure. ... Tailings (also known as slickens[1]) are the waste left over[2] after removing the gangue from ore. ...

After being exposed to air and water, oxidation of metal sulfides (often pyrite, which is iron-sulfide) within the surrounding rock and overburden generates acidity. Colonies of bacteria and archaea greatly accelerate the decomposition of metal ions, although the reactions also occur in an abiotic environment. These microbes, called extremophiles for their ability to survive in harsh conditions, occur naturally in the rock, but limited water and oxygen supplies usually keep their numbers low. Special extremophiles known as acidophiles especially favor the low pH levels of abandoned mines. In particular, Acidithiobacillus ferrooxidans is a key contributor to pyrite oxidation [1]. The most fundamental reactions in chemistry are the redox processes. ... In chemistry, a sulfide (sulphide in British and Canadian English) is a combination of sulfur with an oxidation number of -2, with another chemical element or a radical thereof. ... This article is about the mineral Pyrite or Fools Gold. ... Overburden is the term used in mining to describe material that lies above the area of economic interest. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Phyla / Classes Phylum Crenarchaeota Phylum Euryarchaeota     Halobacteria     Methanobacteria     Methanococci     Methanopyri     Archaeoglobi     Thermoplasmata     Thermococci Phylum Korarchaeota Phylum Nanoarchaeota Archaea (; from Greek αρχαία, ancient ones; singular Archaeum, Archaean, or Archaeon), also called Archaebacteria (), is a major division of living organisms. ... An extremophile is an organism, usually unicellular, which thrives in or requires extreme conditions that would exceed optimal conditions for growth and reproduction in the majority of mesophilic terrestrial organisms. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... Acidophilic describes the tendency of a inorganic particle or organism to acidic conditions or acids. ... . The initial letter is shown capitalized due to technical restrictions. ...

Metal mines may generate highly acidic discharges where the ore is a sulfide or is associated with pyrites. In these cases the predominant metal ion may not be iron but rather zinc, copper, or nickel. The most commonly-mined ore of copper, chalcopyrite, is itself a copper-iron-sulfide and occurs with a range of other sulfides. Thus, copper mines are often major culprits of ARD. Iron ore (Banded iron formation) Manganese ore Lead ore Gold ore An ore is a volume of rock containing components or minerals in a mode of occurrence which renders it valuable for mining. ... An ion is an atom or group of atoms that normally are electrically neutral and achieve their status as an ion by loss or addition of one or more electrons. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Atomic mass 63. ... General Name, Symbol, Number nickel, Ni, 28 Chemical series transition metals Group, Period, Block 10, 4, d Appearance lustrous, metallic Atomic mass 58. ... Chalcopyrite (sometimes called peacock pyrite) is a copper iron sulfide mineral that crystallizes in the tetragonal system. ... Currently, the most common source of copper ore is the mineral chalcopyrite (CuFeS2), which accounts for about 50% of copper production. ...

Chemistry

The chemistry of oxidation of pyrites, the production of ferrous ions and subsequently ferric ions, is very complex, and this complexity has considerably inhibited the design of effective treatment options. Ferrous in chemistry is a term used for the iron with an oxidation number +2. ... Ferric is a term used for the iron with the oxidation number +3. ...

Although a host of chemical processes contribute to ARD, pyrite oxidation is by far the greatest contributor. A general equation for this process is:

2FeS₂(s) + 7O₂(g) + 2H₂O(l) → 2Fe²⁺(aq) + 4SO₄^2-(aq) + 4H⁺(aq)

The solid pyrite, when introduced to oxygen and water, is catalyzed to form Iron(II) ions, sulfate ions, and hydrogen ions. The hydrogen ions bind to the sulfate ions to produce sulfuric acid. In inorganic chemistry, a sulfate (IUPAC-recommended spelling; also sulphate in British English) is a salt of sulfuric acid. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Sulfuric acid (British English: sulphuric acid), H2SO4, is a strong mineral acid. ...

Effects

Effects on pH

In some ARD systems temperatures reach 120 degrees Fahrenheit (50 °C), and the pH can be as low as -3.6[2]. ARD-causing organisms can thrive in waters with pH very close to zero. Negative pH occurs when water evaporates from already acidic pools thereby increasing the concentration of hydrogen ions.

About half of the coal mine discharges in Pennsylvania have pH under 5 standard units. However, a significant portion of mine drainage in both the bituminous and anthracite regions of Pennsylvania is alkaline, because limestone in the overburden neutralizes acid before the drainage emanates. Wyoming coal mine Coal mining is the mining of coal. ... Official language(s) None Capital Harrisburg Largest city Philadelphia Area  Ranked 33rd  - Total 46,055 sq mi (119,283 km²)  - Width 160 miles (255 km)  - Length 280 miles (455 km)  - % water 2. ... Bituminous coal Bituminous coal is a relatively hard coal containing a tar-like substance called bitumen. ... Anthracite coal Anthracite (Greek Ανθρακίτης, literally a form of coal, from Anthrax [Άνθραξ], coal) is a hard, compact variety of mineral coal that has a high luster. ... World coal producers and consumers. ... Limey shale overlaid by limestone. ... Overburden is the term used in mining to describe material that lies above the area of economic interest. ... Neutralization is a chemical reaction, also called a water forming reaction, in which an acid and a base or alkali (soluble base) react and produce a salt and water. ...

ARD has recently been a hindrance to the completion of the construction of Interstate 99 near State College, but this ARD didn't come from a mine: pyritic rock was unearthed during a road cut and then used as filler material in the I-99 construction. Interstate 99 (abbreviated I-99) is a part of the U.S. Interstate highway system. ... Downtown State College, during 2005 Central Pennsylvania Festival of the Arts State College, Pennsylvania, is a borough -- and more generally used, the borough and surrounding townships -- in Centre County in the U.S. state of Pennsylvania. ...

Yellow boy

Yellow boy in a stream receiving acid drainage from surface coal mining.

When the pH of ARD is raised past 3, either through contact with fresh water or neutralizing minerals, soluble Iron(II) ions hydrolize to form Iron(III) hydroxide, a yellow-orange solid colloquially known as Yellow boy. Yellow boy discolors water and smothers plant and animal life on the streambed, disrupting stream ecosystems. The process also produces additional hydrogen ions, which can further decrease pH. Research is currently being conducted as to the feasibility of using Yellow boy as a commercial pigment. Download high resolution version (640x971, 334 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (640x971, 334 KB) Wikipedia does not have an article with this exact name. ... Neutralization is a chemical reaction, also called a water forming reaction, in which an acid and a base or alkali (soluble base) react and produce a salt and water. ... Iron(III) oxide-hydroxide (FeO(OH)), also called hydrated iron oxide and yellow iron oxide, is an oxide-hydroxide of iron. ... A running stream. ... An ecosystem, a contraction of ecological and system, refers to the collection of components and processes that comprise, and govern the behavior of, some defined subset of the biosphere. ...

Heavy metal contamination

Many acid rock discharges also contain elevated levels of toxic metals, especially nickel and copper with lower levels of a range of other heavy metal ions such as lead, arsenic, aluminium, and manganese. In the coal belt around the south Wales valleys in the UK highly acidic nickel-rich discharges from coal stocking sites have proved to be particularly troublesome. General Name, Symbol, Number lead, Pb, 82 Chemical series poor metals Group, Period, Block 14, 6, p Appearance bluish white Atomic mass 207. ... General Name, Symbol, Number arsenic, As, 33 Chemical series metalloids Group, Period, Block 15, 4, p Appearance metallic gray Atomic mass 74. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Atomic mass 26. ... General Name, Symbol, Number manganese, Mn, 25 Chemical series transition metals Group, Period, Block 7, 4, d Appearance silvery metallic Atomic mass 54. ... Motto: (Welsh for Wales forever) Anthem: Hen Wlad Fy Nhadau Capital Cardiff Largest city Cardiff Official language(s) Welsh, English Government Constitutional monarchy  - Queen Queen Elizabeth II  - Prime Minister of the UK Tony Blair MP  - First Minister Rhodri Morgan AM Unification    - by Gruffudd ap Llywelyn 1056  Area    - Total 20,779...

Treatment

Oversight

In the United Kingdom, many discharges from abandoned mines are exempt from regulatory control. In such cases the Environment Agency working with partners has provided some innovative solutions, including constructed wetland solutions such as on the River Pelena in the valley of the River Afan near Port Talbot. (see also the List of environmental organizations) The Environment Agency (Welsh: Asiantaeth yr Amgylchedd) of England and Wales was created by the Environment Act 1995, along with the Scottish Environment Protection Agency. ... A constructed wetland is an artificial marsh or swamp, created for human use, such as wastewater, storm water runoff or sewage treatment, as habitat to attract wildlife, or for land reclamation after mining or other disturbance. ... Afan is a river of South Wales, whose valley formed the territory of the medieval Lords of Afan. ... Arms of Port Talbot Port Talbot (Welsh: or Porth Talbot) is an industrial town in the traditional county of Glamorgan, south Wales, UK, with a population of approximately 50,000. ...

Although abandoned underground mines produce most of the ARD, some recently mined and reclaimed surface mines have produced ARD and have degraded local ground-water and surface-water resources. Acidic water produced at active mines must be neutralized to achieve pH 6-9 before discharge from a mine site to a stream is permitted.

In Canada, work to reduce the effects of ARD is concentrated under the Mine Environment Neutral Drainage (MEND) program. Total liability from acid rock drainage is estimated to be between $2 billion and $5 billion CAD [3]. Over a period of eight years, MEND claims to have reduced ARD liability by up to $400 million CAD, from an investment of $17.5 million CAD [4].

Methods

Carbonate neutralization

Generally, limestone or other calcareous strata that could neutralize acid are lacking or deficient at sites that produce acidic rock drainage. Limestone chips may be introduced into sites to create a neutralizing effect. Where limestone has been used, such as at Cwm Rheidol in mid Wales, the positive impact has been much less than anticipated because of the creation of an insoluble calcium sulfate layer on the limestone chips, blinding the material and preventing further neutralization. Limey shale overlaid by limestone. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... Goldenville Strata exposed at a quarry in Bedford, Canada. ... Limey shale overlaid by limestone. ... Motto: (Welsh for Wales forever) Anthem: Hen Wlad Fy Nhadau Capital Cardiff Largest city Cardiff Official language(s) Welsh, English Government Constitutional monarchy  - Queen Queen Elizabeth II  - Prime Minister of the UK Tony Blair MP  - First Minister Rhodri Morgan AM Unification    - by Gruffudd ap Llywelyn 1056  Area    - Total 20,779... Calcium sulfate is a common laboratory and industrial chemical. ...

Ion exchange

Cation exchange processes were investigated as a potential treatment for ARD. Not only would ion exchangers remove potentially toxic heavy metals from mine runoff, there was also the possibility of turning a profit off of the recovered metals. However, the cost of ion exchange materials compared to the relatively small returns, as well as the inability of current technology to efficiently deal with the vast amounts of mine discharge, renders this solution unrealistic at present. Ion exchange is a process in which ions are exchanged between a solution and an ion exchanger, an insoluble solid or gel. ...

Constructed wetlands

Constructed wetlands systems have shown promise as a more cost-effective treatment alternative to artificial treatment plants. A spectrum of bacteria and archaea, in consortium with wetland plants, may be used to filter out heavy metals and raise pH. Anaerobic bacteria in particular are known to be capable of reverting sulfate ions into sulfide ions. These sulfide ions can then bind with heavy metal ions, precipitating heavy metals out of solution and effectively reversing the entire process. A constructed wetland is an artificial marsh or swamp, created for human use, such as wastewater, storm water runoff or sewage treatment, as habitat to attract wildlife, or for land reclamation after mining or other disturbance. ...

Interestingly enough, T. ferrooxidans - the very bacteria which appears to be the problem - has also been shown to be effective in treating heavy metals in constructed wetland treatment systems.

The attractiveness of a constructed wetlands solution lies in its passivity - building an artificial wetlands is a relatively cheap one-time investment which continuously works to reduce acidity and heavy metal concentration. Although promising, constructed wetlands take much time to completely cleanse an area, and are simply not enough to deal with extensively polluted discharge. Constructed wetland effluent often requires additional treatment to completely stabilize pH. Also, the products of bacterial processes are unstable when exposed to oxygen, and require special disposal to ensure no further contamination. Other issues include seasonal variation in the activity of cleansing organisms, as well as the lack of a practical passive means of moving mine discharge through the most efficient regions of purification.

Active Treatment with Aeration

In some discharges, HCO3-, a base, enters into the runoff from the breakdown of organic matter in the mine, such as mine timbers, or from the groundwater interaction with limestone. The base then neutralizes the acid in the runoff, forming carbonic acid. A base in chemistry is a chemical substance which has a free pair of electrons to bind a hydrogen ion commonly referred to as a proton (IUPAC definition). ...

H⁺ + HCO₃^- = H₂CO₃. (1)

When this solution reaches the ground surface, the water is exposed to the air and the dissolved CO2 will degas into the atmosphere. This lowers the concentration of CO2, allowing more H2CO3 to decompose, which in turn allows the neutralization of more acid. Neutralization is a chemical reaction, also called a water forming reaction, in which an acid and a base or alkali (soluble base) react and produce a salt and water. ...

H₂CO₃ = H₂O + CO₂. (2)

The rise in pH promotes the oxidation of the iron and the formation of iron hydroxide, which will precipitate out of the solution, leaving little iron left in the water. Large air pumps and diffuser tubes can be used to allow more CO2 to outgas, and thus precipitate more iron out of the solution. This explained method can only work, however, for runoff which is naturally basic.

List of acid mine drainage sites worldwide

This list includes both mines producing ARD and river systems significantly affected by such drainage.

North America

• Britannia Beach, British Columbia, Canada
• Iron Mountain Mine, Shasta County, California, USA
• Clinch-Powell River system, Virginia and Tennessee, USA
• Berkeley Pit superfund site, covering the Clark Fork River and 50,000 acres (200 km²) in and around Butte, Montana, USA
• Various Coal Mines in the anthracite and bituminous coal regions of Pennsylvania, USA
• Pronto mine tailings site, Elliot Lake area, Ontario, Canada
• North Fork of Kentucky River, Kentucky, USA
• Cheat River Watershed, West Virginia, USA
• Copperas Brook Watershed, from the Elizabeth Mine in S. Strafford, Vermont, impacting the Ompompanoosuc River

To meet Wikipedias quality standards, this article or section may require cleanup. ... Shasta County is a county located in the northern portion of the U.S. state of California, in the Cascade Mountains. ... The Clinch River rises in southwestern Virginia and flows into East Tennessee. ... The Powell River in the United States rises in southwest Virginia and flows into East Tennessee. ... It has been suggested that Rest of Virginia be merged into this article or section. ... Official language(s) English Capital Nashville Largest city Memphis Largest metro area Nashville Area  Ranked 36th  - Total 42,169 sq mi (109,247 km²)  - Width 120 miles (195 km)  - Length 440 miles (710 km)  - % water 2. ... The Berkeley Pit is a gigantic former open pit copper mine located in Butte, Montana, and is the one of the largest Superfund sites. ... Checking the status of a cleanup site Superfund is the common name for the United States environmental law that is officially known as the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), 42 U.S.C. §§ 9601 to 9675, which was enacted by the United States Congress on December 11... The Clark Fork River is a river in the U.S. states of Montana and Idaho, approximately 360 mi (579 km) long. ... Uptown Butte Butte is a city that is in Silver Bow County, Montana and is the county seat. ... Anthracite coal Anthracite is a hard, compact variety of mineral coal that has a high luster. ... Asphalt is a highly viscous liquid that occurs naturally in most crude petroleums. ... Official language(s) None Capital Harrisburg Largest city Philadelphia Area  Ranked 33rd  - Total 46,055 sq mi (119,283 km²)  - Width 160 miles (255 km)  - Length 280 miles (455 km)  - % water 2. ... Elliot Lake (2001 population 11,956) is a city in Northern Ontario, Canada. ... Motto: Ut Incepit Fidelis Sic Permanet (Latin: Loyal she began, loyal she remains) Official languages None Flower White Trillium Tree Eastern White Pine Bird Common Loon Capital Toronto Largest city Toronto Lieutenant-Governor James K. Bartleman Premier Dalton McGuinty (Liberal) Parliamentary representation  - House seats  - Senate seats 106 24 Area Total... Official language(s) English Capital Charleston Largest city Charleston Area  Ranked 41st  - Total 24,244 sq mi (62,809 km²)  - Width 130 miles (210 km)  - Length 240 miles (385 km)  - % water 0. ...

Europe

• Cwm Rheidol, Wales
• Aznalcollar mine on the Agrio River, Spain

Motto: (Welsh for Wales forever) Anthem: Hen Wlad Fy Nhadau Capital Cardiff Largest city Cardiff Official language(s) Welsh, English Government Constitutional monarchy  - Queen Queen Elizabeth II  - Prime Minister of the UK Tony Blair MP  - First Minister Rhodri Morgan AM Unification    - by Gruffudd ap Llywelyn 1056  Area    - Total 20,779...

Oceania

• Buller coalfield in the north-west of the South Island, New Zealand

  Categories: Stub | Nelson, New Zealand | Territorial Authorities of New Zealand ...

South America

• Potosi, Bolivia, metal mines in and around Cerro Rico

Potosi may refer to: Potosí, a city and department in Bolivia A few places in the United States: Potosi, Missouri Potosi, Texas Potosi, Wisconsin Potosi (town), Wisconsin This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...

See also

• Mining
• Environmental Protection Agency
• Environment Agency
• Clean Water Act
• Bioleaching
• Sulfide mining

This article is about mineral extraction. ... EPA redirects here. ... (see also the List of environmental organizations) The Environment Agency (Welsh: Asiantaeth yr Amgylchedd) of England and Wales was created by the Environment Act 1995, along with the Scottish Environment Protection Agency. ... The Clean Water Act, 33 U.S.C.A. § 1251 et seq. ... Bioleaching is the extraction of specific metals from their ores through the use of bacteria. ... Sulfide mining is the mining of rocks which contain large amounts of sulfide. ...

External links

• Information source on Acid Mine Drainage from TechnoMine
• The Science of Acid Mine Drainage and Passive Treatment
• Pictures of yellow boy
• Abandoned Mine Research
• USGS Mine Drainage
• Coal-Mine-Drainage Projects in Pennsylvania
• AMRClearinghouse.org
• Environmental Mining Council of British Columbia
• World's Most Acidic Waters are Found Near Redding, California (pH -3.6)
• Overview of chemical processes involved
• Acid Mine Drainage Overview
• Assessment of treatment methods (PDF)