• What is the role of arsenic in the mining industry?

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    Arsenic is a naturally occurring element commonly found as an impurity in metal ores, and is produced commercially for use in pesticides, wood preservatives, and metal alloys. Arsenic can be toxic in large doses, and the mining industry monitors and prevents its release into the environment.

    General information

    Arsenic is the 20th most abundant component of the Earth’s crust, and is widely distributed in rocks and soil, in natural waters, and in small amounts in all living things. [1] It is a metalloid, which means that it can behave as a metal or as a nonmetal. [2] Arsenic is rarely found as a pure metal, but is often a component in sulphur-containing minerals, the most common of which is arsenopyrite. [2] Commercially, arsenic is produced as arsenic trioxide or as a pure metal. [3]

    Arsenic toxicity

    Arsenic is classified in Group 1 of the Priority Substances List by Health Canada, which means that it is poisonous and causes cancer in humans. [4] Consuming a large amount of arsenic over a lifetime can increase the risk of cancer in internal organs such as the bladder, lungs, and liver. [4] Noncancerous effects of arsenic exposure in humans include skin discolouration and thickening, cardiovascular and gastrointestinal diseases, and gangrene or Blackfoot disease. [4]

    For most Canadians, the primary source of exposure to arsenic is from minor amounts in fish and meat. [4] However, in areas with naturally high levels of arsenic in the groundwater, arsenic poisoning from drinking water is a serious concern. [5] Countries with high arsenic levels in their groundwater include Bangladesh, Taiwan, Mexico, Chile, China, and India. [5] High concentrations of arsenic in lakes and streams can also be lethal to freshwater fish, invertebrates, and plant life. [6]

    Although some plants are able to grow in soil with high levels of arsenic, most do not grow as well or produce as much fruit as they would in uncontaminated soil. [7] With a few exceptions, plants do not accumulate arsenic in high concentrations, and will die in severely contaminated soil. [7]

    Natural sources of arsenic

    Arsenic is released into the environment naturally through the weathering and erosion of sulphide minerals. [1] These sulphide minerals can form soils with very high concentrations of arsenic, and can dissolve in water. [1] An estimated 25% of arsenic emissions into the atmosphere come from natural sources, mostly volcanoes. [8] The majority of the arsenic released ends up in the soil and the ocean. [8]

    Since valuable metals such as copper and gold can also be found in sulphide mineral deposits, mining exploration companies will often look for soil and water with a naturally high arsenic content as a means of locating an ore body. [9] It is therefore very important to establish baseline or existing arsenic concentrations in the surrounding environment in order to distinguish between human contamination and natural background levels. [10] The measurement of baseline concentrations is usually part of the environmental impact assessment processes practised in more than 100 countries. [11]

    Human activities which intensify the release of arsenic

    A number of human activities have the potential to increase arsenic concentrations in the air, water, and soil on a local scale. [1] The rate of arsenic release from sulphide minerals can be sped up by mining activities, which expose the minerals to weathering processes during excavation. [1] Arsenic dust is produced during copper and gold smelting, and coal combustion. [8] The direct application of arsenic in the form of pesticides or wood preservatives has historically been a major source of arsenic to soils. [1] Freshwaters and associated ecosystems may be impacted by arsenic runoff from contaminated sites, but groundwater contamination as a result of human activity is rare, as arsenic is strongly attracted to soil particles and sediments. [1] In contrast, it is the natural release of arsenic from geologic materials which has become a threat to drinking water supplies around the world. [5]

    Arsenic in the mining industry

    Atmospheric arsenic emissions from copper smelting represent the largest contribution of arsenic from the mining and metals industry by far and have been the focus of pollution control technologies and increasingly stringent regulations. [8] Arsenic can also be leached out of some metal ores by cyanide or acid rock drainage but can be captured and removed from wastewater before it is released into the environment. [12]

    How the mining industry prevents arsenic pollution

    A number of technologies are being used to capture and remove arsenic from smelting stacks and mine tailings. Air pollution can be controlled effectively using scrubbers, electrostatic precipitators, and baghouses in smelters, which are capable of removing up to 99.7% of the dust and fumes produced during roasting and smelting. [13] Mine tailings and wastewater can be treated with iron compounds, which react with the arsenic and remove it from the water. [14] Arsenic can also be filtered from waste and tailings with iron oxides, clay liners, and activated charcoal filters, which can be disposed of safely. [14] The use of plants, wetlands, and iron nanoparticles to remove arsenic from already contaminated areas is also being studied. [14, 15]

    Environmental releases of arsenic from mining activities in Canada decreased by 79% between 1993 and 2009 [16]. This is largely due to the closure of the Giant gold mine in 2000, more stringent environmental regulations, and the subsequent investment by Canada’s mining companies in pollution control technologies. [1, 17, 18]  In general, the provincial governments are responsible for controlling pollution from industrial and business activities through the use of permits and approvals. [19] Because arsenic is classified as a toxic substance in the Canadian Environmental Protection Act and the Fisheries Act, it is also regulated by the federal government. [20] From 2003-2010, the arsenic concentration in 99% of mine outflow water samples was below the acceptable limit defined by the Canadian Metal Mining Effluent Regulations. [21, 22]

    Uses of arsenic

    The reported world production of arsenic was 52,800 tonnes in 2010. [23] Demand for arsenic has been declining since the 1970s when inorganic arsenic salts were still used extensively as pesticides. [8] Globally, an estimated 50% of arsenic produced continues to be used to make arsenic-based insecticides and herbicides, and another 30% is used to make chromated copper arsenate (CCA) wood preservatives. [8] The electronics industry uses 5% of the arsenic produced to make gallium-arsenic semiconductors for use in cell phones, solar panels, and light emitting diodes (LEDs), and the remaining 15% is used in glassmaking, and to harden metal alloys in ammunition, solders, and bearings. [24]

    Because of concerns of arsenic contamination of soil surrounding treated wood, Canada and the United States entered into a voluntary agreement in 2003 to ban the use of CCA in residential applications. [24] However, CCA is still used to pressure treat wood for industrial applications such as marine timbers and utility poles. [1, 24]

    Arsenic production

    Arsenic trioxide is obtained as a byproduct from dusts and residues produced during the treatment of other metal ores such as gold and copper. [25] The arsenic trioxide can be purified on site or sold to a refinery. [7] China is the world’s leading producer of arsenic (25,000 tonnes in 2010), but Chile (11,000 tonnes), Morocco (8,000 tonnes), and Peru (4,500 tonnes) are also important producers. [23]

    Arsenic in Canada

    Arsenic is no longer produced commercially in Canada, but it has historically been a significant byproduct of gold and copper mining. [1] In 2010, 41 tonnes of arsenic were imported from the United States for use in the manufacturing of CCA and metal alloys. [24] Inorganic arsenic-based pesticides were used heavily on orchards up until the 1970s, and organic arsenic pesticides continued to be used until more recently. [1, 26] Monosodium methanearsonate (MSMA), an organic arsenic-based pesticide, was applied from 1995-2004 to pine trees in B.C. in an attempt to control the mountain pine beetle outbreak. [27] However, ecology researchers found high levels of arsenic in woodpeckers and other birds which were eating the beetles. [26] As a result of the harmful effects observed on the birds, the use of MSMA was banned in Canada in 2005. [27]


    Case Study: Giant Mine in Yellowknife, Northwest Territories

    When it was in operation from 1948-1999, Giant Mine in Yellowknife, NWT, produced an estimated 7.6 million ounces of gold. [28] The gold at Giant Mine was found within arsenopyrite sulphide deposits which also contained large amounts of arsenic. [28]

    The gold was released from the ore by roasting it at high temperatures, which gave off an arsenic-rich gas. [29] Initially, the arsenic was released directly into the environment, but in 1951 a Cold Cotrell Electrostatic Precipitator was installed which removed much of the arsenic trioxide dust from the air. [28] A Dracco Baghouse was added in 1958 to further control the arsenic emissions. [28]

    Over the lifetime of the mine 237,000 tonnes of arsenic trioxide dust were removed from the pollution stream and stored in sealed chambers underground in the mine. [29] This was considered to be an acceptable long term storage solution because the mine was isolated by permafrost which was expected to reseal once the mining activities had ceased. [29] However, further mining activity in the area caused the permafrost to melt, which has allowed water to get in and out of the arsenic dust chambers and contaminate the surrounding area with dissolved arsenic. [28]

    The Giant mine was officially abandoned in 2005, and now falls under the responsibility of Aboriginal Affairs and Northern Development Canada (AANDC). [28] The Government of Canada and the Government of the Northwest Territories are sharing the cost of the remediation of the mine according to a 10-year Cooperation Agreement signed in 2005. [30] All the water seeping into the mine is being collected and pumped to a treatment plant on the surface, and the site is undergoing remediation. [29] The proposed remediation of Giant Mine involves freezing the ground around the arsenic dust chambers using thermosyphons (self-sustaining heat pumps), and is currently being tested in a Freeze Optimization Study. [29] More information on the Giant Mine remediation project can be found on the AANDC website.

    Show References


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    2Mining Information Institute. Mineral Photos - Arsenic. Mineral Photos 2012 [cited 2012 May 18]; Available from: http://www.mii.org/Minerals/photoarsenic.html.

    3GreenFacts. Scientific Facts on Arsenic. Publications 2012 [cited 2012 May 18]; Available from: http://www.greenfacts.org/en/arsenic/index.htm.

    4Canada, Health Canada. Guidelines for Canadian drinking water quality: Guideline technical document -- Arsenic, 2006; Available from: http://www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/arsenic/index-eng.php.

    5International Groundwater Resources Assessment Centre. Arsenic in Groundwater: A World Problem, 2009 [cited 2012 May 25]; Available from: http://www.un-igrac.org/publications/301.

    6Canadian Council of Ministers of the Environment, Canadian Water Quality Guidelines for the Protections of Aquatic Life: Arsenic, 2001, Canadian Council of Ministers of the Environment: Winnipeg.

    7Canadian Council of Ministers of the Environment, Canadian Soil Quality Guidelines for the Protection of Environmental and Human Health: Arsenic (Inorganic)(1997), 2001, Canadian Council of Ministers of the Environment: Winnipeg.

    8Matschullat, J. Arsenic in the Geosphere -- A Review. The Science of the Total Environment, 2000 [cited 249; 16]. Available from: http://jbouzan.com/files/class/chem360/ArsenicInTheGeosphere-AReview.pdf.

    9Canada, Health Canada. Appendix A: Screening Contaminants of Potential Concern for Local or Regional Background (Natural) Soil, Groundwater and Surface Water Concentrations. Federal Contaminated Site Risk Assessment in Canada Part I: Guidance on Human Health Preliminary Quantitative Risk Assessment (PQRA), 2007 [cited 2012 June 1]; Available from: http://hc-sc.gc.ca/ewh-semt/pubs/contamsite/part-partie_i/appendix-a-annexe-eng.php.

    10Castro de Esparza, M. L. The presence of arsenic in drinking water in Latin America and its effect on public health, 2006 [cited 2012 May 29]; Available from: http://www.bvsde.paho.org/bvsacd/cd51/arsenic-presence.pdf.

    11Noble, B.F., Introduction to Environmental Impact Assessment: A Guide to Principles and Practice, 2006, Don Mills, Ontario: Oxford University Press.

    12Williams, M., Arsenic in Mine Waters: An International Study. Environmental Geology, 2001. 40(3): p. 12.

    13Vallero, D.A., Fundamentals of Air Pollution, 2007, Amsterdam: Elsevier.

    14Straskraba, V. and R.E. Moran, Environmental Occurrence and Impacts of Arsenic at Gold Mining Sites in the Western United States. International Journal of Mine Water, 1990. 9(1-4): p. 11.

    15Rice University Press Release. First 'nanorust' field test slated in Mexico, 2009 [cited 2012 May 31]; Available from: http://www.understandingnano.com/nanoparticle-water-pollution-iron-oxide-arsenic.html.

    16The Mining Association of Canada, F&F 2011: FACT$ & FIGURE$ OF THE CANADIAN MINING INDUSTRY, 2011.

    17Canada, Minerals and Metals Division, National Office of Pollution Prevention, Environment Canada. Multi-pollutant Emission Reduction Analysis Foundation (MERAF) for the Base Metals Smelting Sector, 2002 [cited 2012 June 6]; Available from: http://www.ccme.ca/assets/pdf/bms_summary_meraf_e.pdf.

    18Xstrata Copper Canada. Xstrata Copper News Release: Horne Smelter Announces Significant Investment, 2006 [cited 2012 May 29]; Available from: http://www.xstrata.com/media/news/2006/09/21/0700CET/.

    19British Columbia, Government of British Columbia. BC Air Quality: Levels of Government Involved, 2012 [cited 2012 June 6]; Available from: http://www.bcairquality.ca/regulatory/levels-of-government.html.

    20Canada, Environment Canada. Canadian Environmental Protection Act, 1999 (CEPA 1999), 2012 [cited 2012 June 6]; Available from: http://www.ec.gc.ca/lcpe-cepa/default.asp?lang=En&n=26A03BFA-1.

    21Canada, Natural Resources Canada. Mining Sector Performance Report 1998-2008, 2010 [cited 2012 May 31]; Available from: http://www.nrcan.gc.ca/minerals-metals/publications-reports/3398#es.

    22Canada, Environment Canada. Summary Review of Performance of Metal Mines Subject to the Metal Mining Effluent Regulations, 2012 [cited 2012 May 25, 2012]; Available from: http://www.ec.gc.ca/pollution/default.asp?lang=En&n=C6A98427-1.

    23Brooks, W.E., 2010 Minerals Yearbook: Arsenic [Advance Release]. Minerals Yearbook 2011 [cited 2012 May 25]; Available from: http://minerals.usgs.gov/minerals/pubs/commodity/arsenic/myb1-2010-arsen.pdf.

    24Carex Canada. Arsenic. Profiles and Estimates, 2012 [cited 2012 May 24]; Available from: http://www.carexcanada.ca/en/arsenic/.

    25US National Toxicology Program. Arsenic, 2011 [cited 2012 May 22]; Available from: http://ntp.niehs.nih.gov/ntp/ohat/diabetesobesity/Wkshp/ArsenicGroupReviewV3formatted.pdf.

    26Canada, Environment Canada. A Case Against Arsenic-Based Pesticides. 2008 [cited 2012 May 24]; Available from: http://www.ec.gc.ca/envirozine/default.asp?lang=en&n=B9657723-1.

    27Price, C. Mountain Pine Bettle Controls: Reducing Unintended Harm to Forest Birds, 2012 [cited 2012 May 24]; Available from: http://www.ec.gc.ca/scitech/default.asp?lang=En&n=4B40916E-1&xsl=privateArticles2,viewfull&po=DA247312.

    28Canada, Aboriginal Affairs and Northern Development Canada. History of Giant Mine, 2010 [cited 2012 May 16]; Available from: http://www.aadnc-aandc.gc.ca/eng/1100100027388.

    29Canada, Aboriginal Affairs and Northern Development Canada. Arsenic Trioxide at Giant Mine,, 2010 [cited 2012 May 16]; Available from: http://www.aadnc-aandc.gc.ca/eng/1100100027422/1100100027423.

    30Canada, Aboriginal Affairs and Northern Development Canada. Archived -- Backgrounder -- Cooperation Agreement regarding the Giant Mine Remediation Project, 2012 [cited 2012 June 5]; Available from: http://www.aadnc-aandc.gc.ca/aiarch/mr/nr/j-a2005/02597bk-eng.asp.

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