Wright, Bristol, UK, pp — J Appl Microbiol — Greer J The price of gold: environmental costs of the new gold rush. Ecologist 23 3 — Ciba Foundation Symposium Wiley, Chichester, pp 49— Hallock RJ Elimination of migratory bird mortality at gold and silver mines using cyanide extraction.
Nevada Mining Association, Reno. Ecotoxicology — Iowa State University Press, Ames, pp 99— Guinn, Hoboken. Freshwater Salmon Res Ser Homan ER Reactions, processes and materials with potential for cyanide exposure. Wright, Bristol, UK, pp 1— Biochem J — Keilin D Cytochrome and respiratory enzymes. Proc Soc Lond Biol Sci — Kempton H Dealing with the legacy of mine pit lakes. Southwest Hydrol 1 3 : 24— Koenig R Wildlife deaths are a grim wake-up call in eastern Europe. Science — Korte F, Coulston F Some considerations on the impact of ecological chemical principles in practice with emphasis on gold mining and cyanide.
Ecotoxicol Environ Saf — Korte F, Spiteller M, Coulston F The cyanide leaching gold recovery process is a nonsustainable technology with unacceptable impacts on ecosystems and humans: the disaster in Romania. Kovac C Cyanide spill could have long term impact. Br Med J Can J Fish Aquat Sci — Kovacs TG, Leduc G b Acute toxicity of cyanide to rainbow trout acclimated at different temperatures.
Kuipers JR Water treatment as a mitigation method for pit lakes. Southwest Hydrol 1 3 : 18— Leduc G Deleterious effects of cyanide on early life stages of Atlantic salmon Salmo salar. J Fish Res Board Can — Leduc G Ecotoxicology of cyanides in freshwater. Academic Press, New York, pp — Leduc G Cyanides in water: toxicological significance. Raven Press, New York, pp — Publ NRCC Natural Resources Council of Canada, Ottawa. Folia Microbiol — Pertanika — Ma J, Pritsos CA Tissue-specific bioenergetic effects and increased enzymatic activities following acute sublethal peroral exposure to cyanide in the mallard duck.
Toxicol Appl Pharmacol — Water Resour Invest Rep Geological Survey, Boulder, CO. Arch Environ Contam Toxicol — Miller GC Precious metals pit lakes: controls on eventual water quality.
Moore JW Influence of water movements and other factors on distribution and transport of heavy metals in a shallow bay Canada. Moreno J, Sinton P Modeling mine pit lakes. Southwest Hydrol 1 3 —21, Cyanide is a rapidly acting, potentially deadly chemical. How is cyanide used in mining? There are two types of leaching: Heap leaching : In the open, cyanide solution is sprayed over huge heaps of crushed ore spread atop giant collection pads.
Vat or tank leaching : The ore is mixed with cyanide solution in large tanks. Although the chances of spills are lower because the leaching process is more controlled, the resulting waste, known as tailings, is stored behind large dams tailings impoundments which can and do fail catastrophically. Cyanide's efficiency makes mining more wasteful Because cyanide leaching is very efficient, it allows profitable mining of much lower ore grades.
Partially due to cyanide, modern mines are much larger than before cyanide was used; create vast open pits; and produce huge quantities of waste.
What are the dangers of using cyanide? For example: Mexico, , gallons of cyanide solution spilled from a retaining pond at the Proyecto Magistral mine, after heavy rains. Kyrgyzstan, Kumtor Gold Mine , A truck carrying 2 tons of sodium cyanide crashed into the Barskoon river, resulting in more than 2, people seeking medical care. Romania, Aural Gold , : A tailings dam ruptured, spilling 3.
United States, Zortman-Landusky Mine, Montana , : 52, gallons of cyanide solution poisoned the aquifer that supplies fresh drinking water for the town of Zortman.
Both the use and disposal of cyanide present significant safety and environmental risks. Cyanide and cyanide gas are both extremely toxic and great care has to be taken during ore processing to avoid exposure for workers. Solutions containing cyanide have to be carefully managed to prevent the formation of cyanide gas. In addition, there are significant problems with the disposal of cyanide-containing waste.
Pure cyanide in open air breaks down into other compounds relatively quickly, however the exact composition and toxicity of these products is not well understood. One of the common breakdown products is nitrate , which itself can cause both environmental and human health problems.
Lastly, cyanide can form complexes with certain metals, such as cobalt , and these can persists for many years in groundwater. Many old mines, and some current mines, simply place cyanide waste into the mine tailings ponds along with other mining waste. Failure of a tailings dam containing cyanide can be a massive environmental problem, resulting in the sterilization of large areas downstream. In , a tailings dam failure in Romania dumped an estimated tons of cyanide into a river system, contaminating drinking water and killing fish up to miles downstream, with effects purportedly lasting for years.
In comparison to acid mine drainage , cyanide has a higher toxicity, but is shorter lived. Acid mine drainage can last for thousands of years, whereas cyanide will break down within a few years at most. However, its high toxicity means that even a relatively small spill can have major consequences. Many modern mines now use a "de-toxification" process that converts cyanide into the less toxic cyanate before combining it with the mine tailings waste. In addition, the majority of cyanide gold mines use "impermeable" liners in their tailings ponds and underneath their heap leaching operations.
However, leaks and tears in these liners have been a continual problem at many mines.
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