Extractive industry

Extractive industries, and the processes of refining their raw products, are major sources of waste into the marine environment. The oil and gas industry is well known in this regard . Other forms of mineral extraction can be equally problematic, from the deliberate use of the ocean as a dumping ground for mine tailings to the accidental spillage of toxic compounds.
In some cases mine-tailings are largely, or entirely, non-toxic, in which case their impact on the natural environment is simply one of physical smothering. A long-term study of a copper-mine in Vancouver Island (Canada) which released 50,000 tonnes of silt every day for 25 years into a naturally sediment filled inlet showed a clear loss in biodiversity at high deposition rates (about 20cm per year or greater). However a clear succession was observed back to expected levels of biodiversity as deposition ceased.
Certain mineral extraction processes involve the use of toxic chemicals, such as mercury or sodium cyanide in the extraction of gold from particular ores. The release of these toxins into the environment has been particularly problematic in some areas by very small-scale operations operated by individuals. It has been estimated that 100 tonnes of mercury are released into the Amazon area each year as a result of very small-scale, often illegal gold extraction. Industrial extraction also creates problems, especially in areas where there are few legal measures or efforts to police pollution. Several major multinational mining companies have been responsible for major pollution events into rivers and coastal waters resulting from the deliberate release of suspended sediments, or the accidental failure of tailings dams, resulting in massive pulses of pollutant release.

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