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Concept
Arsenic contamination of groundwater
Résumé
Arsenic contamination of groundwater is a form of groundwater pollution which is often due to naturally occurring high concentrations of arsenic in deeper levels of groundwater. It is a high-profile problem due to the use of deep tube wells for water supply in the Ganges Delta, causing serious arsenic poisoning to large numbers of people. A 2007 study found that over 137 million people in more than 70 countries are probably affected by arsenic poisoning of drinking water. The problem became a serious health concern after mass poisoning of water in Bangladesh. Arsenic contamination of ground water is found in many countries throughout the world, including the US.
The World Health Organization recommends limiting arsenic concentrations in water to 10 μg/L, although this is often an unattainable goal for many problem areas due to the difficult nature of removing arsenic from water sources.
Approximately 20 major incidents of groundwater arsenic contamination have been reported. Of these, four major incidents occurred in Asia—in Bangladesh; West Bengal, India; Inner Mongolia, China; and Taiwan. Locations of potentially hazardous wells have been mapped in China.
Gold mining can contaminate groundwater with arsenic, because the element typically occurs in gold-containing ores. Gold processing releases arsenic from mine tailings, and contaminated groundwater may be unsafe to drink for decades.
Arsenic contaminated water typically contains arsenous acid and arsenic acid or their derivatives. Their names as "acids" is a formality; these species are not aggressive acids but are merely the soluble forms of arsenic near neutral pH. These compounds are extracted from the underlying rocks that surround the aquifer. Arsenic acid tends to exist as the ions [HAsO4]2− and [H2AsO4]− in neutral water, whereas arsenous acid is not ionized.
An analysis of water and food consumption in Socaire, a rural village in Chile, found that between November 2008 and September 2009, the total intake of arsenic by the villagers correlated with the amount of water and local produce consumed.
Source officielle
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