Difference between revisions of "Arsenic"

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Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250. Arsenic is a metalloid. It can exist in various allotropes, although only the grey form has important use in industry.
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'''Arsenic contamination of groundwater''' is a natural occurring high concentration of [[arsenic]] in deeper levels of groundwater. It is a high-profile problem due to the use of deep tubewells 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.
  
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The main use of metallic arsenic is for strengthening alloys of copper and especially lead (for example, in car batteries). Arsenic is a common n-type dopant in semiconductor electronic devices, and the optoelectronic compound gallium arsenide is the most common semiconductor in use after doped silicon. Arsenic and its compounds, especially the trioxide, are used in the production of pesticides (treated wood products), herbicides, and insecticides. These applications are declining, however.
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==Health effects of arsenic==
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Consuming water contaminated by arsenic can cause skin cancer, and bladder as well as cardiovascular disease.
  
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Arsenic is notoriously poisonous to multicellular life, although a few species of bacteria are able to use arsenic compounds as respiratory metabolites. Arsenic contamination of groundwater is a problem that affects millions of people across the world.
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Some research concludes that even at the lower concentrations, arsenic contamination is a major causes of death.  A study conducted in a contiguous six-county area of southeastern Michigan investigated the relationship between moderate arsenic levels and 23 selected disease outcomes. Disease outcomes included several types of cancer, diseases of the circulatory and respiratory system, diabetes mellitus, and kidney and liver diseases. Elevated mortality rates were observed for all diseases of the circulatory system.  The researchers acknowledged a need to replicate their findings.<ref>, Jaymie R. Meliker, [http://www.ehjournal.net/content/6/1/4 ''Arsenic in drinking water and cerebrovascular disease, diabetes mellitus, and kidney disease in Michigan: a standardized mortality ratio analysis''] Environmental Health Magazine. Volume 2:4. 2007. Accessed 9 Sept. 2008.</ref>
  
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==Characteristics==
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A preliminary study shows a relationship between arsenic exposure measured in urine and Type II diabetes. The results supported the hypothesis that low levels of exposure to inorganic arsenic in drinking water may play a role in diabetes prevalence.<ref>Ana Navas-Acien, "Arsenic Exposure and Prevalence of Type 2 Diabetes in US Adults," ''Journal of American Medical Association'', v.300, n.7 (August 2008).</ref>
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====Physical Characteristics====
 
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The three most common allotropes are metallic grey, yellow and black arsenic, with grey being the most common. Grey arsenic (α-As, space group R3m No. 166) adopts a double-layered structure consisting of many interlocked ruffled six-membered rings. Because of weak bonding between the layers, grey arsenic is brittle and has a relatively low Mohs hardness of 3.5. Nearest and next-nearest neighbors form a distorted octahedral complex, with the three atoms in the same double-layer being slightly closer than the three atoms in the next. This relatively close packing leads to a high density of 5.73 g/cm3. Grey arsenic is a semimetal, but becomes a semiconductor with a bandgap of 1.2–1.4 eV if amorphized. Yellow arsenic is soft and waxy, and somewhat similar to tetraphosphorus (P4). Both have four atoms arranged in a tetrahedral structure in which each atom is bound to each of the other three atoms by a single bond. This unstable allotrope, being molecular, is the most volatile, least dense and most toxic. Solid yellow arsenic is produced by rapid cooling of arsenic vapour, As4. It is rapidly transformed into the grey arsenic by light. The yellow form has a density of 1.97 g/cm3. Black arsenic is similar in structure to red phosphorus.
 
  
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====Isotopes====
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Arsenic in drinking water may also compromise immune function {{cite web |url=http://www.eurekalert.org/pub_releases/2009-05/mbl-sli052009.php |title=Scientists link influenza A (H1N1) susceptibility to common levels of arsenic exposure |format= |work= |accessdate=}}.
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Naturally occurring arsenic is composed of one stable isotope, 75As. As of 2003, at least 33 radioisotopes have also been synthesized, ranging in atomic mass from 60 to 92. The most stable of these is 73As with a half-life of 80.3 days. Isotopes that are lighter than the stable 75As tend to decay by β+ decay, and those that are heavier tend to decay by β- decay, with some exceptions.
 
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At least 10 nuclear isomers have been described, ranging in atomic mass from 66 to 84. The most stable of arsenic's isomers is 68mAs with a half-life of 111 seconds.
 
  
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====Chemistry====
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== Contamination in Bangladesh and West Bengal, India ==
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When heated in air, arsenic oxidizes to arsenic trioxide; the fumes from this reaction have an odour resembling garlic. This odour can be detected on striking arsenide minerals such as arsenopyrite with a hammer. Arsenic (and some arsenic compounds) sublimes upon heating at atmospheric pressure, converting directly to a gaseous form without an intervening liquid state at 887 K (614 °C). The triple point is 3.63 MPa and 1,090 K (820 °C). Arsenic makes arsenic acid with concentrated nitric acid, arsenious acid with dilute nitric acid, and arsenic trioxide with concentrated sulfuric acid.
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Arsenic contamination of the groundwater in Bangladesh is a serious problem. Prior to the 1970s, Bangladesh had one of the highest infant mortality rates in the world. Ineffective water purification and sewage systems as well as periodic monsoons and flooding exacerbated these problems. As a solution, UNICEF and the World Bank advocated the use of wells to tap into deeper groundwater. Millions of wells were constructed as a result. Because of this action, infant mortality and diarrheal illness were reduced by fifty percent. However, with over 8 million wells constructed, approximately one in five of these wells is now contaminated with arsenic above the government's drinking water standard.
  
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==Compounds==
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In the Ganges Delta, the affected wells are typically more than 20 m and less than 100 m deep. Groundwater closer to the surface typically has spent a shorter time in the ground, therefore likely absorbing a lower concentration of arsenic; water deeper than 100 m is exposed to much older sediments which have already been depleted of arsenic.<ref>{{cite journal
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Arsenic compounds resemble in some respects those of phosphorus, which occupies the same group (column) of the periodic table. Arsenic is less commonly observed in the pentavalent state, however. The most common oxidation states for arsenic are: −3 in the arsenides, such as alloy-like intermetallic compounds; and +3 in the arsenites, arsenates(III), and most organoarsenic compounds. Arsenic also bonds readily to itself as seen in the square As3−
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| title =  Chemistry of arsenic in groundwater of Ganges-Brahmaputra river basin
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4 ions in the mineral skutterudite. In the +3 oxidation state, arsenic is typically pyramidal, owing to the influence of the lone pair of electrons.
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| author = Singh A. K.
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| journal =  [[Current Science]]
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| year = 2006
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| volume = 91
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| issue = 5
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| pages = 599&ndash;606
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| url = http://www.ias.ac.in/currsci/sep102006/599.pdf
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}}</ref>
  
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====Inorganic====
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The crisis came to international attention in 1995.<ref>David Bradley, "Drinking the water of death", ''The Guardian'', 5 January 1995</ref><ref>{{cite journal
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Arsenic forms colorless, odorless, crystalline oxides As2O3 ("white arsenic") and As2O5, which are hygroscopic and readily soluble in water to form acidic solutions. Arsenic(V) acid is a weak acid. Its salts are called arsenates, which is the basis of arsenic contamination of groundwater, a problem that affects many people. Man-made arsenates include Paris Green (copper(II) acetoarsenite), calcium arsenate, and lead hydrogen arsenate. The latter three have been used as agricultural insecticides and poisons.
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| title =  Arsenic in ground water in six districts of West Bengal, India: the biggest arsenic calamity in the world. Part I. Arsenic species in drinking water and urine of the affected people
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The protonation steps between the arsenate and arsenic acid are similar to those between phosphate and phosphoric acid. Unlike phosphorus acid, arsenous acid is genuinely tribasic, with the formula As(OH)3.
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| author = Amit Chatterjee, Dipankar Das, Badal K. Mandal, Tarit Roy Chowdhury, Gautam Samanta and Dipankar Chakraborti
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A broad variety of sulfur compounds of arsenic are known. Orpiment (As2S3) and realgar (As4S4) are somewhat abundant and were formerly used as painting pigments. In As4S10, arsenic has a formal oxidation state of +2 in As4S4, which features As-As bonds so that the total covalency of As is still in fact three.
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| journal =  Analyst
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The trifluoride, trichloride, tribromide, and triiodide of arsenic(III) are well known, whereas only Arsenic pentafluoride (AsF5) is the only important pentahalide. Again reflecting the lower stability of the 5+ oxidation state, the pentachloride is stable only below −50 °C.
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| year = 1995
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| volume = 120
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| issue =
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3| pages = 643&ndash;651
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| doi = 10.1039/AN9952000643
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}}</ref><ref>{{cite journal
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| title =  Arsenic in ground water in six districts of West Bengal, India: the biggest arsenic calamity in the world. Part 2. Arsenic concentration in drinking water, hair, nails, urine, skin-scale and liver tissue (biopsy) of the affected people
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| author = Dipankar Das, Amit Chatterjee, Badal K. Mandal, Gautam Samanta, Dipankar Chakraborti and Bhabatosh Chanda
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| journal =  Analyst
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| year = 1995
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| volume = 120
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| issue =
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3| pages = 917&ndash;925
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| doi = 10.1039/AN9952000917
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| pmid=7741255
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}}</ref> The study conducted in Bangladesh involved the analysis of thousands of water samples as well as hair, nail, and urine samples. They found 900 villages with arsenic above the government limit.
  
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====Organoarsenic compounds====
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Criticism has been leveled at the aid agencies, who denied the problem during the 1990s while millions of tube wells were sunk. The aid agencies later hired foreign experts who recommended treatment plants that were inappropriate to the conditions, were regularly breaking down, or were not removing the arsenic.<ref>[[New Scientist]], [http://www.newscientist.com/article/mg19025450.600.html Interview: Drinking at the west's toxic well] 31 May 2006.</ref>
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A large variety of organoarsenic compounds are known. Several were developed as chemical warfare agents during World War I, including vesicants such as lewisite and vomiting agents such as adamsite. Cacodylic acid, which is of historic and practical interest, arises from the methylation of arsenic trioxide, a reaction that has no analogy in phosphorus chemistry.
 
  
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====Alloys====
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In West Bengal, India, water is mostly supplied from rivers. Groundwater comes from deep tubewells, which are few in number. Because of the low quantity of deep tubewells, the risk of arsenic patients in West Bengal is comparatively less.<ref name=timesofindia>[[The Times of India]], [http://timesofindia.indiatimes.com/articleshow/864169.cms 'Use surface water. Stop digging'], interview, 26 Sep, 2004.</ref> According to the World Health Organisation, “In Bangladesh, West Bengal (India), and some other areas most drinking-water used to be collected from open dug wells and ponds with little or no arsenic, but with contaminated water transmitting diseases such as diarrhoea, dysentery, typhoid, cholera, and hepatitis. Programmes to provide ‘safe’ drinking-water over the past 30 years have helped to control these diseases, but in some areas they have had the unexpected side-effect of exposing the population to another health problem—arsenic.”<ref name=who>[[World Health Organization]], [http://www.who.int/mediacentre/factsheets/fs210/en/index.html Arsenic in Drinking Water], accessed 5 Feb 2007.</ref>
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Arsenic is used as the group 5 element in the III-V semiconductors gallium arsenide, indium arsenide, and aluminium arsenide. The valence electron count of GaAs is the same as a pair of Si atoms, but the band structure is completely different, which results distinct bulk properties. Other arsenic alloys include the II-IV semiconductor cadmium arsenide.
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The acceptable level as defined by WHO for maximum concentrations of arsenic in safe drinking water is 0.01&nbsp;mg/L. The Bangladesh government's standard is at a slightly higher rate, at 0.05&nbsp;mg/L being considered safe. WHO has defined the areas under threat: Seven of the nineteen districts of West Bengal have been reported to have ground water arsenic concentrations above 0.05&nbsp;mg/L.  The total population in these seven districts is over 34 million while the number using arsenic-rich water is more than 1 million (above 0.05&nbsp;mg/L). That number increases to 1.3 million when the concentration is above 0.01&nbsp;mg/L. According to a British Geological Survey study in 1998 on shallow tube-wells in 61 of the 64 districts in Bangladesh, 46 percent of the samples were above 0.01&nbsp;mg/L and 27 percent were above 0.050&nbsp;mg/L. When combined with the estimated 1999 population, it was estimated that the number of people exposed to arsenic concentrations above 0.05&nbsp;mg/L is 28-35 million and the number of those exposed to more than 0.01&nbsp;mg/L is 46-57 million (BGS, 2000).<ref name=who/>
  
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==Occurrence and production==
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Throughout Bangladesh, as tube wells get tested for concentrations of arsenic, ones which are found to have arsenic concentrations over the amount considered safe are painted red to warn residents that the water is not safe to drink.  
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Minerals with the formula MAsS and MAs2 (M = Fe, Ni, Co) are the dominant commercial sources of arsenic, together with realgar (an arsenic sulfide mineral) and native arsenic. An illustrative mineral is arsenopyrite (FeAsS), which is structurally related to iron pyrite. Many minor As-containing minerals are known. Arsenic also occurs in various organic forms in the environment. Inorganic arsenic and its compounds, upon entering the food chain, are progressively metabolized to a less toxic form of arsenic through a process of methylation.[18]
 
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Other naturally occurring pathways of exposure include volcanic ash, weathering of arsenic-containing minerals and ores, and dissolved in groundwater. It is also found in food, water, soil, and air.[19] The most common pathway of exposure for humans is ingestion, and the predominant source of arsenic in our diet is through seafood. An additional route of exposure is through inhalation.
 
  
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Arsenic output in 2006[21]
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One solution is “By using surface water and instituting effective withdrawal regulation. West Bengal and Bangladesh are flooded with surface water. We should first regulate proper watershed management. Treat and use available surface water, rain-water, and others. The way we're doing [it] at present is not advisable."<ref name=timesofindia/>
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In 2005, China was the top producer of white arsenic with almost 50% world share, followed by Chile, Peru, and Morocco, according to the British Geological Survey and the United States Geological Survey.[21] Most operations in the US and Europe have closed for environmental reasons. The arsenic is recovered mainly as a side product from the purification of copper. Arsenic is part of the smelter dust from copper, gold, and lead smelters.[22]
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On roasting in air of arsenopyrite, arsenic sublimes as arsenic(III) oxide leaving iron oxides,[17] while roasting without air results in the production of metallic arsenic. Further purification from sulfur and other chalcogens is achieved by sublimation in vacuum or in a hydrogen atmosphere or by distillation from molten lead-arsenic mixture.[23]
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==Water purification solutions==
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===Small-scale water treatment===
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A review of methods to remove arsenic from groundwater in Pakistan summarizes the most technically viable inexpensive methods.<ref>Fatima Hashmi and Joshua M. Pearce, “Viability of Small-Scale Arsenic-Contaminated Water Purification Technologies for Sustainable Development in Pakistan”, Sustainable Development, 19(4), pp. 223-234, 2011. [http://www3.interscience.wiley.com/journal/122394419/abstract?CRETRY=1&SRETRY=0 pdf]  [http://hdl.handle.net/1974/6828 Open access full text]</ref>
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A simpler and less expensive form of arsenic removal is known as the Sono arsenic filter, using three pitchers containing cast iron turnings and sand in the first pitcher and wood activated carbon and sand in the second.<ref>{{PDFlink|[http://www.unu.edu/env/Arsenic/Munir.pdf Evaluation of Performance of Sono 3-Kolshi Filter for Arsenic Removal from Groundwater Using Zero Valent Iron Through Laboratory and Field Studies]|272&nbsp;[[Kibibyte|KiB]]<!-- application/pdf, 279183 bytes -->}}</ref> Plastic buckets can also be used as filter containers.<ref>{{PDFlink|[http://phys4.harvard.edu/~wilson/arsenic/remediation/SONO/As%20filtration%20pictures.pdf SONO ARSENIC FILTER FROM BANGLADESH - 1]|102&nbsp;KiB<!-- application/pdf, 105080 bytes -->}} - pictures with descriptions.</ref> It is claimed that thousands of these systems are in use and can last for years while avoiding the toxic waste disposal problem inherent to conventional arsenic removal plants.  Although novel, this filter has not been certified by any sanitary standards such as NSF, ANSI, WQA and does not avoid toxic waste disposal similar to any other iron removal process.
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In the United States small "under the sink" units have been used to remove arsenic from drinking water.  This option is called "point of use" treatment.  The most common types of domestic treatment use the technologies of adsorption (using media such as Bayoxide E33, GFH, or titanium dioxide) or reverse osmosis. Ion exchange and activated alumina have been considered but not commonly used.
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===Large-scale water treatment===
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In some places, such as the United States, all the water supplied to residences by utilities must meet primary (health-based) drinking water standards.  Regulations may necessitate large-scale treatment systems to remove arsenic from the water supply. The effectiveness of any method depends on the chemical makeup of a particular water supply.  The aqueous chemistry of arsenic is complex, and may affect the removal rate that can be achieved by a particular process.
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Some large utilities with multiple water supply wells could shut down those wells with high arsenic concentrations, and produce only from wells or surface water sources that meet the arsenic standard.  Other utilities, however, especially small utilities with only a few wells, may have no available water supply that meets the arsenic standard.
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'''Coagulation/filtration''' (also known as flocculation#Water_treatment|flocculation) removes arsenic by coprecipitation and adsorption using iron coagulants. Coagulation/filtration using alum is already used by some utilities to remove suspended solids and may be adjusted to remove arsenic. But the problem of this type of filtration system is that it gets clogged very easily, mostly within two to three months. The toxic arsenic sludge are disposed of by concrete stabilization, but there is no guarantee that they won't leach out in future.
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'''Iron oxide adsorption''' filters the water through a granular medium containing ferric oxide.  Ferric oxide has a high affinity for adsorbing dissolved metals such as arsenic.  The iron oxide medium eventually becomes saturated, and must be replaced. The sludge disposal is a problem here too.
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'''Activated alumina''' is an adsorbent that effectively removes arsenic.  Activated alumina columns connected to shallow tube wells in India and Bangladesh have successfully removed both As(III) and As(V) from groundwater for decades.  Long-term column performance has been possible through the efforts of community-elected water committees that collect a local water tax for funding operations and maintenance.<ref>{{cite journal|last=SARKAR|first=S|coauthors=GUPTA, A, BISWAS, R, DEB, A, GREENLEAF, J, SENGUPTA, A|title=Well-head arsenic removal units in remote villages of Indian subcontinent: Field results and performance evaluation|journal=Water Research|date=1 May 2005|volume=39|issue=10|pages=2196–2206|doi=10.1016/j.watres.2005.04.002}}</ref>  It has also been used to remove undesirably high concentrations of fluoride.
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'''Ion Exchange''' has long been used as a water-softening process, although usually on a single-home basis.  Traditional anion exchange is effective in removing As(V), but not As (III), or arsenic trioxide, which doesn't have a net charge.  Effective long-term ion exchange removal of arsenic requires a trained operator to maintain the column.
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Both '''Reverse osmosis''' and '''electrodialysis''' (also called ''electrodialysis reversal'') can remove arsenic with a net ionic charge.  (Note that arsenic oxide, As<sub>2</sub>O<sub>3</sub>, is a common form of arsenic in groundwater that is soluble, but has no net charge.)  Some utilities presently use one of these methods to reduce total dissolved solids and therefore improve taste.  A problem with both methods is the production of high-salinity waste water, called brine, or concentrate, which then must be disposed of.
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'''Subterranean Arsenic Removal (SAR) Technology''' [http://www.insituarsenic.org SAR Technology]
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In subterranean arsenic removal (SAR), aerated groundwater is recharged back into the aquifer to create an oxidation zone which can trap iron and arsenic on the soil particles through adsorption process. The oxidation zone created by aerated water boosts the activity of the arsenic-oxidizing microorganisms which can oxidize arsenic from +3 to +5 state [http://www.insituarsenic.org SAR Technology]. No chemicals are used and almost no sludge is produced during operational stage since iron and arsenic compounds are rendered inactive in the aquifer itself. Thus toxic waste disposal and the risk of its future mobilization is prevented. Also, it has very long operational life, similar to the long lasting tube wells drawing water from the shallow aquifers.
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Six such SAR plants, funded by the World Bank and constructed by Ramakrishna Vivekananda Mission, Barrackpore & Queen's University Belfast, UK are operating in West Bengal. Each plant has been delivering more than 3,000 litres of arsenic and iron-free water daily to the rural community. The first community water treatment plant based on SAR technology was set up at Kashimpore near Kolkata in 2004 by a team of European and Indian engineers led by Dr. Bhaskar Sen Gupta of Queen's University Belfast for TiPOT.<ref>[http://www.worstpolluted.org/ 12 Cases of Cleanup & Success]</ref><ref>[http://www.worstpolluted.org/projects_reports/display/76 "World's Worst Polluted Places Report 2009"]</ref><ref>[http://www.scientificamerican.com/podcast/episode.cfm?id=can-the-worlds-most-polluted-places-09-10-29&SID=mail&sc=emailfriend Scientific American]</ref><ref>[http://uk.reuters.com/article/idUKTRE59R4BE20091028?pageNumber=1&virtualBrandChannel=0 Reuters Global]</ref>
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SAR technology had been awarded Dhirubhai Ambani Award, 2010 from IChemE UK for Chemical Innovation. Again, SAR was the winner of the [http://www.thestandrewsprize.com/lists/2010.htm St. Andrews Award for Environment, 2010]. The SAR Project was selected by the Blacksmith Institute - New York & Green Cross- Switzerland as one of the "12 Cases of Cleanup & Success" in the World's Worst Polluted Places Report 2009. (Refer: [http://www.worstpolluted.org/files/FileUpload/files/2009-report/Blacksmith-Institute-Green-Cross-Switzerland-WWPP-Report-2009.pdf www.worstpolluted.org]).
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Currently, large scale SAR plants are being installed in USA, Malaysia, Cambodia, and Vietnam.
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==Dietary intake==
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Researchers from Bangladesh and the United Kingdom have recently claimed that dietary intake of arsenic adds a significant amount to total intake where contaminated water is used for irrigation.<ref>{{cite news | url = http://www.scidev.net/News/index.cfm?fuseaction=readNews&itemid=2975&language=1 | author = Mustak Hossain | title = Toxic rice harvested in southwestern Bangladesh | publisher = SciDev.Net | date =  2006-07-13}}</ref><ref>{{cite journal | title = Increase in Rice Grain Arsenic for Regions of Bangladesh Irrigating Paddies with Elevated Arsenic in Groundwaters | journal = [[Environ. Sci. Technol]] | volume = 40 | issue = 16 | pages = 4903–4908 |doi = 10.1021/es060222i | year = 2006 | author = Williams, P.N. | last2 = Islam | first2 = M. R. | last3 = Adomako | first3 = E. E. | last4 = Raab | first4 = A. | last5 = Hossain | first5 = S. A. | last6 = Zhu | first6 = Y. G. | last7 = Feldmann | first7 = J. | last8 = Meharg | first8 = A. A.}}</ref><ref>*{{  cite journal
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| title = Screening of Rice Cultivars for Grain Arsenic Concentration and Speciation
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| journal = American Society of Agronomy Proceeding
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| author = Raghvan T
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}}</ref>
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==References==
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*1 Smedley PL, Kinniburgh DG (2002). "A review of the source, behaviour and distribution of arsenic in natural waters". Applied Geochemistry 17 (5): 517–568. doi:10.1016/S0883-2927(02)00018-5.
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*2 Mukherjee A., Sengupta M. K., Hossain M. A. (2006). "Arsenic contamination in groundwater: A global perspective with emphasis on the Asian scenario". Journal of Health Population and Nutrition 24 (2): 142–163.
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*3 Chowdhury U. K., Biswas B. K., Chowdhury T. R. (2000). "Groundwater arsenic contamination in Bangladesh and West Bengal, India". Environmental Health Perspectives (Brogan &#38) 108 (4): 393–397. doi:10.2307/3454378. JSTOR 3454378.
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*4 Jaymie R. Meliker, Arsenic in drinking water and cerebrovascular disease, diabetes mellitus, and kidney disease in Michigan: a standardized mortality ratio analysis Environmental Health Magazine. Volume 2:4. 2007. Accessed 9 Sept. 2008.
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*5 Ana Navas-Acien, "Arsenic Exposure and Prevalence of Type 2 Diabetes in US Adults," Journal of American Medical Association, v.300, n.7 (August 2008).
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*6 Singh A. K. (2006). "Chemistry of arsenic in groundwater of Ganges-Brahmaputra river basin". Current Science 91 (5): 599–606.
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*7 David Bradley, "Drinking the water of death", The Guardian, 5 January 1995
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*8 Amit Chatterjee, Dipankar Das, Badal K. Mandal, Tarit Roy Chowdhury, Gautam Samanta and Dipankar Chakraborti (1995). "Arsenic in ground water in six districts of West Bengal, India: the biggest arsenic calamity in the world. Part I. Arsenic species in drinking water and urine of the affected people". Analyst 120 (3): 643–651. doi:10.1039/AN9952000643.
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*9 Dipankar Das, Amit Chatterjee, Badal K. Mandal, Gautam Samanta, Dipankar Chakraborti and Bhabatosh Chanda (1995). "Arsenic in ground water in six districts of West Bengal, India: the biggest arsenic calamity in the world. Part 2. Arsenic concentration in drinking water, hair, nails, urine, skin-scale and liver tissue (biopsy) of the affected people". Analyst 120 (3): 917–925. doi:10.1039/AN9952000917. PMID 7741255.
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*10 New Scientist, Interview: Drinking at the west's toxic well 31 May 2006.
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*11 a b The Times of India, 'Use surface water. Stop digging', interview, 26 Sep, 2004.
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*12 a b World Health Organization, Arsenic in Drinking Water, accessed 5 Feb 2007.
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*13 P.L. Smedley, D.G. Kinniburgh, D.M.J. Macdonald, H.B. Nicolli, A.J. Barros, J.O. Tullio, J.M. Pearce, M.S. Alonso "Arsenic associations in sediments from the loess aquifer of La Pampa, Argentina" Applied Geochemistry 20 (2005) 989–1016. doi:10.1016/j.apgeochem.2004.10.005
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*14 Twarakavi, N. K. C., Kaluarachchi, J. J. (2006). "Arsenic in the shallow ground waters of conterminous United States: assessment, health risks, and costs for MCL compliance". Journal of American Water Resources Association 42 (2): 275–294. doi:10.1111/j.1752-1688.2006.tb03838.x.
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*15 Frederick Rubel Jr. and Steven W. Hathaway (1985) Pilot Study for removal of arsenic from drinking water at the Fallon, Nevada, Naval Air Station, Environmental Protection Agency, EPA/600/S2-85/094.
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*16 M. Taqueer A. Qureshi (1995) Sources of Arsenic in the Verde River and Salt River Watersheds, Arizona, M.S. thesis, Arizona State University, Tempe.
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*17 The history of arsenic regulation, Southwest Hydrology, May/June 2002, p.16.
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*18 EPA announces arsenic standard for drinking water of 10 parts per billion, EPA press release, 10/31/2001.
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*19 Alison Bohlen (2002) States move forward to meet new arsenic standard, Southwest Hydrology, May/June 2002, p.18-19.
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*20 Megan A. Ferguson and others, Lowering the detection limit for arsenic: implications for a future practical quantitation limit, American Water Works Association Journal, Aug. 2007, p.92-98.
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==External links==
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<!--*[http://iupac.org/publications/ci/2005/2704/pp1_2003-017-2-600.html Remediation Technologies for the Removal of Arsenic from Water and Wastewater] - Chemistry Journal  - no conclusions yet, have requested info - Singkong2005-->
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* [http://www.atsdr.cdc.gov/csem/arsenic/ ATSDR - Case Studies in Environmental Medicine: Arsenic Toxicity]
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* [http://www.igrac.net/publications/142 Arsenic in groundwater] IGRAC International Groundwater Resources Assessment Centre
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* [http://www.hydrology.nl/iahpublications/70-arsenic-in-groundwater.html Arsenic in Groundwater: A World Problem] - IAH publication, Netherlands National Chapter, 2008
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*[http://www.sos-arsenic.net SOS-Arsenic.net] - information and awareness raising site, focused on Bangladesh.
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*[http://www.sos-arsenic.net/english/contamin/smith.html Contamination of drinking-water by arsenic in Bangladesh: a public health emergency ] - at SOS-Arsenic.net
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* [http://www.insituarsenic.org Subterranean Arsenic Treatment Technology in West Bengal]
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* [http://www.worstpolluted.org/projects_reports/display/76 '''12 Cases of Cleanup & Success''']
 +
*[http://www.wbphed.gov.in/PHEDTables/arsenicbackground.html www.wbphed.gov.in] - Arsenic Scenario of West Bengal
 +
*[http://www.acdis.uiuc.edu/Research/OPs/Moinuddin/MoinuddinOP.pdf ''Drinking Death in Groundwater: Arsenic Contamination as a Threat to Water Security for Bangladesh''], ACDIS Occasional Paper by Mustafa Moinuddin
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*[http://www.st-andrews.ac.uk/news/archive/2010/Title,51258,en.html St Andrews Prize for Environment 2010]
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*[http://en.wikipedia.org/wiki/Arsenic_contamination_of_groundwater Arsenic contamination of groundwater] Wikipedia, March 2012

Latest revision as of 16:32, 12 March 2012

Arsenic contamination of groundwater is a natural occurring high concentration of arsenic in deeper levels of groundwater. It is a high-profile problem due to the use of deep tubewells 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.

Health effects of arsenic

Consuming water contaminated by arsenic can cause skin cancer, and bladder as well as cardiovascular disease.

Some research concludes that even at the lower concentrations, arsenic contamination is a major causes of death. A study conducted in a contiguous six-county area of southeastern Michigan investigated the relationship between moderate arsenic levels and 23 selected disease outcomes. Disease outcomes included several types of cancer, diseases of the circulatory and respiratory system, diabetes mellitus, and kidney and liver diseases. Elevated mortality rates were observed for all diseases of the circulatory system. The researchers acknowledged a need to replicate their findings.1

A preliminary study shows a relationship between arsenic exposure measured in urine and Type II diabetes. The results supported the hypothesis that low levels of exposure to inorganic arsenic in drinking water may play a role in diabetes prevalence.2

Arsenic in drinking water may also compromise immune function "Scientists link influenza A (H1N1) susceptibility to common levels of arsenic exposure"..

Contamination in Bangladesh and West Bengal, India

Arsenic contamination of the groundwater in Bangladesh is a serious problem. Prior to the 1970s, Bangladesh had one of the highest infant mortality rates in the world. Ineffective water purification and sewage systems as well as periodic monsoons and flooding exacerbated these problems. As a solution, UNICEF and the World Bank advocated the use of wells to tap into deeper groundwater. Millions of wells were constructed as a result. Because of this action, infant mortality and diarrheal illness were reduced by fifty percent. However, with over 8 million wells constructed, approximately one in five of these wells is now contaminated with arsenic above the government's drinking water standard.

In the Ganges Delta, the affected wells are typically more than 20 m and less than 100 m deep. Groundwater closer to the surface typically has spent a shorter time in the ground, therefore likely absorbing a lower concentration of arsenic; water deeper than 100 m is exposed to much older sediments which have already been depleted of arsenic.3

The crisis came to international attention in 1995.456 The study conducted in Bangladesh involved the analysis of thousands of water samples as well as hair, nail, and urine samples. They found 900 villages with arsenic above the government limit.

Criticism has been leveled at the aid agencies, who denied the problem during the 1990s while millions of tube wells were sunk. The aid agencies later hired foreign experts who recommended treatment plants that were inappropriate to the conditions, were regularly breaking down, or were not removing the arsenic.7

In West Bengal, India, water is mostly supplied from rivers. Groundwater comes from deep tubewells, which are few in number. Because of the low quantity of deep tubewells, the risk of arsenic patients in West Bengal is comparatively less.8 According to the World Health Organisation, “In Bangladesh, West Bengal (India), and some other areas most drinking-water used to be collected from open dug wells and ponds with little or no arsenic, but with contaminated water transmitting diseases such as diarrhoea, dysentery, typhoid, cholera, and hepatitis. Programmes to provide ‘safe’ drinking-water over the past 30 years have helped to control these diseases, but in some areas they have had the unexpected side-effect of exposing the population to another health problem—arsenic.”9 The acceptable level as defined by WHO for maximum concentrations of arsenic in safe drinking water is 0.01 mg/L. The Bangladesh government's standard is at a slightly higher rate, at 0.05 mg/L being considered safe. WHO has defined the areas under threat: Seven of the nineteen districts of West Bengal have been reported to have ground water arsenic concentrations above 0.05 mg/L. The total population in these seven districts is over 34 million while the number using arsenic-rich water is more than 1 million (above 0.05 mg/L). That number increases to 1.3 million when the concentration is above 0.01 mg/L. According to a British Geological Survey study in 1998 on shallow tube-wells in 61 of the 64 districts in Bangladesh, 46 percent of the samples were above 0.01 mg/L and 27 percent were above 0.050 mg/L. When combined with the estimated 1999 population, it was estimated that the number of people exposed to arsenic concentrations above 0.05 mg/L is 28-35 million and the number of those exposed to more than 0.01 mg/L is 46-57 million (BGS, 2000).9

Throughout Bangladesh, as tube wells get tested for concentrations of arsenic, ones which are found to have arsenic concentrations over the amount considered safe are painted red to warn residents that the water is not safe to drink.

One solution is “By using surface water and instituting effective withdrawal regulation. West Bengal and Bangladesh are flooded with surface water. We should first regulate proper watershed management. Treat and use available surface water, rain-water, and others. The way we're doing [it] at present is not advisable."8

Water purification solutions

Small-scale water treatment

A review of methods to remove arsenic from groundwater in Pakistan summarizes the most technically viable inexpensive methods.10

A simpler and less expensive form of arsenic removal is known as the Sono arsenic filter, using three pitchers containing cast iron turnings and sand in the first pitcher and wood activated carbon and sand in the second.11 Plastic buckets can also be used as filter containers.12 It is claimed that thousands of these systems are in use and can last for years while avoiding the toxic waste disposal problem inherent to conventional arsenic removal plants. Although novel, this filter has not been certified by any sanitary standards such as NSF, ANSI, WQA and does not avoid toxic waste disposal similar to any other iron removal process.

In the United States small "under the sink" units have been used to remove arsenic from drinking water. This option is called "point of use" treatment. The most common types of domestic treatment use the technologies of adsorption (using media such as Bayoxide E33, GFH, or titanium dioxide) or reverse osmosis. Ion exchange and activated alumina have been considered but not commonly used.

Large-scale water treatment

In some places, such as the United States, all the water supplied to residences by utilities must meet primary (health-based) drinking water standards. Regulations may necessitate large-scale treatment systems to remove arsenic from the water supply. The effectiveness of any method depends on the chemical makeup of a particular water supply. The aqueous chemistry of arsenic is complex, and may affect the removal rate that can be achieved by a particular process.

Some large utilities with multiple water supply wells could shut down those wells with high arsenic concentrations, and produce only from wells or surface water sources that meet the arsenic standard. Other utilities, however, especially small utilities with only a few wells, may have no available water supply that meets the arsenic standard.

Coagulation/filtration (also known as flocculation#Water_treatment|flocculation) removes arsenic by coprecipitation and adsorption using iron coagulants. Coagulation/filtration using alum is already used by some utilities to remove suspended solids and may be adjusted to remove arsenic. But the problem of this type of filtration system is that it gets clogged very easily, mostly within two to three months. The toxic arsenic sludge are disposed of by concrete stabilization, but there is no guarantee that they won't leach out in future.

Iron oxide adsorption filters the water through a granular medium containing ferric oxide. Ferric oxide has a high affinity for adsorbing dissolved metals such as arsenic. The iron oxide medium eventually becomes saturated, and must be replaced. The sludge disposal is a problem here too.

Activated alumina is an adsorbent that effectively removes arsenic. Activated alumina columns connected to shallow tube wells in India and Bangladesh have successfully removed both As(III) and As(V) from groundwater for decades. Long-term column performance has been possible through the efforts of community-elected water committees that collect a local water tax for funding operations and maintenance.13 It has also been used to remove undesirably high concentrations of fluoride.

Ion Exchange has long been used as a water-softening process, although usually on a single-home basis. Traditional anion exchange is effective in removing As(V), but not As (III), or arsenic trioxide, which doesn't have a net charge. Effective long-term ion exchange removal of arsenic requires a trained operator to maintain the column.

Both Reverse osmosis and electrodialysis (also called electrodialysis reversal) can remove arsenic with a net ionic charge. (Note that arsenic oxide, As2O3, is a common form of arsenic in groundwater that is soluble, but has no net charge.) Some utilities presently use one of these methods to reduce total dissolved solids and therefore improve taste. A problem with both methods is the production of high-salinity waste water, called brine, or concentrate, which then must be disposed of.

Subterranean Arsenic Removal (SAR) Technology SAR Technology

In subterranean arsenic removal (SAR), aerated groundwater is recharged back into the aquifer to create an oxidation zone which can trap iron and arsenic on the soil particles through adsorption process. The oxidation zone created by aerated water boosts the activity of the arsenic-oxidizing microorganisms which can oxidize arsenic from +3 to +5 state SAR Technology. No chemicals are used and almost no sludge is produced during operational stage since iron and arsenic compounds are rendered inactive in the aquifer itself. Thus toxic waste disposal and the risk of its future mobilization is prevented. Also, it has very long operational life, similar to the long lasting tube wells drawing water from the shallow aquifers.

Six such SAR plants, funded by the World Bank and constructed by Ramakrishna Vivekananda Mission, Barrackpore & Queen's University Belfast, UK are operating in West Bengal. Each plant has been delivering more than 3,000 litres of arsenic and iron-free water daily to the rural community. The first community water treatment plant based on SAR technology was set up at Kashimpore near Kolkata in 2004 by a team of European and Indian engineers led by Dr. Bhaskar Sen Gupta of Queen's University Belfast for TiPOT.14151617

SAR technology had been awarded Dhirubhai Ambani Award, 2010 from IChemE UK for Chemical Innovation. Again, SAR was the winner of the St. Andrews Award for Environment, 2010. The SAR Project was selected by the Blacksmith Institute - New York & Green Cross- Switzerland as one of the "12 Cases of Cleanup & Success" in the World's Worst Polluted Places Report 2009. (Refer: www.worstpolluted.org).

Currently, large scale SAR plants are being installed in USA, Malaysia, Cambodia, and Vietnam.

Dietary intake

Researchers from Bangladesh and the United Kingdom have recently claimed that dietary intake of arsenic adds a significant amount to total intake where contaminated water is used for irrigation.181920

References

  • 1 Smedley PL, Kinniburgh DG (2002). "A review of the source, behaviour and distribution of arsenic in natural waters". Applied Geochemistry 17 (5): 517–568. doi:10.1016/S0883-2927(02)00018-5.
  • 2 Mukherjee A., Sengupta M. K., Hossain M. A. (2006). "Arsenic contamination in groundwater: A global perspective with emphasis on the Asian scenario". Journal of Health Population and Nutrition 24 (2): 142–163.
  • 3 Chowdhury U. K., Biswas B. K., Chowdhury T. R. (2000). "Groundwater arsenic contamination in Bangladesh and West Bengal, India". Environmental Health Perspectives (Brogan &#38) 108 (4): 393–397. doi:10.2307/3454378. JSTOR 3454378.
  • 4 Jaymie R. Meliker, Arsenic in drinking water and cerebrovascular disease, diabetes mellitus, and kidney disease in Michigan: a standardized mortality ratio analysis Environmental Health Magazine. Volume 2:4. 2007. Accessed 9 Sept. 2008.
  • 5 Ana Navas-Acien, "Arsenic Exposure and Prevalence of Type 2 Diabetes in US Adults," Journal of American Medical Association, v.300, n.7 (August 2008).
  • 6 Singh A. K. (2006). "Chemistry of arsenic in groundwater of Ganges-Brahmaputra river basin". Current Science 91 (5): 599–606.
  • 7 David Bradley, "Drinking the water of death", The Guardian, 5 January 1995
  • 8 Amit Chatterjee, Dipankar Das, Badal K. Mandal, Tarit Roy Chowdhury, Gautam Samanta and Dipankar Chakraborti (1995). "Arsenic in ground water in six districts of West Bengal, India: the biggest arsenic calamity in the world. Part I. Arsenic species in drinking water and urine of the affected people". Analyst 120 (3): 643–651. doi:10.1039/AN9952000643.
  • 9 Dipankar Das, Amit Chatterjee, Badal K. Mandal, Gautam Samanta, Dipankar Chakraborti and Bhabatosh Chanda (1995). "Arsenic in ground water in six districts of West Bengal, India: the biggest arsenic calamity in the world. Part 2. Arsenic concentration in drinking water, hair, nails, urine, skin-scale and liver tissue (biopsy) of the affected people". Analyst 120 (3): 917–925. doi:10.1039/AN9952000917. PMID 7741255.
  • 10 New Scientist, Interview: Drinking at the west's toxic well 31 May 2006.
  • 11 a b The Times of India, 'Use surface water. Stop digging', interview, 26 Sep, 2004.
  • 12 a b World Health Organization, Arsenic in Drinking Water, accessed 5 Feb 2007.
  • 13 P.L. Smedley, D.G. Kinniburgh, D.M.J. Macdonald, H.B. Nicolli, A.J. Barros, J.O. Tullio, J.M. Pearce, M.S. Alonso "Arsenic associations in sediments from the loess aquifer of La Pampa, Argentina" Applied Geochemistry 20 (2005) 989–1016. doi:10.1016/j.apgeochem.2004.10.005
  • 14 Twarakavi, N. K. C., Kaluarachchi, J. J. (2006). "Arsenic in the shallow ground waters of conterminous United States: assessment, health risks, and costs for MCL compliance". Journal of American Water Resources Association 42 (2): 275–294. doi:10.1111/j.1752-1688.2006.tb03838.x.
  • 15 Frederick Rubel Jr. and Steven W. Hathaway (1985) Pilot Study for removal of arsenic from drinking water at the Fallon, Nevada, Naval Air Station, Environmental Protection Agency, EPA/600/S2-85/094.
  • 16 M. Taqueer A. Qureshi (1995) Sources of Arsenic in the Verde River and Salt River Watersheds, Arizona, M.S. thesis, Arizona State University, Tempe.
  • 17 The history of arsenic regulation, Southwest Hydrology, May/June 2002, p.16.
  • 18 EPA announces arsenic standard for drinking water of 10 parts per billion, EPA press release, 10/31/2001.
  • 19 Alison Bohlen (2002) States move forward to meet new arsenic standard, Southwest Hydrology, May/June 2002, p.18-19.
  • 20 Megan A. Ferguson and others, Lowering the detection limit for arsenic: implications for a future practical quantitation limit, American Water Works Association Journal, Aug. 2007, p.92-98.

External links

  • ↑ , Jaymie R. Meliker, Arsenic in drinking water and cerebrovascular disease, diabetes mellitus, and kidney disease in Michigan: a standardized mortality ratio analysis Environmental Health Magazine. Volume 2:4. 2007. Accessed 9 Sept. 2008.
  • ↑ Ana Navas-Acien, "Arsenic Exposure and Prevalence of Type 2 Diabetes in US Adults," Journal of American Medical Association, v.300, n.7 (August 2008).
  • ↑ Template:Cite journal
  • ↑ David Bradley, "Drinking the water of death", The Guardian, 5 January 1995
  • ↑ Template:Cite journal
  • ↑ Template:Cite journal
  • ↑ New Scientist, Interview: Drinking at the west's toxic well 31 May 2006.
  • ↑ 8.0 8.1 The Times of India, 'Use surface water. Stop digging', interview, 26 Sep, 2004.
  • ↑ 9.0 9.1 World Health Organization, Arsenic in Drinking Water, accessed 5 Feb 2007.
  • ↑ Fatima Hashmi and Joshua M. Pearce, “Viability of Small-Scale Arsenic-Contaminated Water Purification Technologies for Sustainable Development in Pakistan”, Sustainable Development, 19(4), pp. 223-234, 2011. pdf Open access full text
  • ↑ Template:PDFlink
  • ↑ Template:PDFlink - pictures with descriptions.
  • ↑ Template:Cite journal
  • ↑ 12 Cases of Cleanup & Success
  • ↑ "World's Worst Polluted Places Report 2009"
  • ↑ Scientific American
  • ↑ Reuters Global
  • ↑ Template:Cite news
  • ↑ Template:Cite journal
  • ↑ *Template:Cite journal
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