arsenic contamination of groundwater

1. Arsenic Contamination Of Groundwater
Seminar Report 2012-13

Department of Civil Engineering
Indian Institute of Technology
Banaras Hindu University



Under the guidance of: Submitted by:
Prof. Devendra Mohan Mayank Saxena
09103EN008
B.Tech, Part-IV

2. ABSTRACT

Natural groundwater arsenic-contamination and the sufferings of people as a result, has become a
crucial water quality problem in many parts of the world, particularly in Bengal delta, Bangladesh and
West Bengal (India). It has recently been recognized that As-contaminated groundwater used for
irrigation may pose an equally serious health hazard to people eating food from the crops irrigated and
that As accumulating in irrigated soils poses a serious threat to sustainable agriculture in affected areas.
This report reviews the nature of those threats, taking into account the natural and anthropogenic
sources of arsenic pollution, areas affected and health impact of arsenic contamination of groundwater.

3. ACKNOWLEDGEMENT
Apart from one’s own effort, the success of any work largely depends on the encouragement and
guidance of the others. I would like to take this opportunity to express my gratitude to the people
instrumental in the successful completion of this report
My special thanks to Prof. Devendra Mohan ( Department of civil engineering,IIT-BHU) for mentoring
my report. I show my greatest appreciation to him for his tremendous support and help. I feel motivated
and encouraged after working under his guidance and without whom this project would not have been
materialized.
I would also like to acknowledge and extend my heartiest gratitude to my classmates Mr. Ayush
Agarwal, Mr. Bhuvanesh Shukla and Mr. Deepak Kumar who gave important suggestions and
tremendous support which was very vital for success of my report.

4. 1. INTRODUCTION

Arsenic is a chemical element with symbol As and atomic number 33. Arsenic occurs in many minerals,
usually in conjunction with sulfur and metals, and also as a pure elemental crystal. Arsenic is a metalloid.
It can exist in various allotropes, although only the gray form has important use in industry. Arsenic is
notoriously poisonous to multicellular life, although a few species of bacteria are able to use arsenic
compounds as respiratory metabolites. Various physical and chemical properties of arsenic are as
follows-
1.1 PHYSICAL PROPERTIES OF ARSENIC
Arsenic occurs in three most common allotropes which are metallic grey, yellow and black arsenic, with
gray being the most common. Gray arsenic adopts a double-layered structure consisting of many
interlocked ruffled six-membered rings. 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.[8] This relatively close packing leads to a high density of 5.73 g/cm3. Gray 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 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 vapor, As4. It is
rapidly transformed into the gray arsenic by light. The yellow form has a density of 1.97 g/cm3.


Phase solid
Density 5.727g/cm
3

Liquid density at
m.p
5.22g/cm
3

Sublimation Point 881K
Triple point 1090K, 3628 kPa

Heat of Fusion 24.44kJ/mole
Heat of Vaporization 34.76kJ/mole
Sublimation Point 881K

Physical Properties of Arsenic

5. 1.2. CHEMICAL PROPERTIES
Arsenic is a member of Va group of periodic table. It occur in nature in four oxidation states -3,0,+3,+5
with -3 being most toxic and +5 being least toxic. In groundwater, Arsenic is found in only two oxidation
states i.e +3 and +5. Various chemical properties of Arsenic are summarize in the following table

Symbol As
Atomic number 33
Element category Metalloid
Group,period,block Va,4,p
Atomic weight 74.92160
Electronegativity 2.18(pauling scale)
Atomic radius 119 pm
Van der Waals radius 185 pm

CHEMICAL PROPERTIES OF ARSENIC

1.3 ARSENIC CONTAMINATION OF GROUNDWATER
Arsenic contamination of groundwater is a natural occurring high concentration of arsenic in deeper
levels of groundwater. As per WHO, maximum permissible limit of arsenic in groundwater is 10 µg/liter.
Arsenic contamination poses a serious health hazard to about 150 million people worldwide
(Ravenscroft et al. 2009). Around 110 million of those people live in ten countries in South and South-
east Asia: Bangladesh, Cambodia, China, India, Laos, Myanmar, Nepal, Pakistan, Taiwan and Vietnam
(Brammer and Ravenscroft, 2009). Recently it has also been found that As-contaminated groundwater
used for irrigation may pose an equally serious health hazard to people eating food from the crops
irrigated and that As accumulating in irrigated soils poses a serious threat to sustainable agriculture in
affected areas. Arsenic is found in nature in soils and rocks, natural waters and organisms. It is mobilized
through a combination of natural processes such as weathering reactions, biological activity and volcanic
emissions as well as through a range of anthropogenic activities. Most environmental As problems are
the result of mobilization under natural conditions. However, man has had an important additional

6. impact through mining activity, combustion of fossil fuels, the use of arsenical pesticides, herbicides and
crop desiccants.

2. DISTRIBUTION OF ARSENIC
2.1 CONTINENT-WISE DISTRIBUTION
2.1.1 ASIA
Main areas affected from arsenic contamination of groundwater in Asia are Xinjiang, Liaoning, Jilin,
inner Mongolia, Ningxia, Shanxi, Jhelum basin (Pakistan), Bangladesh, Nepal, Guizhou (China), Taiwan,
Hanoi (Vietnam), Myanmar, West Bengal (India), Uttar Pradesh (India) , Cambodia, Ronphibun
(Thailand), Gujarat (India) (Chakraborti et al,2002).

DISTRIBUTION OF ARSENIC IN ASIA
1) Xinjiang; (2) Jilin; (3) Liaoning; (4) inner Mongolia; (5) Ningxia; (6) Shanxi, all foregoing in China; (7) Jhelum, Pakistan; (8)
Pakistan; (9) Bangladesh; (10) Nepal; (11) Guizhou, China; (12) Taiwan; (13) Hanoi, Vietnam; (14) Myanmar; (15) Lao PDR;
(16) WB, India; (17) Cambodia; (18) Ronphibun, Thailand.

7. 2.1.2 EUROPE
In Europe, problem of arsenic contamination of groundwater is less as compared to Asia. Major
European countries affected from this problem are Hungary, Romania and South-west Finland. In
Hungary concentration of arsenic in groundwater is 1-174 µg.L
-1
, in Romania, concentration is about 1-
176 µg.L
-1
(Sharma and Sohn, 2009).

2.1.3 AUSTRALIA
Australia is a country rich in minerals that constitute a significant source of arsenic contamination to the
environment, in addition to anthropogenic sources, such as mining activities and pesticide usage. In
1991, survey data revealed elevated levels of arsenic in surface water and groundwater of Victoria
(Mukherjee et al, 2006).
2.1.5 NORTH AMERICA
Some locations in the United States, such as Fallon, Nevada, have long been known to have
groundwater with relatively high arsenic concentrations (in excess of 0.08 mg/L). Even some surface
waters, such as the Verde River in Arizona, sometimes exceed 0.01 mg/L arsenic, especially during low-
flow periods when the river flow is dominated by groundwater discharge.( Taqueer and Quereshi, 1995).
Other Affected areas in North America are Hermosillo, Yaqui river watershed, Valle del Guadiana,
Morales in San Luis Potosi city, Puebla state, Taxco, Pol Chucabkatun, Luna-Sen, Salamanca, Acambaro,
Zacatecas, Santa Ma. De la Paz, Puebla state (Bundschuh et al, 2012).

2.1.4 SOUTH AMERICA
Areas of South America affected from arsenic contamination are Chile, Brazil, Argentina, Peru, Ecuador,
Tambo river and Papallacta lake area, Tumbaco, Locumba Valley, Quebrada de Camarones, Tatio
Geothermal springs, upper Pilcomayo river basin, Garayalde ( Uruguay), Santa Barbara dist. , Rimac river
basin, Geothermal water from EL Carchi, Imbabura, Pichincha, Cotopaxi, Puno, Lluta and Azata valleys,
Morococha mining region (Bundschuh et al, 2012).

8. DISTRIBUTION OF ARSENIC IN SOUTH AMERICA
(76) Loa riverbasin/Atacamadesert, (77) Tatiogeothermal springs,(78) Coquimbo,Valle del Elqui,(79) Maipu river basin;Bolivia: (80) El Alto(La
Paz), (81) Oruro,(82) Poopó basin, (83) North ofPotosí dept., (84) Upper Pilcomayoriver basin; (85) Lipéz and south ofPotosí dep.; Argentina:
(86) NWArgentine Andean highland, e.g.San Antonio de Los Cobres andmany other localities, (87) Chaco plain,(88) Pampa plain, (89)
Copahue,(90) Garayalde and Camarones(Chubut prov.); Uruguay: (91) San Josédept.; Brazil: Minas Gerais st.: (92)Nova Lima dist., (93) Santa
Bárbaradist., (94) Ouro Preto/Mariana dist. (63) El diamantegold mine; Caldas dep.; Ecuador: (64) Tamboriver and Papallacta lake area
(Quijos county,Napo prov.), (65) Guayllabamba, (66)Tumbaco, (67) Geothermal waters from ElCarchi, Imbabura, Pichincha, Cotopaxi,
andTungurahua prov.; Peru: (68)Morococha miningregion/La Oroya smelting complex (Yauli prov,Junin dep.), (69) Rímac river basin,
(70)Huaytará prov. (Huancavélica dep.), (71) Puno(Puno dep.), (72) Locumba valley (Tacna dep.;Ilo city water supply), (74) Arica area(Lluta
and Azapavalleys, (75) Quebradade Camarones (73)Tacna area (SamaQuebrada de la Yarada)

9. 2.1.6 AFRICA
Areas affected from arsenic contamination in Africa are Obuasi and Bolgatunga regions of Ghana
(Smedley, 1996). Other areas are Yatenga, Ankobra basin, Offin basin, Ekondo Titi, Okavango Delta
(Ravenscroft, 2007)

DISTRIBUTION OF ARSENIC IN AFRICA

10. 2.2 DISTRIBUTION OF ARSENIC IN INDIAN SUB-CONTINENT
2.2.1 PAKISTAN
Areas affected from arsenic contamination in Pakistan include Manchar Lake Jamshoro (Sindh), some
parts of Ravi basin, Sialkot, Kasur city, Muzaffargarh, Multan, Karachi (Azizullah et al, 2011).

Location Conc. Of
As(in ug.L
-1
)
Reference
Various spots
of Karachi

Well water of
Multan

Muzzafargarh
Manchar
Lake


2.2.2 SRI LANKA
Areas affected from arsenic contamination in SriLanka are Rajarata, Anuradhapura and some parts of
Colombo (Jayasumana et al, 2007).
2.2.3 NEPAL
Major areas affected from arsenic contamination in Nepal are Nawalparasi, Bara, Parsa, Rautahat,
Rupandehi, Kapilvastu, Rautahat, and Kailali with concentration between 50-2621 µg/l (Pokhrel et al,
2007).
2.2.4 BANGLADESH
Major areas affected from arsenic contamination are Sylhet, Brahmanbaria, Mymensingh, Narayanganj,
Sherpur, Bogra, Netrokona, Kishoreganj, Meherpur, Thakurgaon, Moulavibazar, Comilla, Madaripur,
Chittagong, Rangamati, Khulna, Thakurgaon, Panchagarh, Sirajganj, Rangpur.

11. DISTRIBUTION OF ARSENIC IN BANGLADESH (adapted from Chakraborti et al, 2007)

12. 2.2.5 INDIA
2.2.5.1 WEST BENGAL
Malda, Murshidabad, Nadia, North Parganas, Parganas, Bardhaman, Howrah, Hoogly and Kolkata have
concentration more than 300 µg/l. Kooch Bihar, Jalpaiguri, Darjeeling, North Dinajpur and South
Dinajpur have concentration about 50µg/l (Chakraborti et al, 2007).

DISTRIBUTION OF ARSENIC IN WEST BENGAL (adapted from Chakraborti et al, 2001)

13. 2.2.5.2 UTTAR PRADESH
Main areas affected from arsenic contamination in Uttar Pradesh are Varanasi, Gazipur and ballia. The
area and population of the 3affected districts are 11450 km2 (4.8 % of the total area of UP) and
8.7million, approximately 5.3 % of the total population of UP (Chakraborti et al).
2.2.5.3 BIHAR
Main areas affected from arsenic contamination in Bihar are Chakani village (Brahampur) and Barahara
block in Buxar district. There is also a probability of arsenic contamination in districts close to arsenic
contaminated Tarai region of Nepal.
2.2.5.4 OTHERS
Others areas contaminated from arsenic in India are Sahibganj district of Jharkhand, Imphal East, Imphal
West, Thoubal and Bishnupur (Manipur) (Chakraborti et al), Rajnandgaon and Kanker District
(Chattisgarh) (Shukla et al, 2009).


3. SOURCES OF ARSENIC
3.1 ARSENIC MOBILIZATION MECHANISM
Four mechanisms have been proposed for the mobilization of arsenic into ground water
 Reductive dissolution
 Alkali desorption
 Geothermal action
 Sulphide oxidation
3.1.1 REDUCTIVE DISSOLUTION
Iron (III) oxyhydroxides are of particular environmental relevance because they often occur as fine
grained particles and exhibit high reactive surfaces. The Fe(II)/Fe(III) redox couple is an important
electron-transfer mediator for many biological and chemical species. As a consequence, the stability of
Fe(III) oxyhydroxides in soils exerts a major control on mobility of both organic and inorganic pollutants
such as arsenic. Iron-reducing bacteria — which are present in waterlogged soils and aquifers — couple
the oxidation of organic matter with the reduction of various Fe(III) oxyhydroxides for their metabolism.
A direct consequence of Fe(III) reduction is the associated trace metal release into soil solution (Fakih et
al,2009).

14. 3.1.2 ALKALI DESORPTION
Laboratory studies show that arsenic adsorbed to iron, manganese and aluminum oxides and clay
minerals may be desorbed at pH >8.0, leaving the carrier phase as a solid. The best-documented
example comes from the southwest USA (Baxfield and Plummer, 2003), and others come from
Oklahoma, Spain, China and from volcanic deposits in Argentina (Nicolli et al, 1989).

3.1.3 SULPHIDE OXIDATION

Arsenic sulfide minerals such as orpiment and realgar are of significant economic interest in many
mining operations because of their role as reliable indicators of gold mineralization .These minerals are
also of great environmental interest because the oxidative dissolution of these minerals can potentially
increase the concentrations of As in natural water ( Lengke and Tempel, 2004). The proposed overall
reactions of arsenic sulfide oxidation are written as:
As2S3 + 7O2 + 6H2O  2HAsO4
2-
+ 3SO4
2-
+ 10H
+

AsS + 2.75O2 + 2.5H2O HAsO4
2-
+SO4
2-
+ 4H
+


3.1.4 GEOTHERMAL ACTION
Mixing of geothermal solutions and fresh ground water can lead to high arsenic concentrations in some
locations (Smedley and Kinniburgh, 2002).

3.2 MAJOR AREAS CONTAMINATED FROM ARSENIC AND ARSENIC
MOBILIZATION MECHANISM INVOLVED

Contaminated Areas

Mechanism involved References
West Bengal

Reductive dissolution Harvey et al,2004
Bangladesh Reductive dissolution and in
some parts geochemical
Harvey et al,2004;
Anawar et al 2001
South-West USA

Alkali desorption Baxfield and Plummer, 2003
Perth (Australia) Sulphide Oxidation Appleyard et al,2006

15. Mid-West USA

Reductive Dissolution Kelly et al,2005
Spain Alkali Desorption Ravenscroft 2007

Argentina Alkali Desorption Nicolli et al,1989

Danube (Europe)

Reductive dissolution Kelly et al, 2005
China Alkali desorption Ravenscroft 2007

Chile (South America) Geothermal activity Smith et al,1998

Tibet plateau Geothermal activity Ravenscroft 2007

Ghana (Africa) Sulphide oxidation Smedley 1995


3.3 ANTHROPOLOGICAL ACTIVITIES LEADING TO ARSENIC
CONTAMINATION OF GROUNDWATER
Many compounds of arsenic are used in various field which have a potential to spread arsenic
contamination. Some of the major compounds are:
3.3.1 CHROMATED COPPER ARSENATE
Chromated copper arsenate (CCA) has been long used for treating wood in order to increase its lifetime
in outdoor applications. It had been observed that the chemical and structural forms of either Cr or As in
the exposed wood are the same as in freshly treated material (Nico et al,2004). The leaching of dislodge
abled residues of CCA-preserved wood with simulated biological fluids (sweat or gastric juice) indicated
the main presence of free As(V) anionic species. Another source of As comes from CCA-impregnating
plants, whose soils may contain high pools of potential contamination.
3.3.2 4-HYDROXY-3-NITROBENZENE ARSONIC ACID (ROXARSONE)
The common use of antibiotic additive Roxarsone is in poultry farm to increase the chicken weight.
However As is largely excreted and consequently poultry litter can contain high As levels (Villaescusa
and Bollinger,2007): up to 40 mg/kg (dry weight). Moreover such As from poultry litter is easily water
soluble with 70–90% extraction rate (Garbarino et al.2003; Rutherford et al. 2003), and transformed to
As(V) due to both photo degradation and mineralization in the presence of nitrate and organic matter
(Bednar et al. 2003).

16. 3.3.3 MONOSODIUM METHANEARSONATE (MSMA)
It a common arsenical herbicide used in golf course green treatment, led to a systematic monitoring of
related soils and the water percolating through these soils .Presumably due to microbial activity in the
soil, MSMA was found to be transformed to As(V),As(III), MMA and DMA; after 14 weeks, almost20% of
inorganic As originating from MSMA can percolate below the rhizosphere (Villaescusa and
Bollinger,2008).

 Other anthropological causes of arsenic contamination are not yet verified but it is hypothesized
that excessive use of groundwater create an environment which favors arsenic mobilization
through soil.
 Improper disposal of mining wastes also causes the groundwater contamination in mining areas.

4. IMPACTS OF ARSENIC CONTAMINATION
Before discussing about the impacts of arsenic contamination let us first discuss about the toxicity of
two arsenic species: As(III) and As(IV) present in groundwater.
4.1 TOXICITY OF ARSENIC
It is commonly accepted that inorganic As(III) compounds are approximately 60–80 times more toxic to
humans than As(V) ones (Villaescusa and Bollinger,2008). The acute toxicity of arsenic is related to its
chemical form and oxidation state. Toxicity of any chemical species is measured in LD50 (LD50 with
respect to any biological species is the amount required to kill 50% of a given test species.). Toxicity level
of some arsenic compounds are shown in the table.
CHEMICAL SPECIES (sex) LD50 (mg/kg) REFERNCES

Arsenite Mouse (male) 8 Bencko et al,1978
Arsenite Hamster (male) 8 Petrick et al,2001
Arsenate Mouse (male) 22 Bencko et al,1978
Arsenobetaine Mouse (male) >4260 Kaise et al, 1985

17. Arsenic trioxide Mouse (male) 26-48 Harrison et al, 1958
MMA Hamster (male) 2 Petrick et al,2001
DMA Mouse (male) 648 Kaise et al, 1985
TMAO Mouse (male) 5500 Kaise et al, 1985

4.1.1 MECHANISM OF PENTAVALENT ARSENIC TOXICITY
Arsenate can replace phosphate in many biochemical reactions because they have similar structure and
properties (Hughes, 2001). For example:
 Arsenate reacts in vitro with glucose and gluconate to formglucose-6-arsenate and 6-
arsenogluconate, respectively. These compounds resemble glucose-6-phosphate and 6-
phosphogluconate, respectively.

 Arsenate can also replace phosphate in the sodium pump and the anion exchange transport
system of the human red blood cell (Hughes, 2001).

 Arsenate uncouples in vitro formation ofadenosine-5-triphosphate (ATP) by a mechanism
termed arsenolysis. Depletion of ATP by arsenate has been observed in cellular systems. ATP
levels are reduced in human erythrocytes (Winski and Carter,1998) after in vitro exposure to
arsenate.
4.1.2 MECHANISM OF TRIVALENT ARSENIC TOXICITY
Specific functional groups within enzymes, receptors or coenzymes, such as thiols or vicinal sulfhydryls,
have a major role in the activity of these molecules. Trivalent arsenic readily react in vitro with these
thiol-containing molecules (Hughes,2001). The binding of trivalent arsenic to critical thiol groups may
inhibit important biochemical events which could lead to toxicity. Pyruvate dehydrogenase (PDH) is a
multi-subunit complex that requires lipoic acid (a dithiol) for enzymatic activity so arsenite inhibits PDH
by binding to the lipoic acid which ultimately leads to the decreased production of ATP (Hughes,2001).

18. 4.2 WHY IS ARSENIC BAD FOR HEALTH?
Arsenic dissolved in water is acutely toxic and can lead to a number of health problems. Long-term
exposure to arsenic in drinking-water causes increased risks of cancer in the skin, lungs, bladder and
kidney. It also leads to other skin-related problems such hyperkeratosis and changes in pigmentation.
Consumption of arsenic also leads to disturbance of the cardiovascular and nervous system functions
and eventually leads to death. Increased risks of lung and bladder cancer and of arsenic-associated skin
lesions have been reported for consuming drinking-water with arsenic concentrations equal to or
greater than 50 parts per billion (or microgram per liter). (WHO Environmental Health Criteria).
Arsenicosis, or arsenic toxicity, develops after two to five years of exposure to arsenic contaminated
drinking water, depending on the amount of water consumption and arsenic concentration in water.
Initially, the skin begins to darken (called diffuse melanosis). This happens first in the palms. Diffuse
melanosis leads to spotted melanosis, when darkened spots begin to appear on the chest, back and
limbs, although the latter is what is usual among people, and so is taken to be an early symptom. At a
later stage, leucomelanosis sets in: the body begins to show black and white spots.
Keratosis is the middle stage of arsenicosis. The skin, in portions, becomes hard and fibrous; it is as if the
body has broken out into hard boils, or ulcers. Diffuse or nodular keratosis on the palm of the hand or
sole of the foot is a sign of moderately severe toxicity. Rough dry skin, often with palpable nodules on
hands, feet and legs means severe toxicity. This can lead to the formation of gangrene, and cancer.
Arsenic poisoning brings with it other complications: liver and spleen enlargement and cirrhosis of the
liver; myocardial degeneration and cardiac failure; peripheral neuropathy affecting primary sensory
functions; diabetes mellitus and goiter. Another unfortunate and complicating fact about arsenic
poisoning, is that it generally takes from seven to 10 years sometimes longer, for the disease to be
recognized. When it finally is, it may be too late to treat.
SYSTEM EFFECT

Skin Skin Lesions

Cardiovascular Blackfoot disease

Nervous Peripheral neuropathy, Encephalopathy

Endocrine Diabetes

Renal Proximal tubule degeneration, papillary
and cortical necrosis

Hematological Bone marrow depression


ADAPTED FROM HUGHES,2002

19. PEOPLE SUFFERNING FROM ARSENIC POISONING

20. UPTAKE


























HUMAN EXPOSURE TO EXPOSURE AND VARIOUS MODE OF ARSENIC TOXICITY ( adapted from Roy and Saha)

MINING/
COALBURNING
NATURAL
DEPOSITS/SOILS
DRINKING
WATER/FOOD
HUMAN EXPOSURE TO ARSENIC
CELLULAR METABOLISM/TOXICITY
EXCRETION
ACCUMULATION
CARCINOGEN
NON-CARCINOGEN
CHROMOSOMAL ABNORMALITIES
OXIDATIVE STRESS
ABERRATIONS IN GENE EXPRESSION
MODIFICATION OF CELL PROLIFERATION
CARDIOVASCULAR
AND NON-
CARDIOVASCULAR
AFFECTS

21. CONCLUSION
This review, based on a large number of accessible sources of information on As contamination in
groundwater suggests that arsenic contamination is highest in South and South-East Asia and lowest in
Africa. Most of the sources of arsenic contamination are natural whereas anthropological activities work
as a catalyst in the mobilization of arsenic. Various mechanisms for mobilization of arsenic through soil
are proposed which depends mainly upon the hydro-geochemical properties of the area. Inorganic
arsenic is a carcinogen for human (not yet proved for animals) and it also causes various cardiovascular
and vascular diseases to human. About 137 million people in more than 70 countries are probably
affected by arsenic poisoning of drinking water, so it is very important to take measures to reduce the
arsenic concentration in groundwater on a large scale. Reverse Osmosis filter system should be installed
in households to avoid arsenic poisoning.

22. REFERENCES

 Hugh Brammer, Peter Ravenscroft, 2008. Arsenic in groundwater: A threat to
sustainable agriculture in South and South-east Asia.
 Dipankar Chakraborti , Mohammad Mahmudur Rahman , Bhaskar Das ,Matthew Murrill
, Sankar Dey , Subhas Chandra Mukherjee , Ratan Kumar Dhar ,Bhajan Kumar Biswas ,
Uttam Kumar Chowdhury , Shibtosh Roy , Shahariar Sorif ,Mohammad Selim ,
Mahmuder Rahman , Quazi Quamruzzaman,2010. Status of groundwater arsenic
contamination in Bangladesh: A 14-year study report
 H.M. Anawar, J. Akaib, K.M.G. Mostofa, S. Safiullah, S.M. Tareq, 2001. Arsenic poisoning
in groundwater:Health risk and geochemical sources in Bangladesh
 Virender K. Sharma, Mary Sohn, 2009. Aquatic arsenic: Toxicity, speciation,
transformations, and remediation
 Dipankar Chakraborti , Mohammad M. Rahman , Kunal Paul ,Uttam K. Chowdhury ,
Mrinal K. Sengupta , Dilip Lodh ,Chitta R. Chanda , Kshitish C. Saha , Subhash C.
Mukherjee,2001. Arsenic calamity in the Indian subcontinent: What lessons have been
learned?
 P.L. Smedley, D.G. Kinniburgh,2001. A review of the source, behaviour and distribution
of arsenic in natural waters
 Dericks Praise Shukla , C.S. Dubey , Ningthoujam P. Singh , M. Tajbakhsh , M.
Chaudhry,2010. Sources and controls of Arsenic contamination in groundwater of
Rajnandgaon and Kanker District, Chattisgarh, Central India
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Nicolli ,Jiin-Shuh Jean, Chen-Wuing Liu , Dina López , María A. Armienta , Luiz R.G.
Guilherme, Alina Gomez Cuevas , Lorena Cornejo , Luis Cumbal , Regla Toujaguez,2011.
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from 14 countries
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 http://en.wikipedia.org/wiki/Arsenic
 http://en.wikipedia.org/wiki/Arsenic_poisoning
 http://water.epa.gov/lawsregs/rulesregs/sdwa/arsenic/index.cfm