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

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.

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.

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/cm3

Liquid density at m.p

5.22g/cm3

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

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

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.

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).

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)

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

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.

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

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)

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).

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 2HAsO42- + 3SO4

2- + 10H+

AsS + 2.75O2 + 2.5H2O HAsO42- +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

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).

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

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).

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

PEOPLE SUFFERNING FROM ARSENIC POISONING

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

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.

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