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Evaluation of high levels of fluoride, arsenic species and otherphysicochemical parameters in underground water of two subdistricts of Tharparkar, Pakistan: A multivariate study

Kapil Dev Brahman a,1, Tasneem Gul Kazi a,*, Hassan Imran Afridi a,1, Shahid Naseem b,2,Sadaf Sadia Arain a,1, Naeem Ullah a,1

aNational Center of Excellence in Analytical Chemistry, Department of Analytical Chemistry, University of Sindh, Jamshoro,

Sindh 76080, PakistanbDepartment of Geology, University of Karachi, Karachi 75270, Pakistan

a r t i c l e i n f o

Article history:

Received 2 July 2012

Received in revised form

23 October 2012

Accepted 26 October 2012

Available online 21 November 2012

Keywords:

Arsenic

Fluoride

Speciation

Sodium absorption ratio

Saturation index

Thar dessert

* Corresponding author. Tel.: þ92 022 277137E-mail addresses: kr_brahman@yahoo

(H.I. Afridi), sngeo@yahoo.com (S. Naseem1 Tel.: þ92 022 2771379; fax: þ92 022 277152 Tel.: þ92 21 99261311.

0043-1354/$ e see front matter ª 2012 Elsevhttp://dx.doi.org/10.1016/j.watres.2012.10.042

a b s t r a c t

In present study total arsenic, inorganic arsenic species and fluoride ion contaminations in

underground water of Diplo and Chachro sub district of Tharparkar, Pakistan were

investigated. The concentrations of total As, inorganic As species, F� and others physico-

chemical parameters were reported in terms of basic statistical parameters, principal

component analysis, cluster analysis, sodium absorption ratio and saturation indices. The

As3þ was determined by cloud point extraction using ammonium pyrrolidinedithiocarba-

mate (APDC) as complexing reagent, and complex was extracted by surfactant-rich phases

in the non-ionic surfactant Triton X-114; after centrifugation the surfactant-rich phase was

diluted with 0.1 mol/L HNO3 in methanol. While total inorganic arsenic (iAs) was

determined by solid phase extraction using titanium dioxide (TiO2) as an adsorbent, after

centrifugation, the solid phase was prepared to be slurry for determination. The extracted

As species were determined by electrothermal atomic absorption spectrometry. The

concentration of As5þ in the water samples was calculated by the difference of the total iAs

and As3þ, while F� and other anions were determined by ion chromatography. The positive

correlation of F� and As species with Naþ and HCO�3 showed that the water with high

salinity and alkalinity stabilized the As species and F� in the groundwater. The

positive correlation (r ¼ 0.640, p ¼ 0.671) was observed between total As and it species with

F�. Results showed that underground water samples of these two areas of Tharparkar were

severely contaminated with arsenic and fluoride ion, which are exceeded the World Health

Organization (WHO) provisional guideline value, and United States Environmental

Protection Agency, maximum contaminant level of 0.01 mg/L and 1.5 mg/L, respectively.

ª 2012 Elsevier Ltd. All rights reserved.

9; fax: þ92 022 2771560..com (K.D. Brahman), tgkazi@yahoo.com (T.G. Kazi), hassanimranafridi@yahoo.com), ssadiashafi@gmail.com (S.S. Arain), khannaeemullah@ymail.com (N. Ullah).

60.

ier Ltd. All rights reserved.

wat e r r e s e a r c h 4 7 ( 2 0 1 3 ) 1 0 0 5e1 0 2 01006

1. Introduction separation and pre-concentration methods reported in the

The quality of groundwater depends on various chemical

constituents and their concentration, which are mostly

derived from the geological data of the particular region. It is

estimated that approximately one third of the Worlds pop-

ulation use groundwater for drinking (UNEP, 1999). Arsenic

(As) and Fluoride (F�) in thewater is a serious natural calamity

and a public health hazard, which originates from natural

systems including, anthropogenic as well as geological sour-

ces (Anawar et al., 2003; Ayoob and Gupta, 2006; Rafique et al.,

2009; Smedley et al., 2002).

Inorganic As is considered to be the major form of As in

groundwater, surface water, soil, and various foods (Tuzen

et al., 2010). Adverse health effects arising from the consump-

tion of drinking water, contaminated with As, is a serious

problem in several regions of the world, as a challenge for the

scientists (Smedleyetal., 2002) andmore recently fromPakistan

(Baig et al., 2009a; Farooqi et al., 2007; Nickson et al., 2005).

Inorganic arsenicals belong to group I carcinogens (IARC, 1987),

it causes cancers of the skin, lungs and bladder (Mandal and

Suzuki, 2002; Morales et al., 2000; Yoshida et al., 2004).

The literature studies show that the arsenic in water poses

the health hazards to humans, creates non-cancer effects such

ashyper- and hypo-pigmentation, keratosis, black foot disease,

hypertension, cardiovascular diseases anddiabetes (Abernathy

et al., 2003; Arun et al., 2001; Milton et al., 2004). Inorganic

Arsenic (iAs) species dissolved in drinking water are the most

significant forms of natural exposure. The fourmain species of

As occurs in water, inorganic forms such as arsenite ðH2AsO�3 Þ,

arsenate ðH2AsO�4 Þ, and organic forms (methyl arsenic acid

[CH3AsO(OH)2] and dimethyl arsenic acid [(CH3)2AsO(OH)].

Arsenite is 60 timesmore toxic than arsenate (Fazal et al., 2001).

Fluoride (F�) is an essential micronutrient for human

beings, serving to strengthen the apatite matrix of skeletal

tissues and teeth (Maithani et al., 1998). On the other hand,

high F� (>1.5 mg/L) results in dental and skeletal fluorosis;

renal and neuronal disorders along with myopathy (Ayoob

and Gupta, 2006). Fluorine is a lithophile element with atmo-

phile affinities, and occurs in many common rock-forming

minerals. Therefore, high F� concentrations in groundwater

are expected in areas where fluorine-bearing minerals are

abundant in the geologic substrate (Naseem et al., 2010; Shaji

et al., 2007; Tirumalesh et al., 2006). Endemic fluorosis

develops widely in many areas of the world, such as China

(Guo et al., 2006), India (Gupta et al., 2005), Mexico (Carrillo-

Rivera et al., 2002) and Africa (Gizaw, 1996). It was reported

previously that the groundwater of Thar desert, Pakistan was

highly contaminated with fluoride (Rafique et al., 2008).

The groundwater pollution by F� and As, due to coal

combustion, causes serious health diseases over large areas of

southern China (Finkelman et al., 2002), Inner Mongolia

(Smedley et al., 2002) and Pakistan (Farooqi et al., 2007).

The inorganic As compounds are much more hazardous

than organic As compounds. The speciation of As is very

important for the assessment of its toxicological and environ-

mental impacts. Moreover, it is necessary to develop sensitive

and precise methods to identify and quantify inorganic As

species in water. For the speciation of inorganic As, the

literature, solid phase extraction (Marahel et al., 2011), gold

nanoparticle loaded on activated carbon with bis(4-

methoxysalicylaldehyde)-1,2-phenylenediamine as sorbent

(Karimipour et al., 2012), cloud point extraction, co-

precipitation, ion exchange, and chromatography (Hirata and

Toshimitsu, 2005; Murata et al., 2005; Tuzen et al., 2009).

Among them, the cloud point extraction (CPE) technique was

used for the extraction of As species (As3þ and As5þ), based on

thephaseseparationofnon-ionic surfactants inaqueousmedia

(Bezerra et al., 2005; Pereira and Arruda, 2003). For the deter-

mination of total inorganic As (iAs), the enrichment on solid

phase (sorbent) from liquid phase (sample solution) is used

(Vieira et al., 2004; Zhang et al., 2005, 2007). These samples pre-

concentration methodologies are simple, low cost, environ-

mental friendly and provides high pre-concentration factor.

The application of different multivariate approaches

cluster analysis (CA) and principal components analysis (PCA)

for the interpretation of complex datamatrices, offers a better

understanding of water quality and ecological status of the

studied systems. The PCA and CA are also facilitate in the

identification of possible factors/sources that influence the

water systems and offer a valuable tool for reliable manage-

ment of water resources as well as rapid solutions on pollu-

tion problems (Reghunath et al., 2002; Zhang et al., 2011).

In present study a survey of groundwater at sub districts of

Tharparkar was carried out during 2011, to investigate the

level of total As, inorganic As species (As3þ, As5þ), F� and other

water quality parameters (temperature, pH, EC, TDS, salinity,

Naþ, Kþ, Ca2þ, Mg2þ, Cl�, SO2�4 , HCO�

3 , CO2�3 , Fe, Br�, NO�

2 NO�3

and PO3�4 ), to assess their potential relationship with F� and

different species of As. The iAs was determined by SPE using

TiO2 as the adsorbent, while As3þ by cloud point extraction

method used APDC as complexing reagent. The accuracy of

these methodologies has been validated by standard addition

method as reported in our previous work (Baig et al., 2009b).

In the present study, a large dataset obtained during 2011

was subjected to different multivariate statistical techniques

(PCA and CA) to extract information about the similarities or

dissimilarities between sampling sites and identification of

water quality variables responsible for groundwater contam-

ination. The analytical precision for the measurements of

cations (As [ 3þ & 5þ ], Ca2þ, Mg2þ, Naþ, Fe[II & III], and Kþ) andanions (CO2�

3 , HCO�3 , Cl

�, SO2�4 , NO�

3 , NO�2 , PO

3�4 and F�) were

indicated by the ionic balance error (IBE) was computed on the

basis of ions expressed inmeq/L. Sodium absorption ratio and

saturation index of water sample of each site were also

calculated to check the suitability of underground water for

irrigation purpose.

2. Materials and methods

2.1. Description of study area

The area under study were Chachro and Diplo sub districts

(North to south) of Tharparkar district, located in south-east

edge of the Sindh, Pakistan, and positioned between

24�27.9680e25�07.6880�N and 69�35.4630e70�13.0910�E (Fig. 1).

Fig. 1 e Sampling map of study area (Tharparkar’s district).

wat e r r e s e a r c h 4 7 ( 2 0 1 3 ) 1 0 0 5e1 0 2 0 1007

The entire area is covered by big and small sand dunes with

thorny bushes. The study area has an arid and tropical desert

climate, the temperature ranged from 9 �C to 48 �C with

200e300 mm average rainfall. Peoples of this area are mostly

rely on the groundwater for drinking as well as livestock

purpose. The underground water is available at the depth of

40e250 ft, which is obtained through a number of brackish to

saline open dug wells. The socioeconomic condition of Thari

people is poor, low literacy rate, (only 18.3%), including those

people who can read any newspaper or write a simple letter in

any language), limited health and other necessities for basic

life (Rafique et al., 2008). The land area of Tharparkar is spread

over about 19,638 km2 of which 6399 km2 and 4037 km2 area

covered with sub districts, Chachro and Diplo respectively.

The populations of both sub districts Chachro and Diplo are

514,526 and 232,816 respectively.

There aredifferent sources of drinkingwater inTharparkar,

of those 93.9% from wells, 2.26% of tube wells, 1.66% of Hand

pumps, 0.69% of pondwater and 1.47% other sources of water.

The Tharparkar district is very rich in minerals resources like

china clay, granite, coal and salts, so the groundwater is saline

in nature. There is no any fresh water supply for cultivation,

wat e r r e s e a r c h 4 7 ( 2 0 1 3 ) 1 0 0 5e1 0 2 01008

hence peoples depends on moon soon rain and underground

water (1998 District census report of Tharparkar).

In understudy areas it was reported in literature that geo-

electric; drilling and geophysical log data indicate four major

divisions of lithological sequences in the whole Thar Desert.

These zones are sand dune, sub-recent deposits, coal-bearing

formations of Paleocene, igneous and basement complex of

Precambrian age (Fassett and Durrani, 1994; Rafique et al.,

2008; Rehman et al., 1993; Zaigham and Ahmad, 1996).

2.2. Chemicals and glassware

Ultrapure water obtained from ELGA lab water system (Bucks,

UK) was used throughout the work. All chemicals and reagents

of EDTA, nitric acid, hydrogen peroxide, sulfuric acid, hydro-

chloric acid, sodium carbonate, potassium hydroxide, Sodium

hydroxide and sodium hydrogen carbonate were of analytical

grade, Merck (Darmstadt, Germany). The stock standard solu-

tion of As3þ at a concentration of 1000 mg/L was prepared by

dissolvingofAs2O3Merck (Darmstadt,Germany) in1MKOHand

adjusting the pH to 7.0 with 50% HCl. Working standard solu-

tions were prepared by stepwise diluting the stock solutions

just before use. While the working standard solutions for total

As were prepared by dilution of certified standard solution

(1000 mg/L), obtained from Fluka (Buchs, Switzerland) in 0.2M

HNO3. Triton X-114 (Sigma) was used as the non-ionic surfac-

tant. Ammonium pyrrolidinedithiocarbamate (Fluka) 0.1% (w/

v) was prepared by dissolving suitable amount of APDC in

ultrapurewater. Titanium (IV) dioxide (Merck, 99%, 0.5 mm)was

utilized as a sorbent. A 0.1% (w/v) of APDC solution was Stan-

dardsolutionof cations andanionswerepreparedbydilutionof

1000 ppm certified standard solutions (Fluka). The standard

reference materials SRM 1643e (water) was purchased from

National Institute of Standards and Technology (Gaithersburg,

MD, USA). The pH of the sample solution was adjusted with

0.1M HCl/0.1M NaOH. All the glassware were kept overnight in

5M HNO3, rinsed with deionized water before used.

2.3. Instruments

WIROWKA Laboratoryjna type WE-1, nr-6933 centrifuge

(speed range 0e6000 rpm, timer 0e60 min, 220/50 Hz, Mech-

anika Phecyzyjna, Poland) was used for centrifugation.

Mechanical shaker (Gallankamp, England) was used for

shaking. The measurement of electrical conductivity (EC) and

total dissolved solids (TDS) in water samples was analyzed by

using a conductometer (InoLab conduc. 720, Germany); pH

was measured by a pH meter (781-pH meter, Metrohm). A

global positioning system (iFinder GPS, Lowrance, Mexico)

was used for sampling locations. Metrohm ion analysis 861

Advanced Compact IC, Herisau, Switzerland with 833 IC

Liquid Handling Unit employed for anions analysis.

Graphite furnace Atomic absorption spectrometer of Perkin

Elmer, Model AAnalyst 700 USA, with a deuterium lamp back

corrector equipped with the graphite furnace HGA-400, pyro-

coated graphite tubes with integrated platform and auto

sampler 800 used for quantitative analysis of total As, inorganic

As and their species (Elci et al., 2008). The electrode discharge

lamp of As was run under the conditions suggested by the

manufacturer. The analytical wavelength was set at 193.7 nm.

The graphite furnace heating program was set for different

steps: drying temperature (�C)/ramp/hold(s) (140/15/15), ashing

temperature (�C)/ramp/hold(s) (1300/10/20), atomization

temperature (�C))/ramp/hold (2300/0/5), cleaning temp. (�C)/ramp/hold(s) (2600/1/3), using a modifier Mg(NO3)2 þ Pd(NO3)2.

Portions of both, standard or sample and modifier, were

transferred into auto-sampler cups, and 20 mL volume of 10 mL

standard or sample and 10 mLmodifier [5 mg Pdþ 3 mgMg(NO3)2]

was injected into the electrothermal graphite atomizer. Inte-

grated absorbance signals computed by the AA spectrometer

were employed throughout.

2.4. Sampling and pretreatment

Groundwater samples were collected on monthly basis, from

twelve (12) villages (n ¼ 10e20) of two sub-districts of Thar-

parkar as shown in Fig. 1, with the help of Global positioning

system (GPS) during 2011. All groundwater samples were

collected from >40 ft depth. The groundwater samples were

collected fromwell directly above the outlet afterwithdrawing

the samples several times from the water table with a stain-

less steel container tightened with a fiber rope. The collected

water samples were kept in well stopper polyethylene plastic

bottles previously soaked in 10% nitric acid for 24 h and rinsed

with ultrapure water (Gong et al., 2002).

The collected water samples were stored in an ice box, and

delivered to the laboratory on same day. Water samples from

each village/site were mixed into a washed plastic bucket to

madefive composite sampleof eachvillage andfiltered through

0.45 mm filter paper with the help of vacuum pump. The each

compositesampleweredivided into twoparts,ofwhichonesub

sample was acidified with 2e3 drops of conc. HNO3 for quanti-

tative analysis of cationswhile other bottlewas kept for arsenic

speciation, anions and other physicochemical parameters

determinations.All sampleswere storedat4 �Cuntil processing

and analysis (Clesceri et al., 1998; Kazi et al., 2009).

The analyses of As3þ and iAs were accomplished on

the same day to avoid risk of transformation of species as

reported elsewhere (Gong et al., 2002).

2.5. Analytical procedures

Different water quality parameters, their units, abbreviations

and methods of analysis applied in triplicate manner on each

composite samples of water are summarized in Table 1.

In the field, wemeasured water temperature, pH, electrical

conductivity (EC), total dissolved solids (TDS) and salinity

using thermometer, pH meter and conductivity meter,

respectively (Clesceri et al., 1998). Total hardness and Ca

hardness were measured by EDTA complexometric titration;

the indicators were Eriochrome Black T andMurexide at pH 10

and 12, respectively with an analytical error <2% (Eaton et al.,

1995). Carbonate ðCO2�3 Þ and bicarbonate ðHCO�

3 Þ ions

concentration were determined by titration with 0.02M HCl

using phenolphthalein andmethyl-orange indicators, showed

end points at pH 8.3 and 4.5 respectively.

The anions concentrations were determined through ion

chromatograph by measuring peak area of each with an error

<2% (Farooqi et al., 2007). For anions analysis, mobile phase of

1.7 mmol/L of Na2CO3, 1.8 mmol/L of NaHCO3 and standard

Table 1 e The water quality parameters associated withtheir abbreviations, units and analytical method.

Variables Abbreviations Units Analyticalmethod

pH pH pH unit pH-meter

Electrical

conductivity

EC mS/cm Conductivity meter

Salinity Salinity mg/L Conductivity meter

Total dissolved

solids

TDS mg/L Conductivity meter

Total-hardness T-hardness mg/L Titrimetric

Calcium

hardness

Ca-hardness mg/L Titrimetric

Magnesium

hardness

Mg-hardness mg/L Titrimetric

Fluoride F� mg/L Ion chromatography

Chloride Cl� mg/L Ion chromatography

Bromide Br� mg/L Ion chromatography

Phosphate PO3�4 mg/L Ion chromatography

Sulfate SO2�4 mg/L Ion chromatography

Nitrite NO�2 mg/L Ion chromatography

Nitrate NO�3 mg/L Ion chromatography

Carbonate CO2�3 mg/L Titrimetric

Bi-carbonate HCO�3 mg/L Titrimetric

Potassium Kþ mg/L FAAS

Sodium Naþ mg/L FAAS

Calcium Ca2þ mg/L FAAS

Magnesium Mg2þ mg/L FAAS

Iron Fe mg/L FAAS

Arsenic As mg/L GFAAS

wat e r r e s e a r c h 4 7 ( 2 0 1 3 ) 1 0 0 5e1 0 2 0 1009

mixed solutions of fluoride, chloride, bromide, nitrite, nitrate,

phosphate and sulfate at different concentration range

(0.25e16 mg/L) were prepared from certified stock standard

solutions. The concentration of Kþ, Naþ Ca2þ, Mg2þ and total

Fe were determined by Flame Atomic Absorption Spectro-

photometer (FAAS).

2.5.1. Determination of total As (tAs)For the determination of tAs, the groundwater (C-1eC-6 and

D-1eD-6) samples were diluted 25e50 times with deionized

water. For accuracy, a certified reference sample of water

(SRM 1643e) was treated as described in a previous work

(Arain et al., 2009; Baig et al., 2010).

2.5.2. Determination of total inorganic arsenic (iAs)Total iAs was determined as slurry by using TiO2 as the

adsorbent. The triplicates of each composite sample (20 ml) of

different origins were taken in flasks and complexing agent

TiO2 (10 mg) was added separately, and then the pH 2.0 was

adjusted with 0.5M HCl. The flasks were placed inside the

ultrasonic water bath and were subjected to ultrasonic energy

at 35 kHz for 10 min at room temperature, after that sample

solutions were centrifuged to separate the precipitates and

slurry was made by adding 5 ml of ultrapure water after being

subjected to an ultrasonic bath for 2 min and then the slurry

with the modifier was injected into a graphite tube by an

autosampler. The same procedure was applied for blank.

2.5.3. Determination of As3þ

The As3þ was determined by CPE, using a complexing reagent,

APDC and resulted complex was entrapped in Triton X-114.

The triplicates of each sample (20 ml) of different origins of

groundwater were placed in a beaker; pH was adjusted to 4.5

with 0.1M HCl, then added 0.01% (w/v) APDC and 0.12% (v/v)

Triton X-114 to the content of the tubes and heated in a ther-

mostatic water bath at 30 �C for 10 min. The mixture was

centrifuged at 4000 rpm for phase separation (5 min) and then

cooled in an ice bath for 10min to increase the viscosity of the

surfactant-rich phase. The supernatant aqueous phase was

carefully removed with a pipette. The 0.5 mL of 0.1M HNO3 in

methanol was added in surfactant rich phase to reduced the

viscosity, before ETAAS determination.

2.5.4. Estimation of As5þ

The concentration of As5þ could not be determined directly by

the above analytical procedure, but their concentrations were

given by the difference between iAs and As3þ.

2.6. Statistical analysis

All mathematical and statistical computations were made

using Statistica v5.5, XLSTAT-Pro v7.5.2 and Minitab 2002

v13.2 software. Multivariate statistical methods for classifi-

cation, modeling and interpretation of large datasets from

environmental monitoring programs allow the reduction of

the dimensionality of the data and the extraction of infor-

mation that will be helpful for the water quality assessment

(Liu et al., 2003).

Basic statistics and correlation calculations were carried

out in order to give initial information about the water quality

data. Unless otherwise indicated, the characteristics of the

cases were described as mean, minimum value, maximum

value, �95% confidence intervals of the mean value and

standard deviation (SD). In the present study multivariate

statistical methods, cluster analysis (CA) and principal

component analysis (PCA) were employed on the dataset of

fifty-six thousand values (26 parameters determined in five

composite samples of each 12 sampling sites for a period of 12

months in triplicates).

Concentration order among all physico-chemical parame-

ters, metals, halides and other anions differ greatly and the

statistical results should be highly biased by any parameter

with high concentration. Therefore standardization (z-scale)

wasmade on the resulted data of each parameters prior to the

statistical analysis (Simeonov et al., 2004). Standardization

tends to minimize the influence of difference on variance of

variables and eliminates the influence of different units of

measurements and renders the data dimensionless.

2.7. Analytical figure of merit

For quality control, analytical blanks and certified standard

solutions of all elements were prepared and analyzed using

the same procedures and reagents. The limits of detection

(LOD) was calculated as under, LOD (3 � s/m), where “s” is the

standard deviation of 10 measurements of the blank and “m”

is the slope of the calibration graph obtained for each case, the

LODs; 164.3, 69.2, 14.0, 2.46 and 5.52 mg/L for Ca2þ, Fe, Kþ, Mg2þ

and Naþ respectively.

For total and arsenic species, calibration graph obtained

from the quantification limit up to 20 mg/L of As. The LOD

wat e r r e s e a r c h 4 7 ( 2 0 1 3 ) 1 0 0 5e1 0 2 01010

values were 0.05 and 0.12 mg/L for As3þ and total iAs respec-

tively. The accuracy of methodologies was performed in

replicate three sub-samples of an underground water sample

by spiking standard solutions of each species at three

concentration levels, as shown in Table 2.

For validation of result, the measured TDS to calculated

TDS ratio and ionic balances were calculated. TDS test

provides a qualitative measure of the amount of dissolved

ions; it increases as the amounts of salts and other dissolved

solids increase in the water. The average ratio of measured

TDS to calculated TDS was found in all water samples, ranged

(1.00e1.07). For the validation of ions, ionic balances were

calculated (Lopez et al., 1999), observed in the range of

�1.98e2.37% respectively with no outliers was established,

the mean balance was 0.53%.

3. Results

The mean, standard deviation, minimum and maximum

values (range) of each parameter are shown in Table 3. To

evaluate the correlations between the levels of variables, the

Pearson correlation coefficients (r) were calculated. The

analysis of the collected samples indicated that most of the

variables were significantly deviate from regulated standard

values of WHO, for drinking water. The pH values fluctuated

between 7.5 and 10.0 in groundwater samples, which were

slightly above the WHO regulated values for drinking water.

TDS and EC in all groundwater samples were found in the

range of 937e7690 mg/L and 1.053e9.16 mS/cm respectively.

The high values of EC were attributed to the high salinity

(300e5200 mg/L) and soluble electrolytes in underground

water samples (Kazi et al., 2009). The alkalinity was found in

Table 2 e a) Analytical results of standard referencematerial, SRM 1643e (water), b) standard additionmethod/recovery for As3D and total iAs in a groundwatersample (D2).

a

SRM 1643e Certifiedvalues

Measuredvalues

% recovery

Na 20,740 � 260 20,520 � 278 98.9

K 2034 � 29 2010 � 42.1 98.8

Ca 32,300 � 1100 31,950 � 1170 98.9

Mg 8037 � 98 7970 � 102 99.2

Fe 98.1 � 1.4 97.2 � 2.51 99.1

tAs 60.45 � 0.72 59.5 � 1.88 98.4

b

Species Addedconc. (mg/l)

Mean � Std(mg/l)

% recovery

As3þ 0.00 29.0 � 2.4 e

5.0 33.6 � 2.79 98.8

10 38.3 � 3.42 98.2

20.0 48.6 � 2.95 99.2

iAs 0.00 89.8 � 2.56 e

5.0 93.7 � 6.18 98.8

10.0 97.9 � 8.05 98.1

20.0 107.9 � 7.72 98.3

the range of 275e1450 mg/L in groundwater samples, due to

the presence of CO2�3 and HCO�

3 . In groundwater, the

concentrations of Naþ, Kþ, Ca2þMg2þ and Fewere found in the

range of 166e2180, 8.16e22.3, 26.9e482, 48.9e207 and

0.109e0.327 mg/L respectively. The levels of Fe was within the

permissible limit of WHO.

The concentrations of F� was found in the range of

1.27e43 mg/L, while t-As, iAs, As(III) and As (V) were observed

in the range of, 0.117e2.58, 0.112e2.48, 0.040e0.880 and

0.103e2.01 mg/L respectively. The range of SO2�4 was observed

in groundwater samples as 73.7e728 mg/L, while Cl� ranged

from 28.7 to 2570 mg/L. The NO�2 , NO�

3 and PO3�4 in ground-

water were observed in the range of 12.6e20.9, 58.7e1310 and

47.1e55.9 mg/L respectively.

3.1. Sodium absorption ratio (SAR)

The sodium hazard is expressed in terms of sodium absorp-

tion ratio (SAR). The formula for calculating sodium adsorp-

tion ratio is:

SAR ¼ �Naþ�����Ca2þ�þ �

Mg2þ���2�1=2

The calculated values of SAR in sub district Chachro was

observed in the range of 11.0e27.4, with a mean value of 15.4,

which indicated very high Naþ and low Ca2þ concentrations in

the groundwater of this area, while in Diplo sub district SAR

values was observed in the range of 3.9e14.9 with a mean

value of 6.23.

3.2. Saturation index

The saturation index of different salts in the groundwater

samples were calculated using PHREEQCI version 2 (Parkhurst

and Appelo, 1999) and are shown in Fig. 2. The intensity of

soluble minerals is expressed as saturation index. The satura-

tion indices for fluorite and calcite in groundwater samples

collected within the study area were calculated and plotted in

Fig. 2a, which shows that the 42% of the total samples were

oversaturated (>2 values), while 58.3% were saturated

(0.68e1.58) with respect to calcite. The 16.7% sampling sites

were unsaturated with respect to fluorite whereas, majority of

sampleshavebeensaturated (0.48e1.86),whileC4hadvalue>2.

4. Discussion

4.1. Physicochemical parameters

The resulted data indicated the wide variations in the levels of

all physicochemical parameters including As and F� contam-

inations in groundwater, may be due to the complex geo-

chemical involvement factors in understudy areas. The other

water quality parameters of understudy samples revealed that

thewater was hard consistent with the presence of high levels

of sulfate and chloride (Table 3). The EC and TDS are signifi-

cantly correlated with cations and anions (Ca2þ, Kþ, Naþ, Cl�,NO�

3 and SO2�4 ) in groundwater samples, which might be the

result of ion exchange in the aquifer (Baig et al., 2009a; Lopez

able 3 e Range, mean and standard deviation (Std.) of water quality parameters at different sites in sub districts Chachro a d Diplo of Tharparkar, during 2011.

arameter WHOlimits

C-1 C-2 C-3 C-4 C-5 C-6 D-1 D-2 D-3 D-4 D-5 D-6

H 6.5e9 Range 7.94e9.23 7.22e8.19 8.06e9.45 9.74e10.4 8.73e9.98 7.01e7.96 7.87e8.91 7.99e9.14 7 5e9.07 8.11e9.00 8.02e8.92 8.22e8.58

Mean 8.31 7.62 8.74 10.05 9.36 7.50 8.26 8.33 8 6 8.51 8.47 8.37

Std 0.520 0.424 0.557 0.228 0.496 0.386 0.389 0.464 0 84 0.326 0.325 0.142

C mS/cm 0.250 Range 6.53e7.65 4.95e5.39 8.96e9.45 6.20e6.59 3.25e3.56 8.55e8.73 1.77e1.92 1.29e1.52 4 1e4.25 2.03e2.23 0.95e1.14 1.66e1.80

Mean 7.29 5.19 9.16 6.38 3.45 8.61 1.837 1.392 4 3 2.08 1.053 1.719

Std 0.441 0.161 0.191 0.141 0.129 0.076 0.057 0.085 0 00 0.087 0.093 0.060

alinity mg/L e Range 3600e4200 2600e2800 5100e5400 3400e3600 1400e1600 4700e4900 800e800 500e500 2 00e2200 800e1000 300e300 700e700

Mean 4000 2700 5200 3500 1500 4800 800 500 2 00 900 300 700

Std 234 70.7 122 70.7 70.7 70.71 0.00 0.00 7 .7 70.7 0.00 0.00

DS mg/L 1000 Range 5030e5570 4190e4400 7590e7840 5840e6040 3150e3290 5740e5820 1400e1470 1010e1120 3 50e3360 1870e1960 890e980 1350e1410

Mean 5390 4310 7690 5930 3240 5770 1430 1060 3 00 1890 937 1370

Std 210 74.8 97.6 70.0 57.9 32.0 25.6 38.3 4 .3 38.9 42.1 26.9

otal hardness

mg/L

500 Range 621e865 793e1290 1440e2190 90.0e206 102e277 1770e2480 787e1160 734e1150 1 30e1830 1030e1390 430e590 802e1200

Mean 705 1020 1750 150 155 2130 960 960 1 35 1220 500 1000

Std 98.9 204 286 41.2 46.9 267 148 150 2 9 175 65.5 171

a-hardness

mg/L

100 Range 380e412 612e655 688e781 31e68 101e127 722e766 613e681 690e755 7 2e832 735e789 326e382 666e728

Mean 400 635 720 45 110 735 630 720 8 0 760 360 700

Std 12.4 16.1 36.9 15.2 10.4 17.9 28.7 25.0 1 .7 23.7 21.1 25.3

g-hardness

mg/L

50 Range 209e457 163e640 748e1460 56e175 25e126 1050e1750 170e475 173e328 4 5e1030 254e657 58.0e264 117e537

Mean 305 385 1030 105 45 1400 330 240 6 5 465 140 300

Std 99.9 191 288 44.2 55.9 259 128 59.2 2 1 188 78.5 180� mg/L 1.5 Range 18.8e20.7 24.1e24.7 22.4e25.8 25.7e60.5 28.8e30.8 4e78e7.83 11.5e19.7 13.6e19.8 1 .1e18.7 14.7e17.7 0.966e1.91 2.45e10.6

Mean 19.75 24.42 24.09 43.11 29.82 6.45 15.61 16.7 1 .4 16.3 1.27 6.52

Std 0.831 0.242 1.17 15.9 0.878 1.34 2.90 2.47 2 9 1.11 0.398 2.89

l� mg/L 250 Range 1550e1970 1370e1740 1990e2480 703e1030 151e252 2220e2910 204e275 81.0e134 1 90e1500 246e328 8.01e49.4 33.8e78.1

Mean 1740 1550 2240 867 201 2570 239 108 1 90 287 28.7 55.9

Std 198 155 181 127 43.2 244 30.6 19.6 8 .1 34.8 15.3 22.0

r� mg/L e Range 20.3e23.3 20.3e24.2 20.3e23.9 285e345 77.6e90.2 20.3e22.3 0.0e0.0 0.0e0.0 8 2e9.04 8.66e8.82 0e3.09 2.16e4.01

Mean 21.79 22.24 22.11 320.21 83.85 21.27 0.0 0.0 8 3 8.74 1.55 3.09

Std 1.21 1.76 1.53 28.0 6.20 0.813 0.0 0.0 0 98 0.064 1.29 0.795

O�2 mg/L 0.50 (EU) Range 0.0e0.0 0.0e0.0 0.0e0.0 0.0e0.0 0.0e0.0 0.0e0.0 20.3e21.5 16.8e19.9 1 .3e13.0 12.2e13.0 17.5e18.4 0.0e0.0

Mean 0.0 0.0 0.0 0.0 0.0 0.0 20.9 18.38 1 .65 12.65 17.96 0.0

Std 0.0 0.0 0.0 0.0 0.0 0.0 0.554 1.50 0 58 0.355 0.369 0.0

O�3 mg/L 50 Range 151e202 314e399 1140e1470 680e943 454e660 187e264 53.7e63.8 17.3e183 5 .8e66.9 366e430 198e232 337e393

Mean 177 357 1310 811 557 225 58.7 78.7 6 .9 398 215 365

Std 19.6 32.6 122 101 81.6 32.8 3.90 68.5 3 4 30.0 13.8 23.5

O3�4 mg/L e Range 0.0e0.0 0.0e0.0 0.0e0.0 0.0e0.0 0.0e0.0 0.0e0.0 0.0e0.0 0.0e0.0 0 e0.0 45.0e52.3 37.9e56.3 44.7e67.1

Mean 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 48.62 47.12 55.92

Std 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 2.92 7.96 10.32

O2�4 mg/L 500 Range 398e409 412e440 692e765 686e692 404e431 613e636 109e158 144e170 2 7e252 161e221 35.0e112 147e185

Mean 403 426 728 689 417 624 133 157 2 4 191 73.7 166

Std 4.46 11.7 27.7 2.73 9.97 8.65 18.9 11.0 1 .2 25.6 31.8 15.1

(continued on next page)

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1011

T

P

p

E

S

T

T

C

M

F

C

B

N

N

P

S

n

.7

.4

.4

.0

.1

.1

0

1

0

2

3

5

2

4

3

8

1

9

0

2

5

2

5

.3

2

3

2

.8

.9

.0

2

2

.3

8

2

.6

.0

.0

.0

1

3

3

Table 3 e (continued )

Parameter WHOlimits

C-1 C-2 C-3 C-4 C-5 C-6 D-1 D-2 D-3 D-4 D-5 D-6

CO2�3 mg/L e Range 423e481 0.0e0.0 209e306 301e384 231e291 0.0e0.0 0.0e0.0 72e126 7e112 79e152 64e132 84e108

Mean 450 0.0 250 350 250 0.0 0.0 100 00 100 100 100

Std 27.3 0.0 37.6 31.2 23.7 0.0 0.0 23.6 1.6 30.2 25.0 9.77

HCO�3 mg/L e Range 525e579 330e398 456e507 1060e1150 661e734 291e318 477e527 183e216 33e305 222e280 146e207 182e221

Mean 550 350 475 1100 700 300 500 200 75 250 175 200

Std 22.5 27.7 21.8 37.0 27.6 10.6 21.8 15.4 7.3 24.7 23.4 14.5

Naþ mg/L 200 Range 924e1500 887e1360 1690e2440 943e1380 585e866 1300e1800 218e310 145e223 08e1250 234e328 133e194 211e291

Mean 1230 1110 2180 1150 701 1480 248 179 24 271 166 249

Std 242 211 288 173 103 211 36.3 30.5 18 40.2 25.0 32.9

Kþ mg/L 12 Range 14.3e22.7 13.9e20.0 20.2e26.3 9.14e15.6 12.9e15.8 15.2e23.6 11.9e27.4 9.33e13.6 .44e14.3 6.64e13.3 6.26e11.2 7.65e12.4

Mean 18.8 16.8 22.3 14.0 14.6 18.0 18.3 11.8 1.2 11.0 8.20 10.6

Std 3.16 2.32 2.43 2.73 1.16 3.28 6.57 1.96 .23 3.06 1.88 1.86

Ca2þ mg/L 100 Range 422e538 118e171 185e294 313e487 161e172 206e319 32.4e44.3 54.1e63.37 8.9e145 88.3e169 46.9e57.3 23.7e29.6

Mean 482 153 233 406 167 265 39.2 58.1 13 130 51.1 26.9

Std 44.5 20.5 39.1 62.3 3.73 40.0 4.32 3.37 3.7 29.7 3.96 2.12

Mg2þ mg/L 50 Range 107e141 127e174 129.e168 153e213 81.3e90.6 172e243 65.3e108 55.2e68.4 2.1e149 107e146 42.6e58.9 64.3e91.8

Mean 123 152 148 173 85.8 207 87.3 60.9 09 124 48.9 78.7

Std 13.9 17.8 15.2 24.3 4.10 25.1 20.0 4.96 8.7 15.0 6.39 9.97

Fe (II & III) mg/L 0.2 (EU) Range 0.097e0.132 0.143e0.229 0.102e0.147 0.128e0.188 0.166e0.231 0.291e0.378 0.108e0.154 0.112e0.141 .269e0.356 0.235e0.291 0.092e0.123 0.104e0.144

Mean 0.114 0.196 0.130 0.159 0.192 0.328 0.134 0.126 .303 0.258 0.109 0.122

Std 0.0135 0.0336 0.0177 0.0228 0.0249 0.0348 0.0186 0.0107 .0329 0.0289 0.0112 0.0146

Total-As mg/L 0.01 Range 1.26e2.85 0.948e2.87 1.26e3.36 1.98e4.33 0.826e1.86 1.54e2.46 0.006e0.329 0.094e0.578 .072e3.27 0.065e1.55 0.059e0.417 0.087e0.594

Mean 2.09 1.56 2.15 2.58 1.32 1.90 0.117 0.233 .875 0.467 0.158 0.233

Std 0.567 0.771 0.850 1.01 0.440 0.357 0.132 0.201 .38 0.624 0.146 0.210

Inorganic-As

mg/L

Range 1.19e2.77 0.715e2.09 1.20e3.26 1.19e4.10 0.785e1.59 1.44e2.38 0.006e0.312 0.0898e0.419 .068e2.46 0.062e1.47 0.056e0.304 0.083e0.476

Mean 2.00 1.39 2.07 2.48 1.26 1.82 0.112 0.224 .840 0.448 0.152 0.224

Std 0.771 0.653 1.06 1.18 0.430 0.493 0.145 0.174 .06 0.598 0.106 0.162

As-(III) mg/L Range 0.386e01.07 0.327e0.682 0.389e1.26 0.609e1.39 0.254e0.612 0.472e0.921 0.002e0.101 0.029e0.177 .027e0.936 0.020e0.475 0.018e0.130 0.027e0.172

Mean 0.712 0.493 0.735 0.880 0.449 0.647 0.040 0.079 .297 0.159 0.054 0.079

Std 0.283 0.171 0.386 0.311 0.159 0.188 0.0510 0.0650 .389 0.188 0.0457 0.0652

As-(V) mg/L Range 0.816e1.67 0.692e1.91 0.822e1.97 1.29e2.65 0.537e0.957 0.998e1.44 0.004e0.193 0.061e0.351 .047e2.40 0.042e0.965 0.038e0.263 0.056e0.360

Mean 1.27 1.21 1.43 1.75 0.760 1.23 0.103 0.208 .12 0.498 0.149 0.210

Std 0.307 0.546 0.435 0.528 0.162 0.186 0.079 0.130 .05 0.412 0.101 0.136

Temperature �C Range 24.6e25.8 27.3e28.8 29.3e31.1 21.9e23.3 22.5e23.8 31.9e34.0 25.5e26.6 25.4e27.1 9.1e30.4 27.7e28.7 23.2e25.0 26.4e28.2

Mean 25.1 27.9 30.2 22.7 23.0 32.8 26.1 26.2 9.5 28.3 24.1 27.4

Std 0.436 0.600 0.671 0.570 0.524 0.875 0.430 0.612 .543 0.400 0.831 0.758

SAR Mean 12.9 15.2 27.4 12.0 11.0 16.5 5.04 3.92 4.9 4.08 3.99 5.47

S.I of calcite Mean 2.15 0.68 2.05 2.95 2.43 0.73 0.99 1.04 .47 1.55 1.1 0.76

S.I of gypsum Mean �0.82 �1.17 �0.940 �0.820 �1.17 0.900 �1.99 �1.68 1.50 �1.41 �1.99 �2.00

S.I of dolomite Mean 4.07 1.72 4.33 5.94 4.96 1.77 2.68 2.46 .21 3.47 2.52 2.35

S.I of fluorite Mean 1.86 1.58 1.58 2.30 1.81 0.480 0.85 1.14 .09 1.30 �1.07 �0.050

Cal TDS/mean

TDS

Mean 1.03 1.03 1.01 1.00 1.01 1.01 1.05 1.07 .01 1.02 1.00 1.04

Ion balance error Mean 1.30 2.37 0.860 �1.75 1.38 0.210 1.08 1.80 .790 0.130 0.210 �1.98

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8

1

1

2

2

2

7

9

2

8

1

2

8

1

2

6

1

3

0

0

0

0

0

1

0

0

1

0

0

0

0

1

1

2

2

0

1

1

�3

1

1

0

Fig. 2 e Relationshipsbetweenvariouschemical componentsof undergroundwater samples. (a) Fluorite saturation indexand

calcite saturation index, (b) Dolomite saturation index and calcite saturation index, (c) Calcite saturation index and gypsum

saturation index, (d) Ca2D concentrationandcalcite saturation index, (e)Mg2D concentrationanddolomite saturation index, (f)

Gypsum saturation index and Ca2D, (g) Gypsum saturation index and SO42- and (h) Fluorite saturation index (SIf) and FL.

wat e r r e s e a r c h 4 7 ( 2 0 1 3 ) 1 0 0 5e1 0 2 0 1013

et al., 1999). The studied ground waters are usually basic in

nature, have high EC due to elevated levels of TDS, reflecting

moderate mineral dissolution. The intensity of soluble

minerals is expressed as saturation index. In understudy

Fig. 3 e Dendrogram showing clustering of different sites of gro

other physicochemical parameters.

groundwater samples, the saturation index (SI) of calcite has

shown significant correlation with SI of dolomite and gypsum

(Fig. 2b andc). Thepositive correlationof SI of calcitewithCa2þ,SI of dolomite with Mg2þ, while Ca2þ and SO2�

4 corresponds to

undwater according to distribution of As species, FL and

Table 4 e Factors loadings of experimental variables (26)on significant principal components for groundwater oftwo sub districts of Tharparkar.

Parameters F1 F2 F3 F4

pH 0.145 �0.880 0.087 0.242

TDS 0.991 0.020 �0.083 0.027

EC 0.976 0.177 �0.083 �0.028

Salinity 0.972 0.185 �0.090 �0.024

CO3 0.477 �0.636 �0.378 0.032

HCO3 0.559 �0.761 0.153 �0.128

T-Hard 0.589 0.789 �0.034 0.091

Ca-Hard 0.631 0.684 �0.239 0.061

Mg-Hard 0.519 0.792 0.090 0.102

F 0.543 �0.700 0.179 �0.133

Cl 0.852 0.478 �0.014 �0.113

Br 0.452 �0.759 0.381 0.136

NO2 �0.750 0.092 0.112 �0.324

NO3 0.607 �0.270 �0.271 0.481

PO4 �0.586 0.070 �0.137 0.729

SO4 0.963 �0.087 0.043 0.105

As-total 0.970 �0.197 0.018 �0.004

As-iorganic 0.971 �0.204 0.015 0.002

As-III 0.971 �0.204 0.015 0.002

As-V 0.923 �0.201 0.212 0.031

Na 0.948 0.178 �0.146 0.015

K 0.730 0.186 �0.334 �0.386

Ca 0.818 �0.293 �0.066 �0.108

Mg 0.855 0.220 0.357 0.080

Fe 0.236 0.501 0.752 0.085

Temperature in C 0.276 0.909 0.133 0.129

Eigenvalue 14.52 6.37 1.44 1.22

Variability (%) 55.9 24.5 5.54 4.70

Cumulative % 55.9 80.4 85.9 90.6

wat e r r e s e a r c h 4 7 ( 2 0 1 3 ) 1 0 0 5e1 0 2 01014

SI of gypsum (Fig. 2d, e, f and g), indicated that, theseminerals

are in a state of super saturation in groundwater.

It was observed that the underground water samples of

Chachro have high levels of Naþ, which may reflect both the

dissolution of lithogenic Naþ and the exchange of dissolved

Ca2þ with Naþ by clay minerals in the aquifer. This assump-

tion is also signified from high Naþ/Ca2þ ratios (5.32), which

show ion exchange between Naþ absorbed on the surface of

clay minerals and Ca2þ in the groundwater (Guo and Wang,

2005).

4.2. Cluster analysis

In cluster analysis the objects are grouped such that the

similar objects fall into the same class (Danielsson et al., 1999),

levels of similarity at which observations are merged are used

to construct a dendogram (Chen et al., 2007). The resulted

dendogram (Fig. 3) grouped all the twelve sampling sites into

three statistically significant clusters. The dataset was treated

(after data scaling by z-transformation) by theWard’s method

of linkage with squared Euclidean distance as measure of

similarity. The sampling sites D-1, D-2, D-4, D-5 and D-6made

one group as cluster 1, which corresponds to 41.7% of all the

sample sites, The underground water samples of sites in this

cluster contained t-As and F� in the concentration range of

0.117e0.467 mg/L and 1.27e16.7 mg/L respectively. While due

to mutual dissimilarity among other sampling origins of

ground water made of cluster 2, which were corresponds to

33.3%, involved C-1, C-3, C-4 and C-6 sites contains t-As and F�

concentration in the range of 1.90e2.58 mg/L and

6.45e43.11 mg/L, respectively. The cluster 3, involved C-2, C-5

and D-3 sites corresponds to 25% of total sampling sites,

contains T-As and F� in concentration range of 0.875e1.56mg/

L and 15.4e29.8 mg/L, respectively. The underground water

sample of twelve sites were grouped into clusters 1, 2 and 3,

classified as low, high andmedium polluted areas with As and

F� levels, respectively.

4.3. Principal component analysis

The principal component analysis (PCA) is a powerful pattern

recognition technique that attempts to explain the variance of

a large dataset of intercorrelated variables with a smaller set

of independent variables (Simeonov et al., 2003). PCA was

employed on our dataset to compare the compositional

patterns between the examinedwater systems and to identify

the factors that influence each one. Four components of PCA

analysis showed 90.6% of the variance on the resulted data of

underground water samples of Tharparkar sub districts as

shown in Table 4. The first component (F1) accounted for over

55.8% of the total variance in the dataset of groundwater; the

physical parameters, major cations, anions, Fe and As species

were loaded, which may be indicated geological effects. From

a macroscopic point of view all the physico-chemical

parameters except few, behave similarly, i.e. high concentra-

tion of major elements as well as As species in the main body

of all groundwater samples. The second component (F2),

explaining 24.5% of the total variance, has strong positive

loadings with T-Hard, Ca-Hard, Mg-Hard, iron and tempera-

ture, indicates the climatic effect. The third component (F3) of

PCA shows 5.5% of the total variation has positive loadingwith

Mg2þ, Fe, and Br�. While fourth component (F4) of PCA shows

only 4.7% of the total variation has positive loading with NO�3

and PO3�4 , may due to agriculture or nutrient effect (Khan,

2011; Simeonov et al., 2003; Zhang et al., 2011).

The above observation is clearly shown in Fig. 4a, which

shows the characteristics of samples and helps to understand

their spatial distribution. It is evident that samples distributed

in the upper right quadrant are more enriched with TDS, EC,

Salinity, Naþ, Mg2þ, Kþ, Fe, Cl�, Mg-Hardness, Ca-Hardness, T-

Hardness and temperature while those in the lower right

quadrant are enriched with As species, Ca2þ, NO�3 , Br

�, F�,SO2�

4 , CO2�3 and HCO�

3 and pH. The samples distributed in the

other two quadrants (upper and lower left) are enriched with,

NO�2 and PO3�

4 to a lesser extent.

The scores plot (F1 and F2) for the groundwater samples

(Fig. 5b) shows high distribution of As species, F� and other

water quality parameters in groundwater samples of Chachro

sub-district, which are mostly appeared in the right quad-

rants, while the all sampling sites of Diplo sub district are

appeared in the left quadrant. It means high variations of

physicochemical parameters were occurs in Chachro sub

district, due to leaching effect while in Diplo sub district

variation were due to climatic effect.

The high level of As species in groundwater samples

introduced by geothermal, geohydrological and geochemical

factors (Singh and Ma, 2006; Smedley et al., 2002). The agri-

cultural/industrial pollution as a source of As is not counted in

Fig. 4 e Plots of PCA (a) scores for distribution of As species and water quality parameters in sub-districts of Tharparkar and

(b) scores for combined dataset of groundwater samples.

wat e r r e s e a r c h 4 7 ( 2 0 1 3 ) 1 0 0 5e1 0 2 0 1015

present study, as there is no available data on the use of

arsenical pesticides or industrial chemicals in understudy

areas.

4.4. Total As and inorganic As species in undergroundwater

The concentration of total As distributed in groundwater

samples of sub districts of Tharparkar, Pakistan varied from

0.117 to 2.58 mg/L. The concentration of As are 10e250 times

higher than permissible limits of WHO (0.010 mg/L). The

concentration of iAs was found to be 4e6% lower than the

total As (Table 3), indicating the lesser availability of organic

As in groundwater (Thirunavukkarasu et al., 2002).

For the determination of inorganic arsenic (iAs), the inor-

ganic metal oxide, TiO2 had been applied as solid sorbent, due

to its high surface area, while for the determination of As3þ

cloud point extractionmethod was applied (Zhang et al., 2004;

Fig. 5 e Standard unit of chemical concentrations of FL and

As species in groundwater of the sub districts Chachro and

Diplo of Tharparkar district. The standard units is defined

as z [ (x e u)/S, where x is the raw concentrated data, u is

the mean values and S is the standard deviation.

Baig et al., 2009b), which offer a simple, rapid, sensitive,

inexpensive and non-polluting alternative to other

separation/pre-concentration techniques and analytical

characteristics of the this method were given in Table 5. For

the optimization of CPE, five factors were selected to be

examined: amount of surfactant, mass of complexing agent,

pH, and equilibrium temperature and time. The optimization

of different variables for the determination of As3þ and total

iAs were reported in our previous work (Baig et al., 2009b).

To evaluate the selectivity of the proposed methods for

determination of trace levels of As3þ and iAs, the effect of

typical potential interfering ions was investigated. About 1 mg

of As model solutions (100 mL) containing matrix ions were

used in this study. The metallic ions, Naþ and Cl (1000 mg),

Ca2þ, Mg2þ, Kþ, SO2�4 and PO3�

4 (100 mg of each), Fe3þ (1.0 mg)

were added to 1000 mL of sub-sample of groundwater and

subjected to corresponding methods. An ion was considered

as interferent, when it caused a variation in the absorbance of

the analyte greater than �5%. The tolerance limits of various

foreign ionswerewithin 95% confidence limit. It was observed

that excess amounts of common cations and anions do not

interfere on the determination of trace quantities of As3þ and

iAs while Fe has negative effect <5%. Knowledge of the

speciation of As in natural water is important because the

bioavailability, physiological and toxicological effects of As

depend on its chemical form. Thus, it is most decisive to

determine As species rather than the total amount of As in

water samples (Ahmad et al., 2004; Pei and Rui, 2007; Prasenjit

et al., 2007; Sharestha, 2002).

As shown in Table 6, total As and its species have positive

correlation with all physicochemical parameters except NO�2

and PO3�4 . It was observed that in all groundwater samples, the

contamination of As5þ was prominent as compared to As3þ

(Table 3). It was reported that high levels of As5þ in contami-

nated groundwater is due to oxidizing environment, which

were characterized by high concentrations of HCO3

(>500 mgL�), SO2�4 (>250 mgL�), and pH > 7.5 (Maity et al.,

2004; Smedley et al., 2002). Such processes are considered to

Table 5 e Analytical characteristics of the proposed method.

Element condition Concentrationrange (mg/L)

Slope Intercept R2 R.S.D LOD (mg/L)

As without

preconcentration

150e2500 4.26 � 10�3 �0.009 0.9914 1.27 26.0

As with

preconcentration

10.0e75 0.291 þ0.008 0.9989 1.85 0.31

wat e r r e s e a r c h 4 7 ( 2 0 1 3 ) 1 0 0 5e1 0 2 01016

have been responsible for the release of As in oxidizing

quaternary sedimentary aquifers (Singh, 2006; Smedley et al.,

2002). The source of the inorganic As species might be due to

the pyretic material or black shale occurring in the underlying

geological strata (Thornton and Farago, 1997). The SI results

may be attributed to extensive water logging of study area and

is promoting contamination of As in the studied groundwater

(Ito et al., 2001).

The climate of Thar region is relatively arid. This aridity

can lead to evaporation; enhance the concentration of arsenic

in shallow groundwater. Evaporative concentration is

a contributing factor leading to high arsenic in addition to

elevated dissolved solids contents in underground water of

both sub districts of Tharparkar, particularly in some areas of

Chachro. The As species have high correlation with salinity

(r ¼ �0.906, p < 0.001).

4.5. F� in underground water

The associations of F� bymeans of correlation coefficient with

other physicochemical parameters are shown in Table 6. A

positive correlation between F� concentration and pH was

observed (r ¼ 0.694, p ¼ 0.012) which is consisted with other

study (Vasquez et al., 2006). This may be due to the similar

ionic radii of F� andOH�, which often substitute for each other

within minerals (Rafique et al., 2009). It was reported that clay

minerals are able to hold F� ions on their surfaces, but at high

pH, OH� ions can displace F� ions, which are then released to

groundwater (Rafique et al., 2009; Sreedevi et al., 2006). This

fact indicates that the undergroundwater samples of both sub

districts of Tharparkar have high levels of F� and pH

(7.5e10.05), these results are consisted with other study

carried out in India (Saxena and Ahmed, 2003).

The F� have strong positive correlation with HCO�3

(r ¼ 0.874, p < 0.001). Thus, an alkaline pH is favorable for F�

dissolution (Saxena and Ahmed, 2003). The same trend was

observed in other studies carried out in different parts of the

world (Gizaw, 1996; Rafique et al., 2008). The TDS have positive

correlationwith F� (r¼ 0.509, p¼ 0.091), It was observed that in

site D-5, the F� concentration was <1.5 mg/L which is asso-

ciatedwith lower value of TDS (937mg/L), while at C3 the high

contents of F� corresponds to TDS level of 5930 mg/L (Table 3).

The resulted data is consistedwith other study (Sreedevi et al.,

2006; Subba, 2003).

The saturation indices for fluorite and calcite in ground-

water samples were calculated (Parkhurst and Appelo, 1999)

and plotted in Fig. 2a. The saturation index of fluorite (SIf)

increases with increasing F� concentration, and reaches the

saturation state when the F� concentration is >40 ppm

(Fig. 2h). This indicated that the fluorite saturation in ground-

water samples might be due to the calcite undersaturation,

preventing it by reducing calcium activity and allowing more

fluorite to dissolve, thereby increasing the F�/Ca2þ ratio of

solution (Datta et al., 2000; McCaffrey and Willis, 2001). Hence

calcite and fluorite are the main minerals controlling the

aqueous geochemistry resulted into elevated levels of F� in the

groundwater samples of sub district Chachro and Diplo. This

situation of solubility control on thehigher concentration of F�

can be explained by the fact that F� in groundwater can be

increased as a result of precipitation of CaCO3 at high pH,

which removes Ca2þ from solution allowing more fluorite to

dissolve (Kundu et al., 2001).

The high levels of F� (>1.5mg/L) causes dental and skeletal

fluorosis and may harm to kidneys, nerves and muscles

(Ayoob and Gupta, 2006). Problem of dental and skeletal fluo-

rosis is common in the areas of crystalline basement rocks,

particularly those of granitic composition in different part of

the world (Edmunds and Smedley, 2005). The population of

Thar desert in the Sindh province of Pakistan are severely

suffering from dental and skeletal fluorosis, bone deforma-

tion, mainly due to F� toxicity (Rafique et al., 2009).

4.6. Overview of the arsenic and fluoride

Concentration order of arsenic and Fluoride in underground

water samples differ greatly and the statistical results should

be highly biased by any parameter with high or low concen-

tration. Therefore the data of arsenic species and F� were

transformed into standard unit (z) to compare the aspects of

the variation in water samples collected from different sites.

Fig. 5 indicates that As species and F� in groundwater samples

of sub district Chachro have similar behavior, while variation

in these parameters were occur in Diplo sub district. The As

and F� show low normalized values (<0) at all sites of sub

district Diplo except at D-3, where the As (V) level is higher

than normalized value (>0), while in Chachro sub district

most of the sampling sites contained high levels of As species

(>0 s), except at C-6 where only F� level is lower than

normalized value (Fig. 5). The levels of these parameters were

found to be very high (�2 s) at sampling site C-4 showing high

pollution at that site and very low pollution (��1) at sampling

sites, D-1 and D-5.

The concentrations of As species and F� are positively

correlated with each other (Table 6), however, both elements

are enriched in groundwater, suggesting the contribution of

a common source or pathway for both elements. It was re-

ported that the underground water pollution by F� and As,

causes serious health diseases over large areas of southern

China (An et al., 1997; Finkelman et al., 2002; Zheng et al., 1996)

and Inner Mongolia (Wang et al., 1999; Smedley et al., 2002),

due to coal mining and combustion, although F� does not

coexist with As in polluted groundwater in most other areas.

Table 6 e Linear Pearson correlation coefficient matrix for different physicochemical parameters with FL and As species.

pH TDS EC Salinity CO3 HCO3 T-hard Ca-hard Mg-hard F Cl Br NO2 NO3 PO4 SO4 tAs iAs As-III As-V Na K Ca Mg Fe

TDS 0.145

0.653

EC �0.023 0.978

0.944 0.000

Salinity �0.029 0.977 0.999

0.929 0.000 0.000

CO3 0.644 0.482 0.401 0.394

0.024 0.112 0.197 0.204

HCO3 0.756 0.521 0.401 0.392 0.644

0.004 0.083 0.196 0.207 0.024

T-hard �0.546 0.606 0.716 0.722 �0.187 �0.275

0.066 0.037 0.009 0.008 0.560 0.387

Ca-hard �0.541 0.649 0.743 0.742 0.014 �0.237 0.919

0.069 0.022 0.006 0.006 0.966 0.459 0.000

Mg-hard-0.508 0.535 0.647 0.656 �0.292 �0.277 0.972 0.802

0.092 0.073 0.023 0.020 0.356 0.384 0.000 0.002

F 0.694 0.509 0.359 0.347 0.563 0.874 �0.254 �0.156 �0.293

0.012 0.091 0.252 0.270 0.056 0.000 0.426 0.628 0.356

Cl �0.337 0.860 0.931 0.932 0.132 0.100 0.858 0.857 0.793 0.104

0.284 0.000 0.000 0.000 0.683 0.757 0.000 0.000 0.002 0.747

Br 0.781 0.406 0.281 0.278 0.512 0.884 �0.331 �0.364 �0.287 0.787 0.004

0.003 0.190 0.376 0.382 0.089 0.000 0.293 0.245 0.365 0.002 0.991

NO2 �0.135 �0.724 �0.703 �0.687 �0.445 �0.424 �0.349 �0.484 �0.241 �0.413 �0.549 �0.376

0.675 0.008 0.011 0.014 0.147 0.170 0.267 0.111 0.450 0.182 0.065 0.228

NO3 0.514 0.660 0.530 0.532 0.430 0.478 0.224 0.256 0.188 0.544 0.296 0.442 �0.549

0.088 0.020 0.076 0.075 0.163 0.116 0.484 0.421 0.559 0.068 0.350 0.151 0.065

PO4 �0.046 �0.561 �0.562 �0.552 �0.208 �0.480 �0.229 �0.221 �0.217 �0.544 �0.534 �0.255 0.189 �0.091

0.887 0.058 0.057 0.063 0.517 0.114 0.474 0.491 0.498 0.068 0.074 0.423 0.557 0.778

SO4 0.258 0.953 0.914 0.909 0.424 0.614 0.515 0.515 0.476 0.597 0.744 0.553 �0.758 0.721 �0.545

0.419 0.000 0.000 0.000 0.169 0.034 0.086 0.086 0.118 0.040 0.006 0.062 0.004 0.008 0.067

t As 0.277 0.951 0.914 0.906 0.596 0.675 0.402 0.488 0.321 0.643 0.746 0.594 �0.774 0.586 �0.569 0.942

0.384 0.000 0.000 0.000 0.041 0.016 0.195 0.107 0.309 0.024 0.005 0.042 0.003 0.045 0.053 0.000

iAs 0.293 0.951 0.915 0.908 0.610 0.681 0.402 0.483 0.324 0.640 0.741 0.599 �0.769 0.590 �0.565 0.943 0.999

0.355 0.000 0.000 0.000 0.035 0.015 0.195 0.112 0.304 0.025 0.006 0.039 0.003 0.044 0.055 0.000 0.000

As-III 0.293 0.951 0.915 0.908 0.610 0.681 0.402 0.483 0.324 0.640 0.741 0.599 �0.769 0.590 �0.565 0.943 0.999 1.000

0.355 0.000 0.000 0.000 0.035 0.015 0.195 0.112 0.304 0.025 0.006 0.039 0.003 0.044 0.055 0.000 0.000 *

As-V 0.313 0.905 0.851 0.846 0.517 0.653 0.359 0.404 0.306 0.671 0.723 0.648 �0.686 0.537 �0.550 0.885 0.954 0.952 0.952

0.321 0.000 0.000 0.001 0.085 0.021 0.251 0.193 0.334 0.017 0.008 0.023 0.014 0.072 0.064 0.000 0.000 0.000 0.000

Na 0.015 0.975 0.968 0.967 0.366 0.360 0.704 0.734 0.633 0.384 0.906 0.231 �0.673 0.641 �0.560 0.902 0.871 0.870 0.870 0.829

0.963 0.000 0.000 0.000 0.242 0.250 0.011 0.007 0.027 0.218 0.000 0.470 0.016 0.025 0.058 0.000 0.000 0.000 0.000 0.001

K �0.151 0.744 0.765 0.766 0.226 0.357 0.568 0.617 0.496 0.335 0.704 0.021 �0.440 0.426 �0.661 0.677 0.627 0.624 0.624 0.486 0.763

0.639 0.006 0.004 0.004 0.480 0.254 0.054 0.032 0.101 0.288 0.011 0.949 0.153 0.168 0.019 0.016 0.029 0.030 0.030 0.109 0.004

Ca 0.286 0.782 0.773 0.769 0.767 0.655 0.242 0.383 0.140 0.543 0.596 0.551 �0.618 0.335 �0.451 0.723 0.888 0.894 0.894 0.819 0.655 0.504

0.368 0.003 0.003 0.003 0.004 0.021 0.448 0.219 0.664 0.068 0.041 0.063 0.032 0.288 0.141 0.008 0.000 0.000 0.000 0.001 0.021 0.094

Mg �0.086 0.811 0.836 0.837 0.091 0.384 0.664 0.612 0.645 0.364 0.805 0.402 �0.621 0.378 �0.411 0.829 0.798 0.793 0.793 0.809 0.754 0.566 0.645

0.790 0.001 0.001 0.001 0.779 0.218 0.018 0.035 0.023 0.244 0.002 0.195 0.031 0.225 0.184 0.001 0.002 0.002 0.002 0.001 0.005 0.055 0.024

Fe �0.276 0.178 0.249 0.238 �0.383 �0.151 0.527 0.381 0.574 �0.088 0.417 �0.050 �0.101 �0.186 �0.152 0.191 0.145 0.143 0.143 0.273 0.204 �0.042 0.028 0.536

0.386 0.580 0.435 0.456 0.219 0.640 0.078 0.221 0.051 0.785 0.177 0.878 0.754 0.562 0.638 0.552 0.654 0.657 0.657 0.390 0.525 0.897 0.931 0.072

Temp �0.673 0.292 0.410 0.421 �0.500 �0.529 0.898 0.743 0.922 �0.429 0.644 �0.492 �0.112 0.009 �0.055 0.213 0.063 0.060 0.060 0.105 0.423 0.309 �0.113 0.485 0.612

0.017 0.357 0.186 0.173 0.098 0.077 0.000 0.006 0.000 0.164 0.024 0.104 0.729 0.979 0.865 0.507 0.845 0.853 0.853 0.745 0.171 0.328 0.727 0.110 0.034

water

research

47

(2013)1005e1020

1017

wat e r r e s e a r c h 4 7 ( 2 0 1 3 ) 1 0 0 5e1 0 2 01018

5. Conclusion

In this study, different multivariate statistical techniques,

PCA, CA, SI and SAR were used to evaluate the variations in

physicochemical parameter including As and F�, of ground-

water quality in two sub districts of Tharparkar, Pakistan. It

was concluded that arsenic andfluoride concentration inmost

of the underground water samples were higher than the

permissible limits proposed by WHO. Speciation of arsenic in

groundwater plays an important role in understanding arsenic

exposure to human and animal health effects. Themean ratio

of As5þ and As3þ in most of the underground water samples

was observed about 2:1, indicated that As5þ contribute 61e68%

of total inorganic As species. The calcite, fluorite and granite

are the main minerals abundantly available and controlling

the aqueous geochemical changes in understudy area. The

alkaline environment further sustains high fluoride ions and

promotes the replacement of OH� with F� in the groundwater.

Themultivariate technique, cluster analysis of understudy

sites clearly showed the high, medium and less polluted sites

for undergroundwater. CA grouped twelve sampling sites into

three clusters on the basis of similar water quality charac-

teristics. Principle component analysis helped in identifying

the factors or sources responsible for water quality variations,

PCA results may convincingly be presumed that the contam-

ination in groundwater samples might be geologic and

climatic but not anthropogenic.

Tharparkar is also facing the crisis of water like the other

deserts of the world, underground water is available in greater

than 40 ft up to 250 ft depth, which is brackish and highly

contaminated by F�, As species and other ions. Further studies

should be focused on the bio-accumulation of As species and F�

inaquaticbiota andhazardsassociatedwith their consumption.

Authors contribution

Tasneem Gul Kazi and Hassan Imran Afridi: Made a project of

this whole research work.

Kapil Dev Brahman: Had done sampling and analyzed all

physicochemical parameters.

Shahid Naseem: Helped in to understand the geology of

study area.

Sadia Sadaf and Naeemullah: Helped in multivariate

statistical study.

Appendix A. Supplementary data

Supplementary data related to this article can be found at

http://dx.doi.org/10.1016/j.watres.2012.10.042.

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