ORIGINAL PAPER

Hydrogeochemistry of groundwater from karstic limestoneaquifer highlighting arsenic contamination: case studyfrom Jordan

Mustafa Al Kuisi1 & Abdulkader M. Abed1& Kholoud Mashal2 & Ghazi Saffarini1 &

Fathi Saqhour1

Received: 8 November 2014 /Accepted: 7 April 2015 /Published online: 28 April 2015# Saudi Society for Geosciences 2015

Abstract Groundwater wells in the Amman-Wadi Es SirAquifer (B2/A7) throughout Jordan are investigated for theirarsenic (As) and element-by-element geochemical behavior.Groundwater wells are found to have total arsenic concentra-tions above the recommended levels designated by theJordanian drinking water standard, the EnvironmentalProtection Agency of the United States, and the WorldHealth Organization. Arsenic distribution in the aquifer is var-iable, but it is detected with a concentration of ≥10 ppb in 87samples out of the analyzed 150 groundwater samples, with amaximum concentration of 173 ppb. Elevated As concentra-tions can be attributed to several mechanisms. One of thesemechanisms is accounted for to the interaction betweengroundwater and the natural phosphorite deposits in the upperpart of the aquifer and oil shale deposits overlying it. The highsignificant correlation between arsenic, phosphorus, and cal-cium concentrations in the analyzed groundwater samplessuggest that these elements are derived from the same source.

Moreover, scanning electron microscopy shows the associa-tion of As with the P and Ca in the phosphorite; pyrite ispresent in the oil shale samples, which were collected fromthe Muwaqqar formation overlying the aquifer. EDAX analy-sis shows that substantial As concentrations are present inphosphate and pyrite. This study suggests that the majormechanism responsible for releasing As from the aquifer ma-terial into the groundwater is a simple dissolution reaction.However, Piper and Durov diagrams, correlation coefficients,and factor analysis all suggest that water interaction withphosphate and oil shale deposits, sorption of heavy metals,and simple dissolution of iron oxyhydroxides are togetherthe primary factors affecting the chemistry of the groundwaterand responsible for the elevated As values in some wells.

Keywords Arsenic . Drinkingwater . Phosphorite rocks .

Groundwater . Oil shale . VisualMinteq

Introduction

Arsenic is a toxic metalloid element found in the atmosphere,surface and groundwater, aquatic food, soil, and sedimentsthat causes serious problems in the environment (Hoanget al. 2010; Larios et al. 2012). Serious health problems arelinked to chronic exposure to arsenic (As) in drinking water,which is classified as a carcinogen (Kazi et al. 2009; Rahmanet al. 2009). The Environmental Protection Agency of theUnited States and the World Health Organization set the max-imum permissible level of As for drinking water to be 10 ppb(USEPA 2012; WHO 2011).

High As concentrations are reported in natural hydrologicsystems around the globe and are typically related to geogenicsources (Mukherjee et al. 2008). Sedimentary rocks have Asconcentrations ranging from 1.7 to 400 mg/kg (Smith et al.

* Mustafa Al Kuisimkuisi@ju.edu.jo

Abdulkader M. Abedaabed@ju.edu.jo

Kholoud Mashalkholoudmashal@hotmail.com

Ghazi Saffarinighasaff@ju.edu.jo

Fathi Saqhourfshaqur@ju.edu.jo

1 Department of Applied Geology and Environment, The University ofJordan, P.O. Box: 13437, 11942 Amman, Jordan

2 Department of Land Management and Environment, The Faculty ofNatural Resources and Environment, The Hashemite University,P.O. Box 150459, Zarqa 13115, Jordan

Arab J Geosci (2015) 8:9699–9720DOI 10.1007/s12517-015-1919-z

1998), while As concentrations in igneous rocks range from1.5 to 3.0 mg/kg. Volcanic rocks, alluvial and lacustrine sed-imentary deposits, and intrusive acidic granite rocks form im-portant sources of As in groundwater (Welch et al. 1988; Bianet al. 2012; Herreraa et al. 2012). Anthropogenic pollutionalso increases As concentration in soils (Bhumbla andKeefer 1994). It is believed that the high As concentration ingroundwater is related to the interaction between water andthe aquifer rocks or minerals that contain As by either thesolubility of these minerals or the sorption of As onto solidphases. Although As is more mobile than phosphorous andoften undergoes changes in its oxidation state in soil, it has asimilar chemical behavior to P in soil, especially in aeratedsystems (Walsh et al. 1977).

Recently, the concern about As in Jordanian aquifers hasgrown tremendously, though little has been published on thisproblem. Al-Assi (2008) conducted an initial study on Asconcentration in the Amman Zarqa Basin, where she collectedand analyzed 155 groundwater samples. The study concludedthat there are natural and anthropogenic factors contributing toAs mobilization and concentration in water, including exces-sive irrigation, which strongly affects the local geo- andhydrochemical conditions in some areas.

The p r e s en t s t udy a ims to (1 ) eva lu a t e t h ehydrogeochemistry of groundwater from the B2/A7 aquifer,(2) investigate the rock/water geochemical interactions, (3)investigate As temporal variations and sources outside andwithin the B2/A7 aquifer, and (4) quantify As spatial distribu-tion in the groundwater of the B2/A7 aquifer. By doing so, inthe detected changes in As abundances and spatial variability,the pollution impact would be illustrated.

Geological and hydrogeological setting

Most of Jordan is dominated by sedimentary rocks with vary-ing thicknesses increasing from south to north (Fig. 1). ThePaleozoic deposits consist predominantly of siliciclastics:mainly sandstones (Rum Group) overlain by mixed shalesand sandstones (Khreim Group). The Rum Group constitutesthe deep sandstone aquifer throughout Jordan (Powell 1989).The Early Cretaceous Kurnub Sandstone Group unconform-ably overlies the Paleozoic strata in central and southernJordan, while in north and northwest Jordan, Triassic andJurassic sediments are found in between (Bender 1974;Powell 1989; Abed 2000).

Extensive carbonate deposits consisting of alternatinglimestone and marl were deposited during the Cenomanian-Turonian and are designated as Ajlun Group (Quennell 1951).Masri (1963) subdivided Ajlun Group into five formations,namely Na’ur, Fuheis, Hummar, Shueib, and Wadi Es Sirformations (A1 to A7 in Table 1). The Turonian Wadi Es Sir

Formation (A7) consists of limestones and forms one of thebest aquifers in Jordan.

From the Coniacian through the Late Eocene, different de-posits were laid down including bedded chert, phosphorite,organic-rich sediments, and chalk. These deposits form theBelqa Group, which was subdivided into the following for-mations: Ghudran (B1), Amman (B2),Muwaqqar (B3), Rijam(B4), and Shallaleh (B5) formations as illustrated in Table 1(El Hiyari 1985; Powell 1989; Abed 2000). The CampanianAmman Formation is an excellent shallow aquifer in Jordan. Itconsists of bedded chert alternating with limestone, overlainby phosphorites, limestone, and minor chert facies (Bender1974; Abed and Kraishan 1991; Powell and Moh’d 2011).The Amman Formation (B2) is hydraulically connected withthe Wadi Es Sir Formation (A7), forming a major shallowaquifer in Jordan, known as the B2-A7 aquifer.

Phosphorites are widespread throughout Jordan. They formpart of the Upper Cretaceous–Eocene Tethys phosphorite beltextending from the Caribbean to Iran through North Africaand the Eastern Mediterranean. The economic phosphoritehorizon in Jordan is friable or slightly cemented with calcite.It consists of sand-size phosphate particles, pellets, intraclasts,vertebrate bones, teeth, and coprolites (Abed 1994). Jordanianphosphorites are near-surface deposits, less than 40 m deep,and are mined by the open-pit method.

Hydrogeology of Amman-Wadi Sir Aquifer (B2/ A7)

In Jordan, groundwater constitutes the prime source of watersupply, as surface water is very limited. Following many yearsof drought, water resources in Jordan have been overstressedand are suffering from quantity and quality degradation formore than two decades, due to increased urban development.Recent crises in the middle east forced huge fluxes of immi-grants to move into the country either temporarily or perma-nently, exerting extra stresses on the infrastructure and thealready, quantitatively and qualitatively, exhausted water re-sources (Al Kuisi et al. 2009). Recent studies indicated a de-cline in groundwater level of about 20 to 30 m, accompaniedwith deterioration in quality during the last 3 decades (AlKuisi et al. 2009; Al Kuisi and Abdel-Fattah 2010). Suchimpacts made the protection of the resource and its manage-ment a major priority in the country.

The major aquifer systems recognized in Jordan are

(1) The deep sandstone aquifer system: dominated by sand-stones of the Paleozoic age through the Early Cretaceous(Bender 1974; Powell 1989; Abed 2000), and

(2) The Amman-Wadi Es Sir Formation (Table 1).

The Amman-Wadi Es Sir Aquifer (B2/A7) is formed ofkarstified, silicified limestone with horizons of phosphate. It

9700 Arab J Geosci (2015) 8:9699–9720

is characterized by high permeability, storage capacity, andannual recharge with a wide geographic distribution, includ-ing areas of dense population (Fig. 1). It consists of threeformations: Amman Formation (B2), Ghudran Formation(B1), and Wadi Sir Formation (A7). The three formationsare hydraulically connected and are considered as one aquifer

unit. The B2/A7 aquifer is characterized by karstificationwhich results in the enlargement of joints and fissures. Thethickness of the B2/A7 unit may reach up to more than 300 min the Dhuleil-Hallabat area, northeast Jordan.

The aquifer is essentially an unconfined one with someparts of it confined. The depth of water table ranges from

Fig. 1 A simplified geological map of Jordan

Arab J Geosci (2015) 8:9699–9720 9701

100 m in the south to about 150 m in the northern plateau. Thegroundwater flow in the aquifer is from the south to the northand northwest. The effective porosity for the B2/A7 aquiferranges between 10 and 30 % for the unconfined part of theaquifer, while the storage coefficient for the confined part isabout 5×10−5 (NWMP 2004).

The B2/A7 aquifer is highly exploited by wells ranging indepth from 50 m to more than 600 m. In the south nearEshidiya, well depths range from 240 to 300 m. These wellsare penetrating four different formations: Alluvium, RijamFormation (B4), Muwaqqar Formation (B3), and Amman-Wadi Es Sir formations (B2/A7). The same formations arepenetrated in the middle of Jordan near Hasa, Al Abiad,Karak, Muha, As Sultani, and Al Qatranah. The casing forthe upper reaches of these wells is 13.4 in., with separatesections of 8.6-in. diameters installed at depths greater than160–200 m. The casing material is usually steel.

Materials and methods

Sampling and water analyses

Groundwater samples were collected from 150 wells penetrat-ing the B2/A7 aquifer between May 2009 and July 2011.These wells represent ten well-defined fields as shown inFig. 2. The depth of wells in these fields exceeds 100 m.

Samples were collected after pumping for about 30 min toensure obtaining representative uncontaminated water samples.Temperature (°C), pH, electrical conductivity (EC; μS/cm), re-dox potential (Eh mV), and dissolved oxygen (DO; mg/L) were

measured on site, as well, using WTW-portable instruments.Alkalinity was measured on site by titrating water samples with0.2 M H2SO4. The water samples were collected in polyethyl-ene bottles and transported to the laboratory and stored at 4 °C.Water samples were acidified using concentrated analytical-grade HNO3 for analysis of trace elements to prevent chemicalprecipitation (0.5 mL in 500 mL bottle to achieve pH 2).

Major cations and anions in addition to phosphorous wereanalyzed. Anions were analyzed using ion chromatograph(Shimadzu), and the cations were analyzed using flame emis-sion photometer at the laboratories of the University of Jordan,following standard methods (Arnold et al. 1998). Estimateddetection limits for each constituent are shown in Table 2.Quality control samples included replicates and field blanks.Replicate samples were collected after the routine sampling inthe field, and all differences measured in concentrations be-tween replicate pairs were within the precision of the method.

The anion/cation balances of all samples are within ±5 %.These samples were placed without filtering in 250-mL poly-ethylene bottles, previously treated with trace metal-grade ni-tric acid diluted to 50 % with double-deionized water, for aperiod of 3 days. No concentrated analytical-grade nitric acidwas added to the bottles, which have been used for analyzingmajor cations and anions. Bottles were sealed in doublezipper-locked bags before and after sampling. Unfiltered wa-ter samples were analyzed with the aid of an inductivelycoupled plasma-mass spectrometry (ICP-MS) at theUniversity RWTH—Aachen in Germany and ACMELaboratories in Canada for a suite of elements including As,B, Ba, Br, Cd, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Rb, Se, Si, Sr, Ce,U, and V.

Table 1 Nomenclature of the Cretaceous Formations and the stratigraphic position of Amman-Wadi Es Sir formations (Masri 1963; El Hiyari 1985)

Age Group Formation Member

Tertiary Eocene Belqa Wadi Shallaleh (B5)

Um Rijam ChertLimestone (B4)

Paleocene Muwaqqar ChalkMarl (B3)Late Cretaceous Maastrichtian

Amman (B2) B2b Phosphorite FaciesCampanian

B2a Chert FaciesSantonian

Coniacian Ghudran (B1) Dhiban Chalk

Tafila

Mujib Chalk

Turonian Ajlun Wadi Es Sir (A7)

Shueib (A5–6)

Cenomanian Hummar (A4)

Fuheis (A3)

Na’ur (A1–2)

Early Cretaceous Aptian-Albian Kurnub (Hathira)Sandstone Group

9702 Arab J Geosci (2015) 8:9699–9720

The ICP-MS was calibrated using a series of three externalstandards of these elements with concentrations ranging from0.001 to 100 mg/L, and standard curves for all elementsdisplaying Pearson correlation coefficients >0.99 were pre-pared. The standard set was analyzed both before and after

every set of 25 unknown water samples to verify consistencyin instrument response and lack of signal drift. Concentrationsof trace elements in each water sample were determined intriplicates; the reported values represent the averages of thetriplicate analyses. In addition, 20 rock samples collected from

Fig. 2 Location map for the sampled water wells

Arab J Geosci (2015) 8:9699–9720 9703

the different formations were analyzed for major and traceelements by Acme Analytical Laboratories in Vancouver,Canada. To understand the chemical composition of mineralscontaining As in the studied area, 10 samples of phosphateand oil shale formations were studied by an ESEM FEIQuanta 600 FEG scanning electron microscope, operated inlow-vacuum mode (0.6 mbar), such that gold- or carbon-sputtering was not necessary. A Genesis 4000 EDAX wasused for chemical characterization.

PhreeqC (Parkhurst 1995) and Visual Minteq (Allison et al.1991) computer programs were used in order to detect thespecies and minerals of arsenic and calculate the saturationindex of the different mineral phases present in the aquifer.The significant results for the different calculated parametersbased on the whole analysis are presented in Table 7.

The analyzed variables were subjected to multivariate sta-tistical treatment techniques using STATISTICA™ software(8.0) to study their inter-elemental relationships.

Results and discussion

General water chemical analyses

The results of the chemical analyses of the collected ground-water samples with maximum permissible limits (MPL) fordrinking purposes according to the Jordanian Institute ofStandards and Metrology (JISM, 2008) are summarized inTable 3. Table 4 shows the average elemental concentrationsin the already-defined well fields. The pH values range from6.98 to 8.2. Field-measured redox potential ranges from −271to +910 mV. Electrical conductivity (EC) ranges from 485 to1829 μS/cm. The high salinity values of the groundwatersamples suggest a high rock/water interaction, though it couldalso be due to over pumping and/or external pollution in the

studied areas (Al Kuisi et al. 2009; Al Kuisi and Abdel-Fattah2010).

The temperature in groundwater wells ranged from 24.6 to32.5 °C (Table 4). In Eshidiya and Al Lajjun well fields,groundwater samples had higher temperatures than normal(30.17 and 28.29 °C, respectively). The waters of these wellfields are usually aerated to decrease the water temperatureand eliminate undesirable gases like H2S before use. Ca2+,Na+, Cl−, and HCO3

− are the most dominant ions in the sam-ples (Table 3). In 87 of water samples (58 %), the abundanceof the cations is in the following order Ca>Na>Mg>K. Thesecations generally show an increasing trend along groundwaterflow path, while the remaining 42% of the samples follow theabundance order Na>Ca>Mg>K. Sodium concentrationranges from 22.21 to 278.9 ppm with an average of70.34 ppm (Table 3). The average Na concentration is belowthe Jordanian standards for drinking purposes (JISM 2008);however, in some wells, it is higher than the JISM.

Calcium and magnesium concentrations in groundwatervary from 59.55 to 144.49 and 21.60 to 75.53 ppm aver-aging 89.03 and 43.32 ppm, respectively, with high cor-relation coefficient of 0.80 between the two cations(Tables 3 and 5). This high correlation suggests that Caand Mg are derived from the same source, namely fromthe dissolution of calcite and dolomite in B2/A7. Calciummagnesium mass ratios of most groundwater samplesrange from 1.5 to 2.2, indicating that dolomites have con-tributed solutes to the groundwater as represented by theequation below:

CaMg CO3ð Þ2 þ 2H2CO3↔4HCO−3 þ Ca2þ þMg2þ ð1Þ

Potassium concentration in groundwater varies from 0.91to 13.26 ppm with an average of about 3.67 ppm (Table 3).Potassium input into the groundwater is attributed to K fertil-izers and clay minerals associated with aquifer rocks.

Table 2 Analytical methods used for measuring parameters

Parameter Unit Analytical method Detection limitsb Reference and method number

EC, pH value, DO temp. μS/cm, mg/L, °C Field EC, pH, DO,T meter WTW instrument

Standard Methods, 20th edition 2510 Ba

HCO3− ppm Titrimetric method 0.1 In-house standard operating procedure

Cl− ppm Ion chromatograph 0.01 Standard Methods, 20th edition 4110 Ba

NO3−, SO4

2− ppm Ion chromatograph 0.292 and 0.04

PO43− ppb Stannous chloride 0.001 Standard Methods, 20th edition 4500 D/P

Ca, Na, K, Mg ppm ICP-MS 0.05, 0.05, 0.05, and 0.05b Standard Methods, 20th edition 3125 Aa

As, B, Ba, Br, Cd, Ce, Cr,Cu, Fe, Li, Mn, Pb, Rb,Se, Si, Sr U, V

ppb ICP-MS 0.5, 5, 0.05, 5, 0.05, 0.01,0.5, 0.1, 10, 0.1, 0.05,0.1, 0.01, 0.5, 40, 0.01,0.02, and 0.2b

Standard Methods, 20th edition 3125 Aa

a Arnold et al. 1998bValues given by Acme Analytical Laboratories in Vancouver, Canada, and RWTH-Aachen University in Germany

9704 Arab J Geosci (2015) 8:9699–9720

Anion test results show the abundance orders of HCO3−>

Cl−>SO42−>NO3

− and Cl−>HCO3−>SO4

2−>NO3−.

Bicarbonate and chloride are the dominant ions in the studyfields ranging from 217.77 to 522.65 ppm and 9.3 to324.0 ppm with average concentrations of 352.68 and124.33 ppm, respectively (Table 3). The concentration ofchloride can be attributed to the irrigation return flow andoverexploitation of the different aquifers, while the source ofbicarbonate is attributed to natural processes such asweathering of carbonate as illustrated below.

CaCO3 þ CO2 þ H2O↔Ca2þ þ 2HCO−3 ð2Þ

Sulfate concentration in the tested wells varies from 26.0 to164.0 ppm (Table 3), that is much less than the maximumpermissible limit of 500 ppm as given by the Jordanian

drinking water standard. The relatively high sulfate in someprivate wells can be related to agricultural activities (ammoni-um sulfate fertilizer).

The nitrate concentration ranges from 11 to 63 ppmwith an average of 42 ppm. The higher nitrate concentra-tion is mainly attributed to intensive application of fertil-izers in agricultural land and treated waste water effluentsin areas overlying shallow water tables. The major sourceof pollution is attributed to a major waste water treatmentplant (WWTP) known as As-Samra located 45 km north-east of Amman City. Recently, a study showed that thewells around the WWTP are contaminated by nitrate up to73 % above the threshold level (70 ppm) and are consid-ered very saline, reaching 91 % above the salinity thresh-old level (1500 μS/cm) (Al Kuisi et al 2009).

Table 3 Summary of groundwater chemical composition of B2/A7 Aquifer (n=150)

Parameter Mean Minimum Maximum JISM permissible level (2008)

EC (μS/cm) 903.22 485.00 1829.00 1500

pH 7.29 6.98 8.20 6.5–8.5

Eh (mV) 103.65 −271.0 910.0

DO (mg/L) 4.35 1.35 9.73

Temp (°C) 26.76 20.0 40.80

As (ppb) 20.16 1.70 175.00 0.01 ppm

B (ppb) 178.88 47.00 542.00 1 ppm

Ba (ppb) 72.18 32.22 147.53 1 ppm

Br (ppb) 508.74 190.00 1020.00 1 ppm

Ca (ppm) 89.03 59.55 145.49 200 ppm

Cd (ppb) 0.43 0.05 4.03 0.003 ppm

Ce (ppb) 0.17 0.01 6.17 0.005 ppm

Cl (ppm) 124.35 9.30 324.00 500 ppm

Cr (ppb) 21.25 0.90 167.30 0.05 ppm

Cu (ppb) 5.97 0.40 76.80 1 ppm

Fe (ppb) 969.51 10.00 19,327.00 1 ppm

HCO3− (ppm) 352.68 217.77 522.65 250 ppm

K (ppm) 3.67 0.91 13.26 10 ppm

Li (ppb) 11.70 2.00 55.00 0.1 ppm

Mg (ppm) 43.32 21.60 75.53 50 ppm

Mn (ppb) 14.17 0.31 179.55 0.01 ppm

Na (ppm) 70.34 22.21 278.91 200 ppm

NO3− (ppm) 42 11 63 70 ppm

PO43− (ppb) 18.81 0.03 124.60 0.001 ppm

Pb (ppb) 4.35 0.30 28.00 0.01 ppm

Rb (ppb) 2.99 0.47 11.48 0.01 ppm

SO42− (ppm) 50.47 26.00 164.00 500 ppm

Se (ppb) 30.06 1.00 667.40 0.01 ppm

Si (ppm) 7.59 5.56 10.31 0.1 ppm

Sr (ppm) 1.17 0.30 2.96 0.01 ppm

U (ppb) 2.88 0.02 32.11 0.01 ppm

V (ppb) 42.73 1.60 523.60 0.01 ppm

Arab J Geosci (2015) 8:9699–9720 9705

Tab

le4

Average

chem

icalcompositio

nof

groundwater

inthe10

wellfields

Param

eter

RusefiaandZarqa

areas

Qatranaharea

Lajjunarea

MuhaandKarak

area

Sultaneharea

WadiA

lAbyad

area

Hasaarea

Shobakarea

Jafararea

Eshidiyaarea

EC(μS/cm

)1371

948.13

999.00

966.63

1046.00

965.00

1017.00

686.78

616.92

1208.70

pH7.44

7.04

7.39

7.53

7.07

7.26

7.56

7.54

7.44

7.27

Eh(m

V)

444.5

187.88

−33.00

152.06

91.71

176.33

119.60

173.83

184.25

−200.90

Do(m

g/L)

7.62

3.95

2.11

3.98

2.76

3.46

3.36

5.98

4.12

1.80

Temp(°C)

24.6

26.38

28.29

27.67

28.89

29.57

32.84

22.64

23.11

30.17

As(ppb)

11.3

9.05

27.61

14.06

29.69

21.83

31.56

22.23

13.62

21.15

B(ppb)

219

210.75

235.25

151.44

191.00

179.00

221.20

73.28

79.00

409.90

Ba(ppb)

55.6

59.14

61.94

81.56

83.12

84.09

93.43

84.33

66.60

42.87

Br(ppb)

444

590.00

791.17

566.69

597.00

583.33

555.60

325.50

295.58

490.10

Ca(ppm

)138

88.55

109.06

85.38

97.51

88.09

98.52

71.89

64.97

120.56

Cd(ppb)

0.24

0.40

0.31

0.55

0.78

0.49

0.24

0.39

0.49

0.22

Ce(ppb)

0.05

0.04

0.12

0.05

0.15

0.02

0.06

0.49

0.03

0.22

Cl(ppm)

239

94.23

112.38

162.69

144.96

53.00

31.72

127.29

119.51

155.28

Cr(ppb)

11.9

10.63

12.09

45.74

35.47

23.17

7.46

7.91

22.39

20.58

Cu(ppb)

2.9

3.09

7.01

10.93

11.11

2.53

2.40

4.91

2.29

4.68

Fe(ppb)

366

650.75

919.33

1853.75

630.29

193.00

1741.40

667.56

221.08

1396.00

HCO3−(ppm

)447

348.43

422.84

362.04

320.43

326.66

300.52

300.57

317.58

372.38

K(ppm

)12.2

3.00

2.84

3.21

3.61

2.71

3.52

2.77

2.30

9.61

Li(ppb)

19.8

11.19

12.08

10.73

13.07

9.20

11.22

7.50

5.64

28.06

Mg(ppm

)81.2

44.22

51.55

40.65

45.75

41.44

49.46

34.99

30.40

63.27

Mn(ppb)

27.1

28.89

12.55

18.17

8.61

3.12

48.67

8.09

2.94

12.27

Na(ppm

)205.9

87.56

91.32

62.79

97.92

93.03

110.03

34.25

30.55

110.23

NO3−(ppm

)46.9

12.61

9.63

39.98

13.64

14.16

14.75

14.56

47.45

11.5

PO43−(ppb)

3833.88

99.83

26.38

77.43

71.00

111.20

123.39

37.17

59.60

Pb(ppb)

5.6

1.38

3.04

2.92

5.31

1.63

1.18

7.55

3.08

8.12

Rb(ppb)

3.1

2.23

2.37

2.49

2.81

2.45

2.82

2.02

1.34

9.21

SO42−(ppm

)63.6

104.43

113.3

48.26

72.98

84.32

72.60

19.67

102

136

Se(ppb)

11.2

21.35

9.88

68.82

73.16

48.43

23.48

20.29

13.52

4.32

Si(ppm

)6.5

7.41

7.86

7.73

7.84

7.85

7.52

7.00

6.62

9.21

Sr(ppm

)1.65

1.41

1.27

0.96

1.54

1.28

1.41

0.70

0.55

2.36

U(ppb)

3.89

4.35

1.80

3.06

10.21

4.16

2.52

1.88

1.78

0.52

V(ppb)

10.5

47.64

26.93

50.93

185.56

88.03

14.12

19.26

20.23

14.63

9706 Arab J Geosci (2015) 8:9699–9720

Tab

le5

Correlatio

ncoefficientm

atrixforpartof

themajor

andtraceelem

entsin

thestudiedwater.R

edhighlig

hted

correlations

aresignificantatthe

95%

significance

level(n=150)

Parameter

EC

(μS/cm

)

pHEh

(mV)

HCO3−

(ppm

)

As

(ppm

)

Ca

(ppm

)

Cd

(ppb)

Ce

(ppb)

Cl

(ppm

)

Co

(ppb)

Cr

(ppb)

Cu

(ppb)

Fe (ppm

)

K (ppm

)

Mg

(ppm

)

Mn

(ppb)

Na

(ppm

)

NO3−

(ppm

)

PO43−

(ppb)

Pb (ppb)

Rb

(ppb)

SO42−

(ppm

)

Se (ppm

)

Si (ppm

)

Sr

(ppb)

U (ppb)

V (ppb)

EC(μS/cm

)1.00

pH0.20

1.00

Eh(m

V)

−0.16

−0.17

1.00

HCO3−

(ppm

)0.53

−0.26

0.11

1.00

As(ppm

)0.04

0.10

−0.06

0.41

1.00

Ca(ppm

)0.89

−0.04

−0.07

0.65

0.65

1.00

Cd(ppb)

−0.02

0.09

0.06

0.13

0.48

0.34

1.00

Ce(ppb)

0.07

0.18

−0.07

0.79

0.30

0.40

1.00

Cl(ppm)

0.91

−0.15

−0.01

0.42

0.07

0.34

0.04

0.04

1.00

Co(ppb)

0.17

0.16

−0.02

0.06

0.33

0.20

0.26

0.47

0.59

1.00

Cr(ppb)

0.16

0.25

0.06

0.03

0.15

0.02

0.08

0.07

0.71

0.65

1.00

Cu(ppb)

0.26

0.15

0.06

0.06

0.17

0.08

−0.03

0.24

0.32

0.38

0.34

1.00

Fe(ppm

)0.14

0.26

−0.50

0.21

0.05

−0.01

−0.08

0.35

−0.06

0.25

−0.10

0.17

1.00

K(ppm

)0.40

−0.43

−0.20

0.09

−0.01

−0.06

−0.12

−0.01

0.08

−0.08

−0.17

−0.06

0.05

1.00

Mg(ppm

)0.76

−0.10

−0.05

0.39

0.27

0.80

−0.04

0.22

0.24

0.20

0.01

0.23

−0.07

−0.03

1.00

Mn(ppb)

−0.17

0.02

−0.42

0.03

−0.10

−0.36

−0.08

0.08

−0.13

0.22

−0.26

−0.05

0.57

0.23

−0.30

1.00

Na(ppm

)0.93

−0.13

−0.31

0.44

0.12

0.44

−0.08

0.06

0.89

−0.12

−0.28

−0.09

0.01

0.16

0.52

−0.01

1.00

NO3−

(ppm

)0.62

−0.06

−0.21

−0.55

0.39

0.46

0.08

0.11

0.42

0.05

0.04

0.06

0.11

0.37

0.38

0.05

0.31

1.00

PO43−

(ppb)

−0.01

0.06

−0.11

0.21

0.84

0.80

0.36

0.67

−0.18

0.11

−0.11

0.03

0.14

−0.04

0.30

−0.07

0.23

0.23

1.00

Pb(ppb)

0.04

−0.08

−0.25

0.09

0.59

0.21

0.46

0.58

0.11

0.33

0.05

0.21

0.13

0.09

0.11

0.12

0.02

0.05

0.38

1.00

Rb(ppb)

−0.05

−0.15

−0.63

0.06

−0.04

−0.29

−0.17

−0.04

0.02

−0.08

−0.16

−0.11

0.38

0.52

−0.27

0.61

0.27

0.06

−0.03

0.19

1.00

SO42−

(ppm

)0.32

−0.17

−0.39

0.46

0.31

0.57

−0.05

0.19

0.23

0.12

−0.08

−0.04

0.23

0.17

0.66

0.02

0.72

0.65

0.34

0.16

0.28

1.00

Se(ppm

)0.69

0.37

0.04

0.22

−0.59

−0.05

0.10

0.02

−0.05

0.08

0.14

0.19

0.12

−0.20

−0.11

−0.14

−0.14

0.40

−0.08

−0.02

−0.21

−0.21

1.00

Si(ppm

)−0

.01

0.02

−0.62

0.06

0.15

−0.16

−0.02

0.16

0.05

0.01

−0.08

0.05

0.47

0.34

−0.23

0.39

0.17

0.04

0.15

0.24

0.84

0.27

−0.05

1.00

Sr(ppb)

0.23

−0.19

−0.15

0.55

0.39

0.58

0.00

0.24

0.20

0.19

−0.04

0.01

0.01

0.01

0.78

−0.12

0.54

0.19

0.41

0.10

−0.06

0.80

−0.21

−0.07

1.00

U(ppb)

0.13

0.14

0.14

0.18

0.65

0.35

0.86

0.56

0.03

0.33

0.07

0.01

−0.09

−0.12

0.07

−0.11

0.07

0.04

0.48

0.48

−0.18

0.01

0.19

−0.05

0.09

1.00

V(ppb)

0.10

0.04

−0.02

0.08

0.16

0.14

0.57

0.31

−0.03

0.06

0.06

0.29

−0.05

−0.01

0.02

−0.04

0.19

0.03

0.21

0.17

−0.06

0.02

0.40

0.11

0.05

0.87

1.00

Arab J Geosci (2015) 8:9699–9720 9707

Fig. 3 Arsenic distributions in tested water samples

9708 Arab J Geosci (2015) 8:9699–9720

Fig. 4 Piper and Durov diagrams illustrating the results of the

Arab J Geosci (2015) 8:9699–9720 9709

High phosphate concentration is recorded in the range of0.03 to 124.6 ppb with an average 18.81 ppb. This high con-centration is attributed to the phosphate present in the upperpart of the B2/A7 and to the use of fertilizers. In general,heavy metal concentrations in the water samples from thedifferent areas show concentrations below the maximum per-missible limits (JISM 2008) (Table 3).

Arsenic showed significant positive correlations with Cd(r=0.48), Ce (r=0.79), NO3

− (r=0.39), Pb (r=0.59), Sr (r=0.39), and U (r=0.65) (Table 5) suggesting a common originfor these elements.

Iron concentrations range between 10.00 and 19,327 ppbwith an average value of 969.51 ppb. These low iron concen-trations can be explained by the redox potential of the ana-lyzed samples being oxidized or slightly reduced. The high Feconcentrations in some wells might be due to the reductivedissolution of Fe-oxyhydroxide indicated by the significantnegative correlation with the Eh (r=−0.50).

The majority of groundwater had two hydrochemical facies,Ca–Mg–HCO3 andNa, Ca–SO4, Cl in the Piper diagram (Piper

1944) (Fig. 3a). This means that the chemical composition ofthe groundwater is affected mainly by recharge water,carbonate-phosphate mineral dissolution, and some anthropo-genic pollution like irrigation return flow. Ca–HCO3 typeshows a significant positive correlation with pH, Ca2+, SO4

2−,PO4

3−, and HCO3− mainly in waters with elevated As concen-

tration (>10 ppb) (Table 5). This is a good indication of thesame source. Furthermore, in the Durov diagram, the values ofthe cations and the anions are plotted in the appropriate triangleand projected into the square of the main field, which displayssome possible geochemical processes that could affect the wa-ter genesis. Figure 3b shows the results of the Durov diagrams,which represent a simple dissolution and mixing fields. Thissimple dissolution and mixing line support the proposed expla-nation for Piper classification for the water samples.

Arsenic geochemistry and behavior

Arsenic concentration in the water samples ranges from 1.70to 175.0 ppb (Table 3) and exhibits a north-south increasing

Table 6 Average composition ofthe raw phosphorite samples(n=20)

Parameter Unit Central Jordan Abied area Al Hasa area Eshidiya area

SiO2 % 10.05 4.29 22.23 9.13

Al2O3 0.67 0.46 1.56 0.26

Fe2O3 0.435 0.24 0.72 0.15

MgO 0.3 0.34 0.57 0.18

CaO 48.5 52.24 40.84 50.55

Na2O 0.58 0.43 0.28 0.53

K2O 0.06 0.06 0.07 0.04

TiO2 0.035 0.04 0.08 0.02

P2O5 29.8 27.32 23 33.01

MnO 0.01 0.01 0.03 0.04

LOI 9.25 14.35 10.4 5.9

TOT/C 2.03 3.39 2.2 1.14

TOT/S 0.46 0.22 0.16 0.44

As ppm 23 25 27 20

Cd 5.5 35 18 5

Co 0.6 0.7 1.4 0.5

Cr 144.5 138.5 99 59

Cu 12.5 15.5 10 10

Hg 0.015 1.15 1.7 1

Mo 15 27.5 19 7

Ni 9 0.06 0.01 0.01

Pb 3 3 2.2 1.1

Se 1 0.7 0.5 0.8

Sr 1767.5 1263 834 1052

Th 3.3 1.05 1 0.5

U 65.5 175 34 46

V 87 188 65 55

Zn 154.5 159.5 116 93

9710 Arab J Geosci (2015) 8:9699–9720

trend (Fig. 4), with an average of 20.16 ppb, which is higherthan the 10.0 ppb safe limit recommended by the JISM (2008)andWorld health Organization (WHO 2011). Arsenic concen-trations showed variation among the wells in different areas,where 87 of the samples are above this maximum permissiblelimit, while the rest of the investigated wells have low Asconcentration. The average total As concentrations in thegroundwater of the 10 studied localities ranges from 9.05 to31.56 ppb (Table 4) exceeding thus the JISM and WHO max-imum permissible limit. These high averages of As concentra-tions can be attributed to several mechanisms that govern theAs concentration in this aquifer.

To understand these mechanisms, 20 rock samples contain-ing phosphate from contaminated localities were analyzed fortheir major and trace elements (Table 6). Arsenic contentranges between 20 and 27 ppm. The high significant correla-tion of As with PO4

3− (R2=0.84) (Fig. 5a) and Ca2+ (R2=0.78)

(Fig. 5b) in the water samples support the idea that they camefrom the same origin. This clearly indicates the association ofAs with the P and Ca in the phosphorite, most probablysubstituting P in the apatite structure. Ca was found to corre-late positively with PO4

3− (R2=0.80) (Fig. 5c). On the otherhand, the positive relationship between Ca and As (Fig. 5c) ispossibly due to the dissolution of apatite (francolite) (carbon-ate fluorapatite) where appreciable amounts of As are dissolv-ing, which might reflect rock/water interaction increasing inthe direction of groundwater flow. In the studied areas, thepresence of francolite was confirmed by SEM (Fig. 6).Moreover, pyrite was present as framboids generally less than10 μm in the oil shale samples, which were collected from theMuwaqqar Formation overlying the aquifer. The SES analysisshowed that substantial As concentrations were present inphosphate and pyrite (Figs. 6 and 7). The substitution of Asfor P has already been evidenced by many authors, e.g.,

Fig. 5 a, b, c Correlation of As versus a PO43− and b Ca2+, and c PO4

3− versus Ca2+

Arab J Geosci (2015) 8:9699–9720 9711

Fig. 6 Scanning electron micrographs of phosphate

9712 Arab J Geosci (2015) 8:9699–9720

Hughes and Drexler (1991), Lazareva and Pichler (2007), andLi et al. (2002).

In literature, it was hypothesized that desorption might alsobe responsible for the variation in As concentration among

Fig. 7 Scanning electron micrographs of framboidal pyrite in oil

Arab J Geosci (2015) 8:9699–9720 9713

these areas. The highest average concentration of As is detect-ed in Hasa area, which is characterized by high values ofphosphate, sulfate, and boron. Kouras et al. 2007 recorded apositive relationship between As and boron in groundwater.Negatively charged ions such as phosphate and sulfate poten-tially compete with As for adsorption sites. In this study, mostattention has been given to phosphate, which certainly affectsthe behavior of As as indicated by a high positive correlation(Fig. 5a). Despite their opposed toxic and life-supporting na-tures, the chemistries of arsenate and phosphate have much incommon. Both arsenate As (V) and arsenite As (III) desorp-tion are pH-dependent. Phosphate also influences As adsorp-tion onto ferrihydrite, depending on its oxidation state:Phosphate reduces As (III) adsorption at low pH, (Jain andLoeppert 2000) and decreases adsorption of As (V) at high pH(Jain and Loeppert 2000). However, these experiments wereconducted at much higher concentrations than are normal innature, and so, the effect will be small in most practicalsituations. Dixit and Hering (2003) also showed that, in thepresence of phosphate, As (V) and As (III) sorption ontoamorphous and crystalline Fe compound is almost the same

over the pH range of 4–10. Phosphate has similar effects onadsorption by both goethite and ferrihydrite (Manning andGoldberg 1996). It is possible that high phosphate concentra-tions might reduce the adsorption of As (V) in alkaline-oxicwaters but have only a small effect in near-neutral reducingwaters. Therefore, competition for sorption sites by phosphateappear to sustain elevated aqueous As levels in the upperaquifer. Furthermore, past or ongoing reductive dissolutionof Fe3+ oxyhydroxides acts synergistically with competitivesorption to maintain elevated dissolved As levels in the loweraquifer (Swartz et al. 2004).

Reducing conditions in some wells may result in the mo-bilization and release of As from many types of solids (Welchet al. 2000; Nickson et al. 2000), while under oxidizing con-ditions in the wells, As may adsorb onto Fe oxides, sulfideminerals, and organic matter in groundwater (Welch et al.2000; Kim et al. 2000). Arsenic concentrations were plottedon an Eh-pH diagram (Fig. 8) using the Geochemist’sWorkbench 6.0. They fall in three stability fields. The fallingof our samples in three redox phases suggests that both oxicand suboxic conditions predominate in the unconfined portion

Fig. 8 Thermodynamic stability fields for the different locations

9714 Arab J Geosci (2015) 8:9699–9720

of the aquifer, whereas suboxic conditions predominate alongthe middle reaches of the flow path, and anoxic/sulfidic con-ditions predominate in the most down-gradient portions of theaquifer.

The significant result encountered is that As was found tobe saturated with respect to aragonite, calcite, dolomite, he-matite, and goethite but under-saturated with respect to anhy-drite, gypsum, celestite, barite, anglesite, cerussite, halite, hy-droxyapatite, magnesite, pyrolusite, rhodochrosite, siderite,smithsonite, and strontianite (Table 7). By linking, theresults of As concentrations and the results derived from thegeochemical model illustrated the high As concentrationsindicating that As in the groundwater is influenced bynatural sources like the presence of phosphate and oil shalein the geological units above the aquifer.

According to van Geen et al. (2004), reductive dissolutionand mobilization of As(III) can also occur in less reducingenvironments or even oxic environments. Anaerobic metal-reducing bacteria could play a catalytic role in mobilizationof As from basin sediments (Islam et al. 2004). Several studiesshowed a moderate to strong correlation between As and Fe,as expected from reductive dissolution of FeOOH withadsorbed As (Nickson et al. 1998), locally up to r=0.8–0.9.However, in this study, Fe correlates weakly with As (r=0.25)(Fig. 9). Such weak correlations suggest that reduction of Asand Fe may not be simultaneous. Also, some of the As re-leased by reductive dissolution of (Fe/Mn)–OOH can be re-

sorbed to the residual or partially reduced metal (hydr)oxides(McArthur et al. 2004), and cycles of reduction and re-oxidation of Fe and S species can cause preferential immobi-lization of As (Zheng et al. 2004). Arsenic in the present studyis also not correlated with Mn, in contrast to previous studies(Ahmed et al. 2004). This lack of correlation suggests that nosingle mechanism (such as reductive dissolution or pH-dependent desorption) can explain As mobilization in thestudy area.

Violante and Pigna (2002) showed how phosphate variablyreduces the adsorption of arsenate (but not arsenite) on a va-riety of oxides, clays, and soils in the pH range of 4–8. Mosttested minerals adsorbed similar quantities of arsenate andphosphate; however, Fe, Mn, and Ti oxides and Fe-rich clayminerals (such as smectite and nontronite) retained arsenatemore strongly than phosphate. On the other hand, Al-richminerals such as gibbsite, boehmite, amorphous Al hydroxide,and the clay minerals allophane, kaolinite, and halloysiteretained phosphate more strongly than arsenate. Al Kuisiand Abdel-Fattah (2010) reported that the deterioration of soiland groundwater quality is a result mainly of Se–As fertilizersuse due to excessive P application, overdosing of soil withphosphate, and undesirable additions of selenium and arsenicin P fertilizers.

Statistical analysis

The relationships between As, Fe, and SO4 constituents areshown in Fig. 9. This figure shows that there is a significantpositive correlation between As and Fe (0.46), and As andSO4 (0.56). R-mode factor analysis was applied to investigatethe interrelationships between the analyzed elements and pa-rameters. The analyzed data sets were grouped into a fewfactors describing variability of the tested elements and pa-rameters. Three factors were extracted from the analyzed ele-ments and parameters, and they accounted for 82.5 % of thetotal variance in this data set. Parameters with marked loading(more than 0.5) were taken into considerations for factor anal-yses. Therefore, some parameters are not present in Table 8,while they are present in Fig. 10. The three extracted factors(with eigenvalues ≥1) are presented in Table 8 and listedbelow:

Factor 1: Named rock/water interaction factor and loadedwith EC, B, Br, Ca, Mg, Na, K, Li, Rb, SO4, Si,and Sr.

Factor 2: Sorption factor, loaded with pH, Ba, Cd, Cu, Fe,Cl, HCO3, Ni, Mn, Mo, Pb, Se, U, V, Br, and Cr.

Factor 3: Phosphate factor, loaded with As, Ce, and PO4.

On the other hand, correlations between oblique factors(clusters of variables with unique loadings) were performedfor these factors and are presented in Fig. 10, which is a

Table 7 The calculated saturation index of the different mineral phasesin the aquifer

Parameter Minimum Maximum Mean Standarddeviation

SI anhydrite −2.71 0.300 −1.918 0.425

SI aragonite −0.910 2.780 0.353 0.450

SI calcite −0.770 2.920 0.495 0.540

SI dolomite −1.500 5.690 1.045 1.036

SI gypsum −2.510 0.490 −1.708 0.425

SI celestite −4.490 −1.080 −2.016 0.595

SI barite −3.160 0.430 −0.115 0.600

SI anglesite −8.870 −2.950 −5.668 0.771

SI cerussite −3.060 −1.270 −2.328 0.391

SI halite −9.460 −5.520 −6.457 0.833

SI hematite 13.480 21.970 17.090 1.535

SI hydroxyapatite −17.900 1.950 −2.716 3.166

SI magnesite −8.360 −3.640 −7.075 1.064

SI pyrolusite −13.370 12.390 −11.036 4.016

SI rhodochrosite −9.100 1.860 −1.673 1.488

SI siderite −3.040 1.860 −1.673 1.488

SI smithsonite −3.480 0.540 −0.822 0.846

SI strontianite −3.48 0.54 −0.822 0.846

SI goethite 5.730 9.980 7.524 0.773

Arab J Geosci (2015) 8:9699–9720 9715

pictorial representation of the variables influenced by factors1, 2, and 3.

Factor 1: rock/water interaction factor This factor has highloading on electrical conductivity and most of the major ana-lyzed variables such as EC, B, Br, Ca,Mg, Na, K, Li, Rb, SO4,Si, and Sr (Fig. 10). It represents 35.12 % of the total variance

within the data set. Potassium, Rb, Si, and Ba clearly representthe clays in the aquifer rocks, while Ca, Mg, and Sr belong tothe carbonates and phosphorites. Sodium and SO4

2− areknown to substitute for Ca2+ and PO4

3−, respectively, in thefrancolite (carbonate fluorapatite) structure. Therefore, thisfactor represents the interaction between the groundwaterand the rocks of the aquifer. Any increase in the concentration

Fig. 9 Bivariate relationship ofAs versus a Fe and b SO4

2−

9716 Arab J Geosci (2015) 8:9699–9720

of these variables will increase the electrical conductivity dueto the dissolution of aquifer matrix or due to the addition ofother sources (irrigation return flow or overexploitation of theaquifer).Factor 2: sorption factor This factor is loaded withpH, Ba, Cd, Cu, Fe, Cl, HCO3, Ni, Mn, Mo, Pb, Se, U, V, Br,and Cr. It is dominated by heavy metals that are most likelyadsorbed on the clay minerals and/or the organic matter of theaquifer rocks. However, some of these elements such as U andV are known, at least partially, to substitute for Ca in thefrancolite structure (Moh’d and Powell 2010; Abed andSadaqah 2012). These metals can be liberated to the aquifer

through the interaction with the rock material in a similarmanner as those of factor 1. This explains the significant cor-relation between the two factors (Fig. 10).

Factor 3: phosphate factor This factor is loaded with As,Ce, and PO4

3−and solves 17.08 of the total variability in thedata set (Table. 8). This is a straightforward factor because Caand PO4 are the major constituents of the francolite crystalstructure. Cerium and most rare earth elements are known tosubstitute for Ca in the francolite structure (McArthur 1985;Abed and AbuMurrey 1997). Li et al. (2002) and Hughes andDrexler (1991) report the substitution of As for P. In this study,As most likely substituted P in the crystal structure offrancolite, as indicated by the high significant positive corre-lation with PO4

3− discussed previously and shown in Table 5(Lazareva and Pichler 2007). It seems that these four elementswere liberated from the phosphates to the groundwater of theaquifer proportionally. However, the significant positive cor-relation between As and PO4

3− can be accounted for by suit-able Eh-pH values that keep both ions dissolved in the waterof the studied aquifer (Abed et al. 2008; Abed and Sadaqah2012; Brookings 1988).

Conclusions

The main objective of this study is to investigate As occur-rences and sources within Amman-Wadi Es Sir Aquifer (B2/A7) of Jordan. The average total As concentration in theAmman-Wadi Es Sir (B2/A7) aquifer in Jordan exceeded thesafe limit designated by the Jordanian drinking water stan-dard, the US EPA, and the WHO. The concentration of Aswas ≥10 ppb in 87 samples out of 150, with a maximumconcentration of 173 ppb. Accordingly, the chronic exposureto such elevated concentrations might inflect serious healthproblems.

The geochemical and statistical treatment of the data re-vealed the following:

1. The data show that the highest As concentrations are lo-cated in the Al Hasa area, which has a heavy miningactivity. According to our study, the raw phosphorite sam-ples contained up to 27 mg/kg As, and there was a strongcorrelation between As, P, and Ca, suggesting that theseelements were derived from the same source. Moreover,the SEM images of representative phosphorite and oilshale samples show the association of As with P and Ca,and the EDAX analysis showed that substantial As con-centrations were present in phosphate and pyrite.

2. This study suggests that As enrichment in phosphate rockfound in the aquifer formation and oil shale samples in thesoils above the aquifer accounts for the release of a sig-nificant amount of As and transport to the groundwater

Table 8 Factors for hierarchical analysis and loadings of the analyzedelements and parameters

Parameter Factor 1 Factor 2 Factor 3

EC (μS/cm) 0.896

pH

Eh (mV)

Temp (°C)

As (ppb) 0.829

B (ppb) 0.910

Ba (ppb)

Br (ppb) 0.590

Ca (ppm) 0.890

Cd (ppb) 0.615

Ce (ppb) 0.884

Cl (ppm)

Cr (ppb)

Cu (ppb)

Fe (ppb)

HCO3− (ppm)

K (ppm) 0.680

Li (ppb) 0.740

Mg (ppm) 0.949

Mn (ppb)

Na (ppm) 0.864

NO3− (ppm) 0.632

PO4−3(ppb) 0.873

Pb (ppb)

Rb (ppb) 0.725

SO4−2(ppm) 0.935

Se (ppb) 0.531

Si (ppm) 0.728

Sr (ppm) 0.877

U (ppb) 0.789

V (ppb) 0.763

Eigenvalue 7.36 3.45 2.24

% total 35.12 19.12 17.08

Cumulative 35.12 54.24 71.32

Arab J Geosci (2015) 8:9699–9720 9717

via formation of arseno-carbonate complexes. Moreover,other mechanisms can be called upon to account for theelevated As concentration in some wells such as the sim-ple dissolution of iron oxyhydroxides.

3. The results of factor analysis indicate that there arethree factors that explain about 82.5 % of the variancein the dataset. The analysis clearly shows the associ-ation of As with the phosphorite factor. These factorsare

Factor 1: Interaction factor, loaded with EC, B,Br, Ca, Mg, Na, K, Li, Rb, SO4,Si, and Sr.

Factor 2: Sorption factor, loaded with pH, Ba, Cd, Cu,Fe, Cl, HCO3, Ni, Mn, Mo, Pb, Se, U, V, Br,and Cr.

Factor 3: Phosphate factor, loaded with As, Ce, andPO4.

4. The aquifer has been found to be saturated with aragonite,calcite, dolomite, hematite, and goethite. However, theaquifer was under-saturated with anhydrite, gypsum, ce-lestite, barite, anglesite, cerussite, halite, hydroxyapatite,magnesite, pyrolusite, rhodochrosite, siderite, smithson-ite, and strontianite. From geochemical modeling, we ob-served that there are many minerals constituting oil shale

and phosphate beds such as calcite, quartz, kaolinite, do-lomite, gypsum, pyrite, and apatite. Dissolution of theseminerals releases considerable As concentration to thegroundwater aquifer.

5. Ca2+, Na+, Cl−, and HCO3− are the most dominant ions in

the samples. In 87 water samples (58 %), the abundanceof the cations is in the following order Ca>Na>Mg>K,while the remaining 42 % of the samples follow the abun-dance order Na>Ca>Mg>K. On the other hand, aniontest results show the abundance orders of HCO3

−>Cl−>SO4

2−>NO3− and Cl−>HCO3

−>SO42−>NO3

−. However,the cations and anions generally show an increasing trendalong groundwater flow path. Using Piper classificationreveals that the great majority of groundwater exhibitstwo hydrochemical facies, Ca–Mg–HCO3 and Na, Ca–SO4, Cl. This means that the chemical composition ofthe groundwater is affected mainly by recharge water,carbonate-phosphate oil shale minerals dissolution, andsome anthropogenic pollution like irrigation return flow.

6. The concentrations of other cations in most of the ground-water samples were below the maximum permissiblelimits of the JISM and WHO guidelines.

Acknowledgments Thanks are due to the anonymous reviewers of thisjournal for highly improving the manuscript. Thanks and gratitude is also

Fig. 10 3D representation of thefactors: salinity, sorption, andphosphate

9718 Arab J Geosci (2015) 8:9699–9720

due to the Deanship of Scientific Research at the University of Jordan forsupporting and sponsoring this research. This research has been accom-plished during the sabbatical leave offered to the senior author from theUniversity of Jordan starting February 2014–January 2015.

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