Arab J Geosci DOI 10.1007/s12517-015-1919-z
ORIGINAL PAPER
Hydrogeochemistry of groundwater from karstic limestone aquifer highlighting arsenic contamination: case study from Jordan Mustafa Al Kuisi 1 & Abdulkader M. Abed 1 & Kholoud Mashal 2 & Ghazi Saffarini 1 & Fathi Saqhour 1
Received: 8 November 2014 / Accepted: 7 April 2015 # Saudi Society for Geosciences 2015
Abstract Groundwater wells in the Amman-Wadi Es Sir Aquifer (B2/A7) throughout Jordan are investigated for their arsenic (As) and element-by-element geochemical behavior. Groundwater wells are found to have total arsenic concentrations above the recommended levels designated by the Jordanian drinking water standard, the Environmental Protection Agency of the United States, and the World Health Organization. Arsenic distribution in the aquifer is variable, but it is detected with a concentration of ≥10 ppb in 87 samples out of the analyzed 150 groundwater samples, with a maximum concentration of 173 ppb. Elevated As concentrations can be attributed to several mechanisms. One of these mechanisms is accounted for to the interaction between groundwater and the natural phosphorite deposits in the upper part of the aquifer and oil shale deposits overlying it. The high significant correlation between arsenic, phosphorus, and calcium concentrations in the analyzed groundwater samples suggest that these elements are derived from the same source.
Moreover, scanning electron microscopy shows the association of As with the P and Ca in the phosphorite; pyrite is present in the oil shale samples, which were collected from the Muwaqqar formation overlying the aquifer. EDAX analysis shows that substantial As concentrations are present in phosphate and pyrite. This study suggests that the major mechanism responsible for releasing As from the aquifer material into the groundwater is a simple dissolution reaction. However, Piper and Durov diagrams, correlation coefficients, and factor analysis all suggest that water interaction with phosphate and oil shale deposits, sorption of heavy metals, and simple dissolution of iron oxyhydroxides are together the primary factors affecting the chemistry of the groundwater and responsible for the elevated As values in some wells. Keywords Arsenic . Drinking water . Phosphorite rocks . Groundwater . Oil shale . Visual Minteq
Introduction * Mustafa Al Kuisi
[email protected] Abdulkader M. Abed
[email protected] Kholoud Mashal
[email protected] Ghazi Saffarini
[email protected] Fathi Saqhour
[email protected] 1
Department of Applied Geology and Environment, The University of Jordan, P.O. Box: 13437, 11942 Amman, Jordan
2
Department of Land Management and Environment, The Faculty of Natural Resources and Environment, The Hashemite University, P.O. Box 150459, Zarqa 13115, Jordan
Arsenic is a toxic metalloid element found in the atmosphere, surface and groundwater, aquatic food, soil, and sediments that causes serious problems in the environment (Hoang et al. 2010; Larios et al. 2012). Serious health problems are linked to chronic exposure to arsenic (As) in drinking water, which is classified as a carcinogen (Kazi et al. 2009; Rahman et al. 2009). The Environmental Protection Agency of the United States and the World Health Organization set the maximum permissible level of As for drinking water to be 10 ppb (USEPA 2012; WHO 2011). High As concentrations are reported in natural hydrologic systems around the globe and are typically related to geogenic sources (Mukherjee et al. 2008). Sedimentary rocks have As concentrations ranging from 1.7 to 400 mg/kg (Smith et al.
Arab J Geosci
1998), while As concentrations in igneous rocks range from 1.5 to 3.0 mg/kg. Volcanic rocks, alluvial and lacustrine sedimentary deposits, and intrusive acidic granite rocks form important sources of As in groundwater (Welch et al. 1988; Bian et al. 2012; Herreraa et al. 2012). Anthropogenic pollution also increases As concentration in soils (Bhumbla and Keefer 1994). It is believed that the high As concentration in groundwater is related to the interaction between water and the aquifer rocks or minerals that contain As by either the solubility of these minerals or the sorption of As onto solid phases. Although As is more mobile than phosphorous and often undergoes changes in its oxidation state in soil, it has a similar chemical behavior to P in soil, especially in aerated systems (Walsh et al. 1977). Recently, the concern about As in Jordanian aquifers has grown tremendously, though little has been published on this problem. Al-Assi (2008) conducted an initial study on As concentration in the Amman Zarqa Basin, where she collected and analyzed 155 groundwater samples. The study concluded that there are natural and anthropogenic factors contributing to As mobilization and concentration in water, including excessive irrigation, which strongly affects the local geo- and hydrochemical conditions in some areas. The present study aims to (1) evaluate the hydrogeochemistry of groundwater from the B2/A7 aquifer, (2) investigate the rock/water geochemical interactions, (3) investigate As temporal variations and sources outside and within the B2/A7 aquifer, and (4) quantify As spatial distribution in the groundwater of the B2/A7 aquifer. By doing so, in the 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 varying thicknesses increasing from south to north (Fig. 1). The Paleozoic deposits consist predominantly of siliciclastics: mainly sandstones (Rum Group) overlain by mixed shales and sandstones (Khreim Group). The Rum Group constitutes the deep sandstone aquifer throughout Jordan (Powell 1989). The Early Cretaceous Kurnub Sandstone Group unconformably overlies the Paleozoic strata in central and southern Jordan, while in north and northwest Jordan, Triassic and Jurassic sediments are found in between (Bender 1974; Powell 1989; Abed 2000). Extensive carbonate deposits consisting of alternating limestone and marl were deposited during the CenomanianTuronian 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 Sir formations (A1 to A7 in Table 1). The Turonian Wadi Es Sir
Formation (A7) consists of limestones and forms one of the best aquifers in Jordan. From the Coniacian through the Late Eocene, different deposits were laid down including bedded chert, phosphorite, organic-rich sediments, and chalk. These deposits form the Belqa Group, which was subdivided into the following formations: 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 Campanian Amman Formation is an excellent shallow aquifer in Jordan. It consists of bedded chert alternating with limestone, overlain by phosphorites, limestone, and minor chert facies (Bender 1974; Abed and Kraishan 1991; Powell and Moh’d 2011). The Amman Formation (B2) is hydraulically connected with the Wadi Es Sir Formation (A7), forming a major shallow aquifer in Jordan, known as the B2-A7 aquifer. Phosphorites are widespread throughout Jordan. They form part of the Upper Cretaceous–Eocene Tethys phosphorite belt extending from the Caribbean to Iran through North Africa and the Eastern Mediterranean. The economic phosphorite horizon 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). Jordanian phosphorites 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 water supply, as surface water is very limited. Following many years of drought, water resources in Jordan have been overstressed and are suffering from quantity and quality degradation for more than two decades, due to increased urban development. Recent crises in the middle east forced huge fluxes of immigrants to move into the country either temporarily or permanently, exerting extra stresses on the infrastructure and the already, quantitatively and qualitatively, exhausted water resources (Al Kuisi et al. 2009). Recent studies indicated a decline in groundwater level of about 20 to 30 m, accompanied with deterioration in quality during the last 3 decades (Al Kuisi et al. 2009; Al Kuisi and Abdel-Fattah 2010). Such impacts made the protection of the resource and its management a major priority in the country. The major aquifer systems recognized in Jordan are (1) The deep sandstone aquifer system: dominated by sandstones 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 of karstified, silicified limestone with horizons of phosphate. It
Arab J Geosci
Fig. 1 A simplified geological map of Jordan
is characterized by high permeability, storage capacity, and annual recharge with a wide geographic distribution, including areas of dense population (Fig. 1). It consists of three formations: Amman Formation (B2), Ghudran Formation (B1), and Wadi Sir Formation (A7). The three formations are hydraulically connected and are considered as one aquifer
unit. The B2/A7 aquifer is characterized by karstification which results in the enlargement of joints and fissures. The thickness of the B2/A7 unit may reach up to more than 300 m in the Dhuleil-Hallabat area, northeast Jordan. The aquifer is essentially an unconfined one with some parts of it confined. The depth of water table ranges from
Arab J Geosci Table 1
Nomenclature of the Cretaceous Formations and the stratigraphic position of Amman-Wadi Es Sir formations (Masri 1963; El Hiyari 1985)
Tertiary
Late Cretaceous
Age
Group
Formation
Eocene
Belqa
Wadi Shallaleh (B5) Um Rijam Chert Limestone (B4) Muwaqqar Chalk Marl (B3) Amman (B2)
Paleocene Maastrichtian Campanian Santonian Coniacian
Turonian
Ghudran (B1)
Ajlun
Cenomanian
Early Cretaceous
Aptian-Albian
100 m in the south to about 150 m in the northern plateau. The groundwater flow in the aquifer is from the south to the north and northwest. The effective porosity for the B2/A7 aquifer ranges between 10 and 30 % for the unconfined part of the aquifer, while the storage coefficient for the confined part is about 5×10−5 (NWMP 2004). The B2/A7 aquifer is highly exploited by wells ranging in depth from 50 m to more than 600 m. In the south near Eshidiya, well depths range from 240 to 300 m. These wells are penetrating four different formations: Alluvium, Rijam Formation (B4), Muwaqqar Formation (B3), and AmmanWadi Es Sir formations (B2/A7). The same formations are penetrated in the middle of Jordan near Hasa, Al Abiad, Karak, Muha, As Sultani, and Al Qatranah. The casing for the upper reaches of these wells is 13.4 in., with separate sections of 8.6-in. diameters installed at depths greater than 160–200 m. The casing material is usually steel.
Materials and methods Sampling and water analyses Groundwater samples were collected from 150 wells penetrating the B2/A7 aquifer between May 2009 and July 2011. These wells represent ten well-defined fields as shown in Fig. 2. The depth of wells in these fields exceeds 100 m. Samples were collected after pumping for about 30 min to ensure obtaining representative uncontaminated water samples. Temperature (°C), pH, electrical conductivity (EC; μS/cm), redox potential (Eh mV), and dissolved oxygen (DO; mg/L) were
Member
B2b B2a Dhiban Chalk Tafila Mujib Chalk
Phosphorite Facies Chert Facies
Wadi Es Sir (A7) Shueib (A5–6) Hummar (A4) Fuheis (A3) Na’ur (A1–2) Kurnub (Hathira) Sandstone Group
measured on site, as well, using WTW-portable instruments. Alkalinity was measured on site by titrating water samples with 0.2 M H2SO4. The water samples were collected in polyethylene bottles and transported to the laboratory and stored at 4 °C. Water samples were acidified using concentrated analyticalgrade HNO3 for analysis of trace elements to prevent chemical precipitation (0.5 mL in 500 mL bottle to achieve pH 2). Major cations and anions in addition to phosphorous were analyzed. Anions were analyzed using ion chromatograph (Shimadzu), and the cations were analyzed using flame emission photometer at the laboratories of the University of Jordan, following standard methods (Arnold et al. 1998). Estimated detection 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 in the field, and all differences measured in concentrations between 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 polyethylene bottles, previously treated with trace metal-grade nitric acid diluted to 50 % with double-deionized water, for a period of 3 days. No concentrated analytical-grade nitric acid was added to the bottles, which have been used for analyzing major cations and anions. Bottles were sealed in double zipper-locked bags before and after sampling. Unfiltered water samples were analyzed with the aid of an inductively coupled plasma-mass spectrometry (ICP-MS) at the University RWTH—Aachen in Germany and ACME Laboratories 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.
Arab J Geosci
Fig. 2 Location map for the sampled water wells
The ICP-MS was calibrated using a series of three external standards of these elements with concentrations ranging from 0.001 to 100 mg/L, and standard curves for all elements displaying Pearson correlation coefficients >0.99 were prepared. The standard set was analyzed both before and after
every set of 25 unknown water samples to verify consistency in instrument response and lack of signal drift. Concentrations of trace elements in each water sample were determined in triplicates; the reported values represent the averages of the triplicate analyses. In addition, 20 rock samples collected from
Arab J Geosci Table 2
Analytical methods used for measuring parameters
Parameter
Unit
Analytical method
μS/cm, mg/L, °C Field EC, pH, DO, T meter WTW instrument HCO3− ppm Titrimetric method Cl− ppm Ion chromatograph − 2− NO3 , SO4 ppm Ion chromatograph PO43− ppb Stannous chloride Ca, Na, K, Mg ppm ICP-MS As, B, Ba, Br, Cd, Ce, Cr, ppb ICP-MS Cu, Fe, Li, Mn, Pb, Rb, Se, Si, Sr U, V
Detection limitsb
Reference and method number Standard Methods, 20th edition 2510 Ba
EC, pH value, DO temp.
0.1 0.01 0.292 and 0.04 0.001 0.05, 0.05, 0.05, and 0.05b 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
In-house standard operating procedure Standard Methods, 20th edition 4110 Ba Standard Methods, 20th edition 4500 D/P Standard Methods, 20th edition 3125 Aa Standard Methods, 20th edition 3125 Aa
a
Arnold et al. 1998
b
Values given by Acme Analytical Laboratories in Vancouver, Canada, and RWTH-Aachen University in Germany
the different formations were analyzed for major and trace elements by Acme Analytical Laboratories in Vancouver, Canada. To understand the chemical composition of minerals containing As in the studied area, 10 samples of phosphate and oil shale formations were studied by an ESEM FEI Quanta 600 FEG scanning electron microscope, operated in low-vacuum mode (0.6 mbar), such that gold- or carbonsputtering was not necessary. A Genesis 4000 EDAX was used for chemical characterization. PhreeqC (Parkhurst 1995) and Visual Minteq (Allison et al. 1991) computer programs were used in order to detect the species and minerals of arsenic and calculate the saturation index of the different mineral phases present in the aquifer. The significant results for the different calculated parameters based on the whole analysis are presented in Table 7. The analyzed variables were subjected to multivariate statistical 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 groundwater samples with maximum permissible limits (MPL) for drinking purposes according to the Jordanian Institute of Standards and Metrology (JISM, 2008) are summarized in Table 3. Table 4 shows the average elemental concentrations in the already-defined well fields. The pH values range from 6.98 to 8.2. Field-measured redox potential ranges from −271 to +910 mV. Electrical conductivity (EC) ranges from 485 to 1829 μS/cm. The high salinity values of the groundwater samples suggest a high rock/water interaction, though it could also be due to over pumping and/or external pollution in the
studied areas (Al Kuisi et al. 2009; Al Kuisi and Abdel-Fattah 2010). The temperature in groundwater wells ranged from 24.6 to 32.5 °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 well fields are usually aerated to decrease the water temperature and eliminate undesirable gases like H2S before use. Ca2+, Na+, Cl−, and HCO3− are the most dominant ions in the samples (Table 3). In 87 of water samples (58 %), the abundance of the cations is in the following order Ca>Na>Mg>K. These cations generally show an increasing trend along groundwater flow path, while the remaining 42 % of the samples follow the abundance order Na >Ca >Mg>K. Sodium concentration ranges from 22.21 to 278.9 ppm with an average of 70.34 ppm (Table 3). The average Na concentration is below the Jordanian standards for drinking purposes (JISM 2008); however, in some wells, it is higher than the JISM. Calcium and magnesium concentrations in groundwater vary from 59.55 to 144.49 and 21.60 to 75.53 ppm averaging 89.03 and 43.32 ppm, respectively, with high correlation coefficient of 0.80 between the two cations (Tables 3 and 5). This high correlation suggests that Ca and Mg are derived from the same source, namely from the dissolution of calcite and dolomite in B2/A7. Calcium magnesium mass ratios of most groundwater samples range from 1.5 to 2.2, indicating that dolomites have contributed solutes to the groundwater as represented by the equation below: Ca MgðCO3 Þ2 þ 2H2 CO3 ↔4HCO−3 þ Ca2þ þ Mg2þ
ð1Þ
Potassium concentration in groundwater varies from 0.91 to 13.26 ppm with an average of about 3.67 ppm (Table 3). Potassium input into the groundwater is attributed to K fertilizers and clay minerals associated with aquifer rocks.
Arab J Geosci Table 3
Summary of groundwater chemical composition of B2/A7 Aquifer (n=150)
Parameter
Mean
Minimum
Maximum
JISM permissible level (2008)
EC (μS/cm) pH Eh (mV) DO (mg/L) Temp (°C) As (ppb) B (ppb) Ba (ppb) Br (ppb) Ca (ppm) Cd (ppb) Ce (ppb) Cl (ppm) Cr (ppb) Cu (ppb) Fe (ppb) HCO3− (ppm)
903.22 7.29 103.65 4.35 26.76 20.16 178.88 72.18 508.74 89.03 0.43 0.17 124.35 21.25 5.97 969.51
485.00 6.98 −271.0 1.35 20.0 1.70 47.00 32.22 190.00 59.55 0.05 0.01 9.30 0.90 0.40 10.00
1829.00 8.20 910.0 9.73 40.80 175.00 542.00 147.53 1020.00 145.49 4.03 6.17 324.00 167.30 76.80 19,327.00
1500 6.5–8.5
0.01 ppm 1 ppm 1 ppm 1 ppm 200 ppm 0.003 ppm 0.005 ppm 500 ppm 0.05 ppm 1 ppm 1 ppm
352.68
217.77
522.65
250 ppm
K (ppm) Li (ppb) Mg (ppm) Mn (ppb) Na (ppm) NO3− (ppm) PO43− (ppb) Pb (ppb) Rb (ppb) SO42− (ppm) Se (ppb) Si (ppm) Sr (ppm) U (ppb) V (ppb)
3.67 11.70 43.32 14.17 70.34 42 18.81 4.35 2.99 50.47 30.06 7.59 1.17 2.88 42.73
0.91 2.00 21.60 0.31 22.21 11 0.03 0.30 0.47 26.00 1.00 5.56 0.30 0.02 1.60
13.26 55.00 75.53 179.55 278.91 63 124.60 28.00 11.48 164.00 667.40 10.31 2.96 32.11 523.60
10 ppm 0.1 ppm 50 ppm 0.01 ppm 200 ppm 70 ppm 0.001 ppm 0.01 ppm 0.01 ppm 500 ppm 0.01 ppm 0.1 ppm 0.01 ppm 0.01 ppm 0.01 ppm
Anion test results show the abundance orders of HCO3− > Cl > SO 4 2 − > NO 3 − and Cl − > HCO 3 − > SO 4 2 − > NO 3 − . Bicarbonate and chloride are the dominant ions in the study fields ranging from 217.77 to 522.65 ppm and 9.3 to 324.0 ppm with average concentrations of 352.68 and 124.33 ppm, respectively (Table 3). The concentration of chloride can be attributed to the irrigation return flow and overexploitation of the different aquifers, while the source of bicarbonate is attributed to natural processes such as weathering of carbonate as illustrated below. −
CaCO3 þ CO2 þ H2 O↔Ca2þ þ 2HCO−3
ð2Þ
Sulfate concentration in the tested wells varies from 26.0 to 164.0 ppm (Table 3), that is much less than the maximum permissible limit of 500 ppm as given by the Jordanian
drinking water standard. The relatively high sulfate in some private wells can be related to agricultural activities (ammonium sulfate fertilizer). The nitrate concentration ranges from 11 to 63 ppm with an average of 42 ppm. The higher nitrate concentration is mainly attributed to intensive application of fertilizers in agricultural land and treated waste water effluents in areas overlying shallow water tables. The major source of pollution is attributed to a major waste water treatment plant (WWTP) known as As-Samra located 45 km northeast of Amman City. Recently, a study showed that the wells around the WWTP are contaminated by nitrate up to 73 % above the threshold level (70 ppm) and are considered very saline, reaching 91 % above the salinity threshold level (1500 μS/cm) (Al Kuisi et al 2009).
Mn (ppb) Na (ppm) NO3− (ppm) PO43− (ppb) Pb (ppb) Rb (ppb) SO42− (ppm) Se (ppb) Si (ppm) Sr (ppm) U (ppb) V (ppb)
27.1 205.9 46.9 38 5.6 3.1 63.6 11.2 6.5 1.65 3.89 10.5
348.43 3.00 11.19 44.22
447 12.2 19.8 81.2
K (ppm) Li (ppb) Mg (ppm)
187.88 3.95 26.38 9.05 210.75 59.14 590.00 88.55 0.40 0.04 94.23 10.63 3.09 650.75
444.5 7.62 24.6 11.3 219 55.6 444 138 0.24 0.05 239 11.9 2.9 366
Eh (mV) Do (mg/L) Temp (°C) As (ppb) B (ppb) Ba (ppb) Br (ppb) Ca (ppm) Cd (ppb) Ce (ppb) Cl (ppm) Cr (ppb) Cu (ppb) Fe (ppb) HCO3− (ppm)
28.89 87.56 12.61 33.88 1.38 2.23 104.43 21.35 7.41 1.41 4.35 47.64
948.13 7.04
1371 7.44
EC (μS/cm) pH
Qatranah area
Rusefia and Zarqa areas
12.55 91.32 9.63 99.83 3.04 2.37 113.3 9.88 7.86 1.27 1.80 26.93
18.17 62.79 39.98 26.38 2.92 2.49 48.26 68.82 7.73 0.96 3.06 50.93
362.04 3.21 10.73 40.65
152.06 3.98 27.67 14.06 151.44 81.56 566.69 85.38 0.55 0.05 162.69 45.74 10.93 1853.75
−33.00 2.11 28.29 27.61 235.25 61.94 791.17 109.06 0.31 0.12 112.38 12.09 7.01 919.33 422.84 2.84 12.08 51.55
966.63 7.53
Muha and Karak area
999.00 7.39
Lajjun area
Average chemical composition of groundwater in the 10 well fields
Parameter
Table 4
8.61 97.92 13.64 77.43 5.31 2.81 72.98 73.16 7.84 1.54 10.21 185.56
320.43 3.61 13.07 45.75
91.71 2.76 28.89 29.69 191.00 83.12 597.00 97.51 0.78 0.15 144.96 35.47 11.11 630.29
1046.00 7.07
Sultaneh area
3.12 93.03 14.16 71.00 1.63 2.45 84.32 48.43 7.85 1.28 4.16 88.03
326.66 2.71 9.20 41.44
176.33 3.46 29.57 21.83 179.00 84.09 583.33 88.09 0.49 0.02 53.00 23.17 2.53 193.00
965.00 7.26
Wadi Al Abyad area
48.67 110.03 14.75 111.20 1.18 2.82 72.60 23.48 7.52 1.41 2.52 14.12
300.52 3.52 11.22 49.46
119.60 3.36 32.84 31.56 221.20 93.43 555.60 98.52 0.24 0.06 31.72 7.46 2.40 1741.40
1017.00 7.56
Hasa area
8.09 34.25 14.56 123.39 7.55 2.02 19.67 20.29 7.00 0.70 1.88 19.26
300.57 2.77 7.50 34.99
173.83 5.98 22.64 22.23 73.28 84.33 325.50 71.89 0.39 0.49 127.29 7.91 4.91 667.56
686.78 7.54
Shobak area
2.94 30.55 47.45 37.17 3.08 1.34 102 13.52 6.62 0.55 1.78 20.23
317.58 2.30 5.64 30.40
184.25 4.12 23.11 13.62 79.00 66.60 295.58 64.97 0.49 0.03 119.51 22.39 2.29 221.08
616.92 7.44
Jafar area
12.27 110.23 11.5 59.60 8.12 9.21 136 4.32 9.21 2.36 0.52 14.63
372.38 9.61 28.06 63.27
−200.90 1.80 30.17 21.15 409.90 42.87 490.10 120.56 0.22 0.22 155.28 20.58 4.68 1396.00
1208.70 7.27
Eshidiya area
Arab J Geosci
0.09
−0.02
0.07
0.91
0.17
0.16
0.26
0.14
0.40
Cd (ppb)
Ce (ppb)
Cl (ppm)
Co (ppb)
Cr (ppb)
Cu (ppb)
Fe (ppm)
K (ppm)
Mg (ppm)
−0.20
−0.05
−0.42
−0.31
−0.11
−0.25
−0.43
−0.10
0.02
−0.13
−0.06
0.06
0.76
−0.17
0.93
0.62
−0.01
Mn (ppb)
Na (ppm)
NO3− (ppm)
PO43− (ppb)
−0.15
−0.19
0.23
0.13
0.10
Sr (ppb)
U (ppb)
V (ppb)
0.04
0.14
−0.62
0.02
−0.01
Si (ppm)
0.18 0.08
−0.02
0.55
0.06
0.22
0.46
0.06
0.09
0.21
−0.55
0.44
0.03
0.39
0.14
0.04
0.37
0.69
Se (ppm)
−0.39
−0.17
0.32
−0.15
−0.05
Rb (ppb)
SO42− (ppm)
−0.63
−0.08
0.04
Pb (ppb)
−0.21
0.21
−0.50
0.26 0.09
0.06
0.06
0.15
0.25
0.03
−0.02
0.06
0.06
−0.01
−0.15
0.16
0.42
−0.07
0.13
0.18
0.06
0.41 0.65
−0.07
−0.04
0.89
Ca (ppm)
1.00
0.11
HCO3− (ppm)
−0.06
0.04
As (ppm)
1.00
Eh (mV)
0.10
0.53
HCO3− (ppm)
−0.26
1.00
−0.17
0.20
−0.16
Eh (mV)
1.00
EC (μS/cm)
pH
pH
EC (μS/cm)
0.16
0.65
0.39
0.14
0.35
0.58
−0.16
−0.05
−0.59 0.15
0.57
−0.29
0.21
0.80
0.46
0.44
−0.36
0.80
−0.06
−0.01
0.08
0.02
0.20
0.34
0.30
0.34
1.00
Ca (ppm)
0.31
−0.04
0.59
0.84
0.39
0.12
−0.10
0.27
−0.01
0.05
0.17
0.15
0.33
0.07
0.79
0.48
0.65
1.00
As (ppm)
0.57
0.86
0.00
−0.02
0.10
−0.05
−0.17
0.46
0.36
0.08
−0.08
−0.08
−0.04
−0.12
0.31
0.56
0.24
0.16
0.02
0.19
−0.04
0.58
0.67
0.11
0.06
0.08
0.22
−0.01
0.35
0.24
−0.03 −0.08
0.07
0.47
0.04
1.00
Ce (ppb)
0.08
0.26
0.04
0.40
1.00
Cd (ppb)
−0.03
0.03
0.20
0.05
−0.05
0.23
0.02
0.11
−0.18
0.42
0.89
−0.13
0.24
0.08
−0.06
0.32
0.71
0.59
1.00
Cl (ppm)
0.06
0.33
0.19
0.01
0.08
0.12
−0.08
0.33
0.11
0.05
−0.12
0.22
0.20
−0.08
0.25
0.38
0.65
1.00
Co (ppb)
0.06
0.07
−0.04
−0.08
0.14
−0.08
−0.16
0.05
−0.11
0.04
−0.28
−0.26
0.01
−0.17
−0.10
0.34
1.00
Cr (ppb)
0.29
0.01
0.01
0.05
0.19
−0.04
−0.11
0.21
0.03
−0.01
−0.12
−0.09 −0.05
0.01
0.34
−0.20
0.17
0.52
0.09
−0.04
0.37
0.16
0.23
−0.03
1.00
K (ppm)
0.01
0.47
0.12
0.23
0.38
0.13
0.14
0.11
0.01
−0.09 0.06
0.57
−0.07
0.05
1.00
Fe (ppm)
−0.05
0.23
−0.06
0.17
1.00
Cu (ppb)
0.02
0.07
0.78
−0.23
−0.11
0.66
−0.27
0.11
0.30
0.38
0.52
−0.30
1.00
Mg (ppm)
−0.04
−0.11
−0.12
0.39
−0.14
0.02
0.61
0.12
−0.07
0.05
−0.01
1.00
Mn (ppb)
0.19
0.07
0.54
0.17
−0.14
0.72
0.27
0.02
0.23
0.31
1.00
Na (ppm)
0.03
0.04
0.19
0.04
0.40
0.65
0.06
0.05
0.23
1.00
NO3− (ppm)
0.21
0.48
0.41
0.15
−0.08
0.34
−0.03
0.38
1.00
PO43− (ppb)
0.17
0.48
0.10
0.24
−0.02
0.16
0.19
1.00
Pb (ppb)
−0.06
−0.18
−0.06
0.84
−0.21
0.28
1.00
Rb (ppb)
0.02
0.01
0.80
0.27
−0.21
1.00
SO42− (ppm)
0.40
0.19
−0.21
−0.05
1.00
Se (ppm)
0.11
−0.05
−0.07
1.00
Si (ppm)
0.05
0.09
1.00
Sr (ppb)
Correlation coefficient matrix for part of the major and trace elements in the studied water. Red highlighted correlations are significant at the 95 % significance level (n=150)
Parameter
Table 5
0.87
1.00
U (ppb)
1.00
V (ppb)
Arab J Geosci
Arab J Geosci
Fig. 3 Arsenic distributions in tested water samples
Arab J Geosci
Fig. 4 Piper and Durov diagrams illustrating the results of the
Arab J Geosci Table 6 Average composition of the raw phosphorite samples (n=20)
Parameter
Unit
Central Jordan
Abied area
Al Hasa area
Eshidiya area
SiO2 Al2O3 Fe2O3 MgO CaO
%
10.05 0.67 0.435 0.3 48.5
4.29 0.46 0.24 0.34 52.24
22.23 1.56 0.72 0.57 40.84
9.13 0.26 0.15 0.18 50.55
0.58 0.06 0.035 29.8 0.01 9.25 2.03 0.46 23 5.5 0.6 144.5 12.5 0.015 15 9 3 1
0.43 0.06 0.04 27.32 0.01 14.35 3.39 0.22 25 35 0.7 138.5 15.5 1.15 27.5 0.06 3 0.7
0.28 0.07 0.08 23 0.03 10.4 2.2 0.16 27 18 1.4 99 10 1.7 19 0.01 2.2 0.5
0.53 0.04 0.02 33.01 0.04 5.9 1.14 0.44 20 5 0.5 59 10 1 7 0.01 1.1 0.8
1767.5 3.3 65.5 87 154.5
1263 1.05 175 188 159.5
834 1 34 65 116
1052 0.5 46 55 93
Na2O K2O TiO2 P2O5 MnO LOI TOT/C TOT/S As Cd Co Cr Cu Hg Mo Ni Pb Se Sr Th U V Zn
ppm
High phosphate concentration is recorded in the range of 0.03 to 124.6 ppb with an average 18.81 ppb. This high concentration is attributed to the phosphate present in the upper part of the B2/A7 and to the use of fertilizers. In general, heavy metal concentrations in the water samples from the different areas show concentrations below the maximum permissible 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 origin for these elements. Iron concentrations range between 10.00 and 19,327 ppb with an average value of 969.51 ppb. These low iron concentrations can be explained by the redox potential of the analyzed samples being oxidized or slightly reduced. The high Fe concentrations in some wells might be due to the reductive dissolution of Fe-oxyhydroxide indicated by the significant negative correlation with the Eh (r=−0.50). The majority of groundwater had two hydrochemical facies, Ca–Mg–HCO3 and Na, Ca–SO4, Cl in the Piper diagram (Piper
1944) (Fig. 3a). This means that the chemical composition of the groundwater is affected mainly by recharge water, carbonate-phosphate mineral dissolution, and some anthropogenic pollution like irrigation return flow. Ca–HCO3 type shows a significant positive correlation with pH, Ca2+, SO42−, PO43−, and HCO3− mainly in waters with elevated As concentration (>10 ppb) (Table 5). This is a good indication of the same source. Furthermore, in the Durov diagram, the values of the cations and the anions are plotted in the appropriate triangle and projected into the square of the main field, which displays some possible geochemical processes that could affect the water genesis. Figure 3b shows the results of the Durov diagrams, which represent a simple dissolution and mixing fields. This simple dissolution and mixing line support the proposed explanation for Piper classification for the water samples. Arsenic geochemistry and behavior Arsenic concentration in the water samples ranges from 1.70 to 175.0 ppb (Table 3) and exhibits a north-south increasing
Arab J Geosci
Fig. 5 a, b, c Correlation of As versus a PO43− and b Ca2+, and c PO43− versus Ca2+
trend (Fig. 4), with an average of 20.16 ppb, which is higher than the 10.0 ppb safe limit recommended by the JISM (2008) and World health Organization (WHO 2011). Arsenic concentrations showed variation among the wells in different areas, where 87 of the samples are above this maximum permissible limit, while the rest of the investigated wells have low As concentration. The average total As concentrations in the groundwater of the 10 studied localities ranges from 9.05 to 31.56 ppb (Table 4) exceeding thus the JISM and WHO maximum permissible limit. These high averages of As concentrations can be attributed to several mechanisms that govern the As concentration in this aquifer. To understand these mechanisms, 20 rock samples containing phosphate from contaminated localities were analyzed for their major and trace elements (Table 6). Arsenic content ranges between 20 and 27 ppm. The high significant correlation of As with PO43− (R2 =0.84) (Fig. 5a) and Ca2+ (R2 =0.78)
(Fig. 5b) in the water samples support the idea that they came from the same origin. This clearly indicates the association of As with the P and Ca in the phosphorite, most probably substituting P in the apatite structure. Ca was found to correlate positively with PO43− (R2 =0.80) (Fig. 5c). On the other hand, the positive relationship between Ca and As (Fig. 5c) is possibly due to the dissolution of apatite (francolite) (carbonate fluorapatite) where appreciable amounts of As are dissolving, which might reflect rock/water interaction increasing in the direction of groundwater flow. In the studied areas, the presence of francolite was confirmed by SEM (Fig. 6). Moreover, pyrite was present as framboids generally less than 10 μm in the oil shale samples, which were collected from the Muwaqqar Formation overlying the aquifer. The SES analysis showed that substantial As concentrations were present in phosphate and pyrite (Figs. 6 and 7). The substitution of As for P has already been evidenced by many authors, e.g.,
Arab J Geosci
Fig. 6 Scanning electron micrographs of phosphate
Arab J Geosci
Fig. 7 Scanning electron micrographs of framboidal pyrite in oil
Hughes and Drexler (1991), Lazareva and Pichler (2007), and Li et al. (2002).
In literature, it was hypothesized that desorption might also be responsible for the variation in As concentration among
Arab J Geosci
Fig. 8 Thermodynamic stability fields for the different locations
these areas. The highest average concentration of As is detected in Hasa area, which is characterized by high values of phosphate, sulfate, and boron. Kouras et al. 2007 recorded a positive relationship between As and boron in groundwater. Negatively charged ions such as phosphate and sulfate potentially compete with As for adsorption sites. In this study, most attention has been given to phosphate, which certainly affects the behavior of As as indicated by a high positive correlation (Fig. 5a). Despite their opposed toxic and life-supporting natures, the chemistries of arsenate and phosphate have much in common. Both arsenate As (V) and arsenite As (III) desorption are pH-dependent. Phosphate also influences As adsorption onto ferrihydrite, depending on its oxidation state: Phosphate reduces As (III) adsorption at low pH, (Jain and Loeppert 2000) and decreases adsorption of As (V) at high pH (Jain and Loeppert 2000). However, these experiments were conducted at much higher concentrations than are normal in nature, and so, the effect will be small in most practical situations. Dixit and Hering (2003) also showed that, in the presence of phosphate, As (V) and As (III) sorption onto amorphous and crystalline Fe compound is almost the same
over the pH range of 4–10. Phosphate has similar effects on adsorption by both goethite and ferrihydrite (Manning and Goldberg 1996). It is possible that high phosphate concentrations might reduce the adsorption of As (V) in alkaline-oxic waters but have only a small effect in near-neutral reducing waters. Therefore, competition for sorption sites by phosphate appear to sustain elevated aqueous As levels in the upper aquifer. Furthermore, past or ongoing reductive dissolution of Fe3+ oxyhydroxides acts synergistically with competitive sorption to maintain elevated dissolved As levels in the lower aquifer (Swartz et al. 2004). Reducing conditions in some wells may result in the mobilization and release of As from many types of solids (Welch et al. 2000; Nickson et al. 2000), while under oxidizing conditions in the wells, As may adsorb onto Fe oxides, sulfide minerals, and organic matter in groundwater (Welch et al. 2000; Kim et al. 2000). Arsenic concentrations were plotted on an Eh-pH diagram (Fig. 8) using the Geochemist’s Workbench 6.0. They fall in three stability fields. The falling of our samples in three redox phases suggests that both oxic and suboxic conditions predominate in the unconfined portion
Arab J Geosci Table 7 The calculated saturation index of the different mineral phases in the aquifer Parameter
SI anhydrite SI aragonite SI calcite SI dolomite SI gypsum SI celestite SI barite SI anglesite SI cerussite SI halite SI hematite SI hydroxyapatite SI magnesite SI pyrolusite SI rhodochrosite SI siderite SI smithsonite SI strontianite SI goethite
Minimum
Maximum
Mean
Standard deviation
−2.71 −0.910 −0.770 −1.500 −2.510 −4.490 −3.160 −8.870 −3.060
0.300 2.780 2.920 5.690 0.490 −1.080 0.430 −2.950 −1.270
−1.918 0.353 0.495 1.045 −1.708 −2.016 −0.115 −5.668 −2.328
0.425 0.450 0.540 1.036 0.425 0.595 0.600 0.771 0.391
−9.460 13.480 −17.900 −8.360 −13.370 −9.100 −3.040 −3.480 −3.48 5.730
−5.520 21.970 1.950 −3.640 12.390 1.860 1.860 0.540 0.54 9.980
−6.457 17.090 −2.716 −7.075 −11.036 −1.673 −1.673 −0.822 −0.822 7.524
0.833 1.535 3.166 1.064 4.016 1.488 1.488 0.846 0.846 0.773
sorbed to the residual or partially reduced metal (hydr)oxides (McArthur et al. 2004), and cycles of reduction and reoxidation of Fe and S species can cause preferential immobilization of As (Zheng et al. 2004). Arsenic in the present study is also not correlated with Mn, in contrast to previous studies (Ahmed et al. 2004). This lack of correlation suggests that no single mechanism (such as reductive dissolution or pHdependent desorption) can explain As mobilization in the study area. Violante and Pigna (2002) showed how phosphate variably reduces the adsorption of arsenate (but not arsenite) on a variety of oxides, clays, and soils in the pH range of 4–8. Most tested minerals adsorbed similar quantities of arsenate and phosphate; however, Fe, Mn, and Ti oxides and Fe-rich clay minerals (such as smectite and nontronite) retained arsenate more strongly than phosphate. On the other hand, Al-rich minerals such as gibbsite, boehmite, amorphous Al hydroxide, and the clay minerals allophane, kaolinite, and halloysite retained phosphate more strongly than arsenate. Al Kuisi and Abdel-Fattah (2010) reported that the deterioration of soil and groundwater quality is a result mainly of Se–As fertilizers use due to excessive P application, overdosing of soil with phosphate, and undesirable additions of selenium and arsenic in P fertilizers. Statistical analysis
of the aquifer, whereas suboxic conditions predominate along the middle reaches of the flow path, and anoxic/sulfidic conditions predominate in the most down-gradient portions of the aquifer. The significant result encountered is that As was found to be saturated with respect to aragonite, calcite, dolomite, hematite, and goethite but under-saturated with respect to anhydrite, gypsum, celestite, barite, anglesite, cerussite, halite, hydroxyapatite, magnesite, pyrolusite, rhodochrosite, siderite, smithsonite, and strontianite (Table 7). By linking, the results of As concentrations and the results derived from the geochemical model illustrated the high As concentrations indicating that As in the groundwater is influenced by natural sources like the presence of phosphate and oil shale in the geological units above the aquifer. According to van Geen et al. (2004), reductive dissolution and mobilization of As(III) can also occur in less reducing environments or even oxic environments. Anaerobic metalreducing bacteria could play a catalytic role in mobilization of As from basin sediments (Islam et al. 2004). Several studies showed a moderate to strong correlation between As and Fe, as expected from reductive dissolution of FeOOH with adsorbed 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 As and Fe may not be simultaneous. Also, some of the As released by reductive dissolution of (Fe/Mn)–OOH can be re-
The relationships between As, Fe, and SO4 constituents are shown in Fig. 9. This figure shows that there is a significant positive correlation between As and Fe (0.46), and As and SO4 (0.56). R-mode factor analysis was applied to investigate the interrelationships between the analyzed elements and parameters. The analyzed data sets were grouped into a few factors describing variability of the tested elements and parameters. Three factors were extracted from the analyzed elements and parameters, and they accounted for 82.5 % of the total variance in this data set. Parameters with marked loading (more than 0.5) were taken into considerations for factor analyses. 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 listed below: Factor 1: Named rock/water interaction factor and 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, and PO4. On the other hand, correlations between oblique factors (clusters of variables with unique loadings) were performed for these factors and are presented in Fig. 10, which is a
Arab J Geosci Fig. 9 Bivariate relationship of As versus a Fe and b SO42−
pictorial representation of the variables influenced by factors 1, 2, and 3. Factor 1: rock/water interaction factor This factor has high loading on electrical conductivity and most of the major analyzed 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 represent the clays in the aquifer rocks, while Ca, Mg, and Sr belong to the carbonates and phosphorites. Sodium and SO42− are known to substitute for Ca2+ and PO43−, respectively, in the francolite (carbonate fluorapatite) structure. Therefore, this factor represents the interaction between the groundwater and the rocks of the aquifer. Any increase in the concentration
Arab J Geosci Table 8 Factors for hierarchical analysis and loadings of the analyzed elements and parameters Parameter EC (μS/cm) pH Eh (mV) Temp (°C) As (ppb) B (ppb) Ba (ppb) Br (ppb) Ca (ppm) Cd (ppb) Ce (ppb) Cl (ppm) Cr (ppb) Cu (ppb) Fe (ppb) HCO3− (ppm) K (ppm) Li (ppb) Mg (ppm) Mn (ppb) Na (ppm) NO3− (ppm) PO4−3 (ppb) Pb (ppb) Rb (ppb) SO4−2 (ppm) Se (ppb) Si (ppm) Sr (ppm) U (ppb) V (ppb) Eigenvalue % total Cumulative
Factor 1
Factor 2
Factor 3
0.896
0.829 0.910 0.590 0.890 0.615 0.884
0.680 0.740 0.949
Factor 3: phosphate factor This factor is loaded with As, Ce, and PO43−and solves 17.08 of the total variability in the data set (Table. 8). This is a straightforward factor because Ca and PO4 are the major constituents of the francolite crystal structure. Cerium and most rare earth elements are known to substitute for Ca in the francolite structure (McArthur 1985; Abed and Abu Murrey 1997). Li et al. (2002) and Hughes and Drexler (1991) report the substitution of As for P. In this study, As most likely substituted P in the crystal structure of francolite, as indicated by the high significant positive correlation with PO43− discussed previously and shown in Table 5 (Lazareva and Pichler 2007). It seems that these four elements were liberated from the phosphates to the groundwater of the aquifer proportionally. However, the significant positive correlation between As and PO43− can be accounted for by suitable Eh-pH values that keep both ions dissolved in the water of the studied aquifer (Abed et al. 2008; Abed and Sadaqah 2012; Brookings 1988).
Conclusions
0.864 0.632 0.873 0.725 0.935 0.531 0.728 0.877
7.36 35.12 35.12
through the interaction with the rock material in a similar manner as those of factor 1. This explains the significant correlation between the two factors (Fig. 10).
0.789 0.763 3.45 19.12 54.24
2.24 17.08 71.32
of these variables will increase the electrical conductivity due to the dissolution of aquifer matrix or due to the addition of other sources (irrigation return flow or overexploitation of the aquifer).Factor 2: sorption factor This factor is loaded with pH, 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 likely adsorbed on the clay minerals and/or the organic matter of the aquifer rocks. However, some of these elements such as U and V are known, at least partially, to substitute for Ca in the francolite structure (Moh’d and Powell 2010; Abed and Sadaqah 2012). These metals can be liberated to the aquifer
The main objective of this study is to investigate As occurrences and sources within Amman-Wadi Es Sir Aquifer (B2/ A7) of Jordan. The average total As concentration in the Amman-Wadi Es Sir (B2/A7) aquifer in Jordan exceeded the safe limit designated by the Jordanian drinking water standard, the US EPA, and the WHO. The concentration of As was ≥10 ppb in 87 samples out of 150, with a maximum concentration of 173 ppb. Accordingly, the chronic exposure to such elevated concentrations might inflect serious health problems. The geochemical and statistical treatment of the data revealed the following: 1. The data show that the highest As concentrations are located in the Al Hasa area, which has a heavy mining activity. According to our study, the raw phosphorite samples contained up to 27 mg/kg As, and there was a strong correlation between As, P, and Ca, suggesting that these elements were derived from the same source. Moreover, the SEM images of representative phosphorite and oil shale samples show the association of As with P and Ca, and the EDAX analysis showed that substantial As concentrations were present in phosphate and pyrite. 2. This study suggests that As enrichment in phosphate rock found in the aquifer formation and oil shale samples in the soils above the aquifer accounts for the release of a significant amount of As and transport to the groundwater
Arab J Geosci Fig. 10 3D representation of the factors: salinity, sorption, and phosphate
via formation of arseno-carbonate complexes. Moreover, other mechanisms can be called upon to account for the elevated As concentration in some wells such as the simple dissolution of iron oxyhydroxides. 3. The results of factor analysis indicate that there are three factors that explain about 82.5 % of the variance in the dataset. The analysis clearly shows the association of As with the phosphorite factor. These factors are 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, and PO4. 4. The aquifer has been found to be saturated with aragonite, calcite, dolomite, hematite, and goethite. However, the aquifer was under-saturated with anhydrite, gypsum, celestite, barite, anglesite, cerussite, halite, hydroxyapatite, magnesite, pyrolusite, rhodochrosite, siderite, smithsonite, and strontianite. From geochemical modeling, we observed that there are many minerals constituting oil shale
and phosphate beds such as calcite, quartz, kaolinite, dolomite, gypsum, pyrite, and apatite. Dissolution of these minerals releases considerable As concentration to the groundwater aquifer. 5. Ca2+, Na+, Cl−, and HCO3− are the most dominant ions in the samples. In 87 water samples (58 %), the abundance of the cations is in the following order Ca>Na>Mg>K, while the remaining 42 % of the samples follow the abundance order Na>Ca>Mg>K. On the other hand, anion test results show the abundance orders of HCO3− >Cl− > SO42− >NO3− and Cl− >HCO3− >SO42− >NO3−. However, the cations and anions generally show an increasing trend along groundwater flow path. Using Piper classification reveals that the great majority of groundwater exhibits two hydrochemical facies, Ca–Mg–HCO3 and Na, Ca– SO4, Cl. This means that the chemical composition of the groundwater is affected mainly by recharge water, carbonate-phosphate oil shale minerals dissolution, and some anthropogenic pollution like irrigation return flow. 6. The concentrations of other cations in most of the groundwater samples were below the maximum permissible limits of the JISM and WHO guidelines. Acknowledgments Thanks are due to the anonymous reviewers of this journal for highly improving the manuscript. Thanks and gratitude is also
Arab J Geosci due to the Deanship of Scientific Research at the University of Jordan for supporting and sponsoring this research. This research has been accomplished during the sabbatical leave offered to the senior author from the University of Jordan starting February 2014–January 2015.
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