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Journal of Arid Land  2021, Vol. 13 Issue (4): 350-374    DOI: 10.1007/s40333-021-0055-8
Research article     
Source identification of nitrate in the upper aquifer system of the Wadi Shueib catchment area in Jordan based on stable isotope composition
Mutawakil OBEIDAT1,*(), Muheeb AWAWDEH2, Noor AL-KHARABSHEH3, Ahmad AL-AJLOUNI1
1Faculty of Science and Arts, Jordan University of Science and Technology, Irbid 22110, Jordan
2Laboratory of Applied Geoinformatics, Department of Earth and Environmental Sciences, Yarmouk University, Irbid 21163, Jordan
3Department of Water Resources and Environmental Management, Al-Balqa Applied University, Al-Salt 19117, Jordan
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Groundwater forms the main freshwater supply in arid and semi-arid areas, and contamination of this precious resource is complicated by the slow rate of recharge in these areas. Nitrate contamination of groundwater is a global water quality problem, as it entails threat to human health as well as aquatic ecosystems. Source identification of contamination is the cornerstone and a prerequisite for any effective management program of water quality. Stable isotope composition of the dissolved nitrate (δ15N-NO3- and δ 18O-NO3-) has been applied to identify NO3- sources and the main transformation processes in the upper aquifer system (A1/2, A4, and B2/A7 aquifers) in the Wadi Shueib catchment area, Jordan. Moreover, the stable isotope compositions of the groundwater (δ2H-H2O and δ18O-H2O) in conjunction with the groundwater hydrochemistry were integrated to investigate the origin and evolution of the groundwater. Results revealed that groundwater in the study area is fresh and hard-very hard water, and mainly a Ca-Mg-Cl type. NO3- concentration was in the range of 7.0-74.0 mg/L with an average of 37.0 mg/L. Most of the samples showed concentration higher than the natural background concentration of NO3- (5.0-10.0 mg/L). The δ 2H-H2O and δ18O-H2O values indicated that the groundwater is meteoric, and of Mediterranean origin, with a strong evaporation effect. The δ15N-NO3- values ranged between 6.0‰ and 11.3‰ with an average of 8.7‰, and the δ18O-NO3- values ranged between 1.6‰ and 5.9‰ with an average of 3.4‰. These values are in conformity with the stable isotope composition of nitrate derived the nitrification of wastewater/manure, and soil NH4. Nitrification and denitrification are the main transformation processes affecting nitrogen species. Statistical analysis revealed no significant differences in the δ2H-H2O and δ18O-H2O values, and δ15N-NO3- and δ 18O-NO3- values for the three aquifers (A1/2, A4, and B2/A7), indicating that the groundwater of these aquifers has the same origin, and a common source of pollution.

Key wordsδ15N-NO3-      δ18O-NO3-      nitrate sources      pollution      meteoric origin      aquifer      Jordan     
Received: 23 February 2020      Published: 10 April 2021
Corresponding Authors: Mutawakil OBEIDAT     E-mail:
About author: * Mutawakil OBEIDAT (E-mail:
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Mutawakil OBEIDAT, Muheeb AWAWDEH, Noor AL-KHARABSHEH, Ahmad AL-AJLOUNI. Source identification of nitrate in the upper aquifer system of the Wadi Shueib catchment area in Jordan based on stable isotope composition. Journal of Arid Land, 2021, 13(4): 350-374.

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Fig. 1 Location of the study area in Jordan (a) and distribution of the meteorological stations in the study area (b)
Fig. 2 Geological map of the study area
Hydrogeological unit Aquifer potentiality Thickness (m) Hydraulic conductivity (m/d)
B2/A7 Aquifer 140-265 2
A5/6 Aquitard 50-60 1×10-4
A4 Aquifer 40-65 2
A3 Aquitard 50-80 1×10-4
A1/2 Aquifer 86-200 1
Kurnub Aquifer 150-50 3
Table 1 Hydraulic properties of the hydrogeological system in the study area (Margane et al., 2009)
Fig. 3 Distribution of the land cover in the study area (Jawarneh and Biradar, 2017). Sample locations are also shown.
Parameter Minimum Maximum Mean Maximum permissible concentration recommended by WHO (2011) Standard deviation Coefficient of variation (%)
NO3- (mg/L) 7.1 74.4 37.0 50.0 18.0 47
Cl- (mg/L) 33.0 156.0 87.0 600.0 38.0 43
SO42- (mg/L) 22.0 118.0 51.0 600.0 29.0 57
HCO3- (mg/L) 104.0 180.0 158.0 600.0 17.0 11
Na+ (mg/L) 22.0 81.0 47.0 200.0 22.0 46
K+ (mg/L) 1.0 14.0 4.0 200.0 4.0 107
Mg2+ (mg/L) 12.0 40.0 24.0 500.0 7.0 31
Ca2+ (mg/L) 62.0 137.0 92.0 200.0 18.0 20
EC (μS/cm) 498.0 892.0 687.0 - 140.0 20
TDS (mg/L) 309.0 558.0 428.0 1500.0 90.0 21
pH 6.4 7.1 6.6 8.5 0.2 3
TH (mg/L) 257.0 415.0 326.0 500.0 41.0 13
CAI -0.1 0.4 0.1 - 0.1 1
SI-calcite -0.7 -0.2 -0.4 0.1 30
SI-dolomite -1.8 -0.8 -1.0 0.3 25
SI-gypsum -2.3 -1.3 -1.9 0.3 13
SI-halite -7.7 -6.5 -7.0 0.4 5
δ18O-H2O (‰) -6.3 -4.8 -5.5 0.5 9
δ2H-H2O (‰) -28.7 -20.7 -24.7 2.0 10
δ15N-NO3- (‰) 6.0 11.3 8.7 2.0 20
δ18O-NO3- (‰) 1.6 5.9 3.4 1.0 41
Table 2 Descriptive statistics of the hydrochemical parameters of the groundwater samples
Fig. 4 Spatial distribution of electrical conductivity (EC) (a) and nitrate (NO3-) concentration (b)
Parameter NO3- Cl- SO42- HCO3- Na+ K+ Mg2+ Ca2+ EC pH TH 18O-H2O 2H-H2O 15N-NO3- 18O-NO3-
NO3- 1.0 0.5 0.4 0.0 0.6 0.7 0.0 0.3 0.6 -0.3 0.3 0.7 0.6 0.5 -0.1
Cl- 0.5 1.0 0.7 0.3 1.0 0.6 0.5 0.3 0.9 -0.4 0.7 0.7 0.8 0.7 0.2
SO42- 0.4 0.7 1.0 0.4 0.8 0.7 0.2 0.6 0.9 -0.6 0.8 0.8 0.8 0.7 0.2
HCO3- 0.0 0.3 0.4 1.0 0.3 0.2 0.3 0.3 0.4 -0.1 0.5 0.1 0.1 0.5 0.3
Na+ 0.6 1.0 0.8 0.3 1.0 0.8 0.5 0.3 1.0 -0.4 0.7 0.8 0.9 0.7 0.1
K+ 0.7 0.6 0.7 0.2 0.8 1.0 0.2 0.3 0.7 -0.4 0.5 0.7 0.7 0.5 -0.2
Mg2+ 0.0 0.5 0.2 0.3 0.5 0.2 1.0 -0.5 0.4 -0.2 0.2 0.1 0.1 0.1 0.2
Ca2+ 0.3 0.3 0.6 0.3 0.3 0.3 -0.5 1.0 0.5 -0.4 0.8 0.4 0.4 0.7 0.2
EC 0.6 0.9 0.9 0.4 1.0 0.7 0.4 0.5 1.0 -0.5 0.9 0.8 0.8 0.8 0.2
pH -0.3 -0.4 -0.6 -0.1 -0.4 -0.4 -0.2 -0.4 -0.5 1.0 -0.5 -0.4 -0.4 -0.4 -0.1
TH 0.3 0.7 0.8 0.5 0.7 0.5 0.2 0.8 0.9 -0.5 1.0 0.6 0.5 0.8 0.4
18O-H2O 0.7 0.7 0.8 0.1 0.8 0.7 0.1 0.4 0.8 -0.4 0.6 1.0 1.0 0.6 -0.1
2H-H2O 0.6 0.8 0.8 0.1 0.9 0.7 0.1 0.4 0.8 -0.4 0.5 1.0 1.0 0.6 0.0
15N-NO3- 0.5 0.7 0.7 0.5 0.7 0.5 0.1 0.7 0.8 -0.4 0.8 0.6 0.6 1.0 0.6
18O-NO3- -0.1 0.2 0.2 0.3 0.1 -0.2 0.2 0.2 0.2 -0.1 0.4 -0.1 0.0 0.6 1.0
Table 3 Bivariate statistics of the hydrochemical parameters of the groundwater samples
Fig. 5 Piper diagram of the groundwater samples in the study area. A1/2, Na'ur aquifer; A4, Hummar aquifer; B2/A7, Amman/Wadi Wadi Es Sir aquifer.
Fig. 6 Plots of Cl- vs. Na+/Cl- ratio (a), Cl- vs. HCO3-/Cl- ratio (b), Cl- vs Ca2+/Na+ ratio (c), and Cl- vs. Ca2+/HCO3- ratio (d). The green solid line indicates the molar ratio of calcite dissolution.
Fig. 7 Plots of SI-calcite vs. HCO3- (a), SI-dolomite vs. HCO3- (b), SI-gypsum vs. SO42- (c), and SI-halite vs. Cl- (d). SI-calcite, SI-dolomite, SI-gypsum, and SI-halite represent the saturation indices of calcite, dolomite, gypsum, and halite, respectively.
Fig. 8 Plots of CAI vs. Cl- (a), and (Na++K+)-Cl- vs. (Ca2++Mg2+)-(SO42-+HCO3-) (b). The black solid line separates the two types of ion exchange (reverse ion exchange and base ion exchange).
Fig. 9 Plot of δ18O-VSMOW vs. δ2H-VSMOW values of the groundwater samples. VSMOW, Vienna Standard Mean Ocean Water; MMWL, the Eastern Mediterranean Meteoric Water Line; LMWL, the Local Meteoric Water Line; LEL, the local evaporation line; GMWL, the Global Meteoric Water Line.
Fig. 10 Plots of δ18O-VSMOW vs. Cl- (a) and δ18O-VSMOW vs. deuterium excess (d-parameter) (b)
Fig. 11 Plot of δ15N-atmospheric air vs. δ18O-VSMOW of the groundwater samples in the study area. The stable isotopic composition of nitrate in wastewater in the study area is also presented.
Fig. 12 Plots of δ15N-atmospheric air vs. Cl- (a), δ15N-atmospheric air vs. δ18O-VSMOW (b), and δ15N-atmospheric air vs. NO3- (c). The regression line and correlation coefficient are also presented.
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