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Review

δ34S, δ18O, and δ2H-δ18O as an Approach for Settling the Question of Groundwater Salinization in Neogene Basins: The North of Morocco in Focus

1
Polydisciplinary Faculty of Nador, Géo-Environnement et Santé, Mohamed I University, Oujda, LCM2E Lab BP 300, Selouane 62702, Morocco
2
Geology & Sustainable Mining Institute (GSMI), Mohamed VI Polytechnic University, Ben Guerir 43150, Morocco
3
Center for Remote Sensing Applications (CRSA), Mohamed VI Polytechnic University, Ben Guerir 43150, Morocco
4
Mohamed VI Museum for the Civilization of Water in Morocco, Ministry of Habous and Islamic Affairs, Marrakesh 40000, Morocco
5
GEE, Laboratory of Applied Sciences (LSA), ENSAH, Abdelmalek Essaadi University, Al Hociema 32003, Morocco
6
Earth Sciences Faculty, University of Barcelona, Marti i Franquès, s/n, 08028 Barcelona, Spain
7
Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70802, USA
*
Author to whom correspondence should be addressed.
Water 2022, 14(21), 3404; https://doi.org/10.3390/w14213404
Received: 24 September 2022 / Revised: 20 October 2022 / Accepted: 24 October 2022 / Published: 27 October 2022

Abstract

:
Neogene plains around the Mediterranean basin are characterized by considerable groundwater salinization. Some studies have misidentified seawater intrusion as the main source of salinity. Across northern Morocco, we gathered δ18OSO4 and δ34SSO4 data from coastal and inland aquifers, Messinian marls, and volcanic products. Differences in the isotopic composition between Messinian marls and some groundwater in all aquifer samples indicate that salinization in groundwater is a consequence of dissolution of Messinian evaporite deposits; nevertheless, modern agriculture and wastewater strongly influence depletion in levels of δ34SSO4. Our novel approach enables effective investigation of processes governing salinity in Neogene basins to support more informed water resource management and governance.

1. Introduction

The perimeter of the Mediterranean basin has played a key role in cultural exchanges between its inhabitants in both east-to-west and north-to-south directions. Thanks to its history and favorable climate, the Mediterranean basin has seen and continues to experience a steady and significant population growth, strong urbanization, and increases in the level of groundwater consumption. In particular, Morocco, because of its geographic situation, has been considered to be a migration hub between dry northern Africa and the more humid central and northern Europe. Presently, Morocco handles and struggles with large increases in water demand. In this context, the Moroccan government has been engaged in a dynamic policy on water resource management and governance to provide the country with important hydraulic infrastructure, improve access to drinking water, and develop smart irrigation. In fact, groundwater is not just a prerequisite for life, but also an essential element for socioeconomic development. Groundwater quality and quantity in Morocco are directly impacted by human development [1], climate change [2], and the local geological environment [3]. These impacts have been noticed in the behavior and response of aquifers to reduced precipitation, increased groundwater pumping [4], and pollution [5,6]. The sources of groundwater salinity in Morocco include seawater intrusion [7], dissolution of evaporites in Neogene basins [8], Triassic sediments [9], and agricultural irrigation [10]. This paper reviews the current state of isotope analyses which combine the most novel isotopic signatures in groundwater, with their interpretation in terms of Messinian-aged marls and volcanic products. The latter contain ancient and unique isotopic sulfur compositions and thus serve to assess the possible sources of sulfate ions in groundwater. We chose to analyze Messinian marls and volcanic pyroclastic rocks because marls commonly form the substratum of the aquifers in northern Morocco, and during the Messinian period explosive volcanic eruptions were widespread. This volcanic activity appears in the form of many pyroclastic flows and cinerites within the sedimentary series. Although most Messinian evaporite deposits have been eroded, and it is difficult to find suitable outcrops for sampling, we consider that Messinian volcanism may have affected the geochemical composition of similar-aged sediments as well as marls.
In this paper, we use isotopic and geological analyses to suggest a novel interpretation for the origin of groundwater salinization. Based on prior hydrochemical studies in these areas, two working hypotheses have been proposed. The first suggests that there is a likely mixing of freshwater with seawater in coastal aquifers [6,10], and the second interprets an enrichment of groundwater by Cl, Na+, SO42−, Ca2+ and Mg2+ [11] from geological sources. Our objective is to address some critical questions concerning groundwater salinity in northern Morocco: (1) Do sediments dating from the Messinian Salinity Crisis (MSC; from 5.96 to 5.33) play a role in triggering the mineralization of groundwater, or (2) is groundwater mineralization caused by saltwater intrusion from the Mediterranean Sea? In this regard, we describe the geochemical features which characterize groundwater in Neogene basins in northern Morocco and establish how the stratigraphic record of the MSC relates to the different proposed groundwater salinization scenarios across the whole Mediterranean basin perimeter? To help answer these questions, (1) we present a geological synthesis of MSC in the Mediterranean basin, (2) hydrogeochemical and isotopic analyses of groundwater samples whose origin of mineralization is in question and (3) perform a comparison of isotopic data collected from the Ghis-Nekor, BouAreg-Gareb and Kert aquifers in northern Morocco, whose mineralization comes exclusively from interaction with Messinian marls, cinerites and a mixture of marls cinerites deposits.

2. Regional Geology

Between the Tortonian and the Holocene, the geological history of the Moroccan Rif area (Figure 1) was dominated by the tectono-sedimentary evolution of the Riffian belt, controlled by both the westward motion of the Alboran microplate and the northward displacement of Africa with respect to Europe [12]. The Rif Mountains area resulted from complex nappe sequences from that period. From the Upper Miocene (Messinian) until the Quaternary [13], intra mountainous basins continued to develop and deform. However, the distinct event that marked the region during this period was the Messinian Salinity Crisis (MSC). The MSC corresponds to the break of connection between the Atlantic Ocean and the Mediterranean Sea, causing the desiccation of the Mediterranean Sea [14]. Consequently, thick evaporitic units were deposited in the Mediterranean [15], as well as in the marginal basins [16]. Marginal and deep basin evaporites are chronologically disconnected by as much as 260 kyr [17]. That is because the Mediterranean Sea and Atlantic Ocean probably continued to be partially connected via Riffian and Betic Corridors in the north of Morocco and in the south of Spain, respectively. Until recently, two principal causes of the MSC were proposed, including a break in communication between the Atlantic and the Mediterranean Sea caused by plate tectonics [18,19], combined with global climatic and eustatic changes [20,21]. The absolute age of the MSC is still a cause of geological debate. There is general common agreement on the age of the start of the salinity crisis (5.96 Ma) and its end at 5.33 Ma [22], with duration of 0.63 Ma. Nonetheless, some still suggest that the MSC began at about 5.7 Ma, and ended at about 5.3 Ma; with duration of about 0.4 Ma [23].

2.1. Local Geology and Hydrogeology

2.1.1. Ghis-Nekor Plain

The Ghis-Nekor Plain of the Al Hoceima region is located between the Internal and External Zones of the Rif Mountains Volcanic rocks of the Tortonian–Messinian outcrop in Ras Tarf, east of Al Hoceima [25] and Neogene Plio-Quaternary sediments are confined to the Ghis-Nekor basin. This latter is bounded by Bousekkour–Aghbal and Trougout onshore faults, extending offshore to the Mediterranean Sea. The Bokkoya fault (Figure 2a,b) is a major eastward dipping fault that bounds the western Al Hoceima Bay [26]. The Trougout fault represents the active eastern major fault of the Nekor strike–slip related basin, while the Bousekkour–Aghbal and Bokkoya faults were recently active along its diffuse western boundary. Between these structures, small fault-bounded sub-basins connect at depth to a steep WSW dipping master fault, all together forming a large-scale transtensional basin with an interpreted “flower structure” at depth (Figure 2b) [26]. Previous studies [10] show that transmissivity in the Ghis-Nekor aquifer varies between 8.8 × 10−4 m2s−1 and 6.5 × 10−2 m2s−1. The maximum values are observed around the Nekor and Ghis Rivers, while the lowest values are located in the eastern part, ranging between 3.75 and 0.6 × 10−3 m2s−1. The permeability values vary in the range of 10−3 to 3 × 10−6 ms−1. In fact, the majority of the aquifer is characterized by permeability values higher than 0.1 × 10−3 ms−1, while the lowest values are observed in the eastern plain where hydraulic permeability is less than 0.001 × 10−3 ms−1.

2.1.2. BouAreg-Gareb Plain

The BouAreg-Gareb study area is located within the Neogene basin of the Melilla-Nador region, where there are two aquifers. The coastal aquifer lies beneath the BouAreg plain and the continental one beneath the Gareb plain. These two aquifers are hydrogeologicaly connected across the Selouane passage (Figure 3). From a combined hydrogeological point of view, the BouAreg and Gareb aquifers cover an area of about 480 km2. The aquifers lie within Plio-Quaternary deposits and are bounded at their base by a Neogene substratum of marls. The aquifers have good hydrodynamic characteristics [30], mainly associated with high permeability (7 × 10−4 ms−1) in the vicinity of the lagoon (Sebkha)to the west, while the lowest values are found at the borders of the Kebdana massif. Transmissivity varies continuously from upstream (9 × 10−4 m2s−1) to the coastal zone (2 × 10−2 m2s−1). The highest values for transmissivity are found in the west, whereas the lowest are measured at the borders of the Kebdana massif, probably due to the accumulation of marls. All along the coast, the transmissivity ranges around 2 × 10−2 m2s−1 [31].

2.1.3. Kert Plain

The Kert basin, which covers a total area of about 250 km2, is located in northeastern Morocco (Figure 4A). During the Miocene to Villafranchian, the Kert depression received mixed and varied thick marine and continental sediments. We consider that the Miocene deposits contain gypsum as can be seen in some outcrops of the region. At its top, the series ends with gravels, silts, and clays from the Villafranchian age. The Plain of Kert (Figure 4) is limited to the east by the western Gareb range. The metamorphic massif of Temsamane which limits the plain in the north and northwest was affected by a compressive tectonic event generating a N120°E fracture cleavage associated with green schists [32]. The southern portion of the basin contains Intra-Riffain nappes and Miocene marls. Further south, the plain is surrounded by mostly Jurassic and Cretaceous carbonates rocks. The strata of key hydrogeological formations can be identified (Figure 4B). The substratum of the aquifer is represented by Upper Miocene transgressive marls, which are overlain by the Plio-Quaternary deposits comprising limestones and conglomerates.

3. Materials and Methods

For our research, the δ2H and δ18O of water were obtained by H2 and CO2 equilibrium, respectively, and isotope ratio mass spectrometry (IRMS) was conducted with a Delta-S Finnigan Mat Mass Spectrometer. For S and O isotope analysis, the dissolved SO4 was precipitated as BaSO4 by the addition of BaCl22H2O, after acidifying the sample with HCl and boiling it to prevent Ba(CO3) precipitation. The S isotopic composition was determined with an Elemental Analyzer (Carlo Erba 1108) coupled with an IRMS (Delta-C Finnigan Mat). The O isotopic composition was analyzed with a thermo-chemical elemental analyzer (TC/EA Thermo-Quest Finnigan) coupled with an IRMS (Delta-C Finnigan Mat). Notation is expressed in terms of δ% relative to Vienna Standard Mean Ocean Water (V-SMOW) and Vienna Cañón Diablo Troilite (V-CDT) standards. The isotope ratios were calculated using international and internal laboratory standards. The reproducibility of the samples calculated from standards systematically interspersed in the analytical batches is ±0.5% for δ2H, ±0.2% for δ18OH2O, ±0.2% for δ34S, and ±0.5% for δ18OSO4. All water samples for isotopic analyses were prepared and analyzed at the Scientific-Technical Services of the University of Barcelona. Isotopes of Messinian marls and volcanic deposits were prepared and analyzed at the Oxy-Anion Stable Isotope Consortium of the Louisiana State University.

4. Results and Discussion

4.1. δ18O and δ2H

Isotopic analyses (δ18O and δ2H) were conducted on groundwater samples collected from productive wells and rivers. The distribution of the well and river samples is given in Figure 5, and the isotopic analyses of these samples are presented in Table 1. The δ18O and δ2H collected from the Ghis-Nekor aquifer vary from −5.37‰ to −4.15‰ and from −41.7‰ to −28.4‰ respectively. Nearly all sample data plot below the Global Meteoric Water Line (GMWL) [35] (Figure 5). This river’s water isotopic contents are 6.2‰ for δ18O and 40.5‰ for δ2H and plot almost on the GMWL. Notably, we interpret that sample analyses from Ghis-Nekor aquifer plot along two evaporation lines. The first sample, taken from a well at the eastern edge of the aquifer and with a source whose composition (δ2H: 34.40‰; δ18O: −5.63‰) is marked by the intersection of the (upper) evaporation line and the GWML. The second evaporation line (from the west) connects relatively freshwater sample data of the Ghis River whose signature is more depleted in heavy isotopes. Samples taken from wells located progressively further north samples show greater enrichment in heavy isotopes. Between these two evaporation lines lie data taken from samples in intermediate wells, corresponding to cases of mixed groundwater.
In the BouAreg-Gareb aquifer, δ18O and δ2H compositions of groundwater range from −6.1‰ to −5.2‰ and from −40.2‰ to −30.4‰, respectively. All sample data plot either under or along the GMWL. This suggested that enrichment in heavy isotopes is typical for water that has been subjected to evaporation. If we consider the point of intersection between sample values and the GMWL, the inferred isotopic composition would be the source of recharge. This point has values of δ2H: −37.6‰ and δ18O: −6.08‰ and comes from a sample located near the Kebdana Mountains.
In the Kert aquifer the δ18O and δ2H compositions of groundwater range from −5.74 to −4.51‰ and from −40.8‰ to −34.1‰, respectively. The surface water sample taken from the Kert River has values of -6.47‰ for δ18O, and −47.6‰ for δ2H. These values are more depleted in heavy isotopes compared to the groundwater, suggesting a high-altitude recharge. All the water well samples plot along an evaporation line (Figure 5) with an interpreted source whose composition (δ2H: −36.1‰; δ18O: −5.74‰) is given by the intersection of the evaporation line and the GMWL. A diffusion process could potentially exist between groundwater and Kert River (Figure 5).
Without absolute age dates it is difficult to estimate the recharge age of groundwater in the area studies. Nevertheless, the high concentration of NO-3 (Table 1) in the groundwater can be attributed to present-day anthropogenic sources mainly from agriculture, animal manure and wastewater.
We note that both interior and coastal aquifers have a similar isotopic composition. Based on geographical position of wells and the intersection of the evaporation line with the GMWL, we suggest that aquifers are being recharged by runoff (Kert aquifer) and groundwater flow from the RasTraf (Ghis-Nekor aquifer) and Kebdana/Aroui Mountains (BouAreg-Gareb aquifer). All the data from groundwater samples show relatively low slopes, less than 8 (Table 1), although according to the conventional interpretation, this result may reflect slight and variable degrees of evaporation during or after rainfall infiltration under different climatic conditions. The low slopes indicate that the evaporation mechanism is not sufficient to explain the increasing salinity in all aquifers. In the following section, we use sulfur and oxygen isotopes of sulfate to resolve the question of groundwater salinity.

4.2. δ18OSO4 and δ18OH2O

For the Ghis-Nekor study area, isotopic measurements were performed on 20 groundwater samples from aquifer wells and a surface water sample from the Ghis River. The δ18O isotopic content in sulfates (SO4) varies between +4.35‰ and +8.60‰, while the isotopic signature of δ18O in SO4 from the Ghis river SO4 is +4.95‰. In the BouAreg-Gareb study area, isotopic measurements were carried out on 29 well samples and one sample from the Al-Arouit spring. The oxygen isotope data for sulfates (δ18OSO4) in water samples range from +4.75‰ to +11.48‰, and is +8.4‰ in the Al-Arouit spring. The oxygen isotope data for sulfates (δ18OSO4) extracted from 14 water samples collected in the Kert aquifer vary from +5.02‰ to +13.86‰, and is+5.3‰ in Kert River (Table 1).
We suggest that the dominant control of δ18O of in the groundwater comes from mixing with dissolved sulfate sediment, i.e., precipitated gypsum or anhydrite. Our data indicate that the δ18OSO4 values may be a function of the sulfate sources and not the water composition because otherwise, sulfates formed via sulfide oxidation would show a good correlation between δ18OSO4 and δ18OH2O, which is not observed (Figure 6). A key attribute of sulfate ions is that they do not exchange oxygen with the surrounding groundwater [36] and our sample values plot on a trend distinct from those of atmospheric O2. If either the groundwater or atmosphere had exerted a strong isotopic influence, the isotope sulfate data values would trend along or near either the 1:1 line or the atmospheric O2 line (Figure 6), which they do not.
Similar to the Neogene basins in southern Spain, our data also show that the original seawater from which gypsum/anhydrite precipitated is also considerably lighter than regular seawater 8.6‰ [37]. Most of our sulfate samples show δ18O values different to that expected for modern marine sulfates (8.6‰) or volcanic products (3.99‰), although the plotted sample values show a trend (Figure 6) toward that of volcanic products, indicating their geochemical influence. Together, δ18O values and their trends taken from sulfate ions indicate that that during the precipitation of evaporites in the Messinian the marginal basins were receiving an input of continental water influenced by volcanic products.

4.3. δ34SSO4 and δ18OSO4

Messinian marls and marls-volcanic deposits (δ34S = 18.3‰, δ18OH2O = 6.43‰, 34S = 17.6‰, δ18OH2O = 6.56‰) show no similar isotopic composition to actual seawater (34S ≈ 20‰, δ18OH2O ≈ 9.5‰). Our data indicate that low values of δ34S and δ18OH2O in our Neogene basins are controlled mainly by continental water [39] or an additional supply of Triassic sulfates [40]. In our case (Figure 7), the decrease of isotopic values also implies that during the Messinian, marginal basins in the north of Morocco were isolated from Mediterranean Sea, or at least with a limited connection. Consequently, they were more influenced by continental waters enriched with light isotopes. Plotted δ34S values from groundwater samples show no consistent relationship to the high concentration of SO4, δ18O (Table 1) or the distance from the sea. However, the downward shift of δ34S values to values below that of Messinian marls (EM: Figure 7) may be a consequence of some contamination. Considering the high concentrations measured for NO3 in groundwater, all aquifers are expected to show depletion in δ34S. The responsible anthropogenic contamination from animal manure concomitantly supplies sulfates rich in light sulfur. In addition, volcanic products can contribute light sulfur isotopes (EM1: Figure 7), with a value of δ34S: 6.8‰ and so decrease the value of this isotopic signal. Furthermore, surface water (EM2: Figure 7) plays an important role in changing the isotopic signature. In general, sulfates of non-gypsiferous origin dissolved either in surface water or, altered by volcanic products, are depleted in heavy isotopes. Based on the high amount of SO4, we assume that although groundwater does not conserve the Messinian marls’s (EM) isotopic signal, the salinity was originally derived from dissolution of gypsum concealed in Messinian marls. However, the change from the initial (EM) to final state is controlled by river water, agriculture, and volcanic products. This change, in contrast, relates only to the isotopic signal, and not to the salinity. The sulfate sources identified in this study is similar to those found in southern Spain [41].

5. Conclusions

Interpretations of δ34S and δ18O values measured in groundwater samples indicate a dominant role of dissolved Messinian evaporites in the history of groundwater and argue against marine saltwater contamination of the groundwater. However, the primary seawater isotopic signature of evaporites deposited during the MSC, is affected by isotopic contributions from continental waters and volcanic products during the Neogene. Additionally, the differences observed in the isotopic composition between Messinian marls and groundwater in all aquifer samples, supports the hypothesis that salinization in groundwater is a consequence of contributions from MSC evaporites. The δ18O and δ2H isotope data obtained in this study show that for water samples from wells, their values do not generally lie along the GMWL and demonstrates that rapid isotopic enrichment can occur as a result of evaporation in this arid setting. Considering the high concentration of NO3, actually, groundwaters in all aquifers undergo depletion due to anthropogenic sources, mainly agriculture and wastewater. Future geological and isotopic research would help further establish this proposed origin for groundwater salinization.

Author Contributions

Conceptualization, M.E. (Mohammed Elgettafi) and J.M.L.; methodology, M.E. (Mohammed Elgettafi) and M.H.; software, M.E. (Malak Elmeknassi); validation, A.C., A.E. and M.H.; investigation, M.E. (Mohammed Elgettafi), M.E. (Malak Elmeknassi) and A.E.; data curation, M.E. (Mohammed Elgettafi); writing original draft preparation, M.E. (Mohammed Elgettafi); writing—review and editing, J.M.L.; visualization, A.E. and M.H.; supervision, A.C. All authors have read and agreed to the published version of the manuscript.

Funding

This research received an external funding from the Spanish Agency of International Cooperation for the Development (AECID): Project CGL2009-07025.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available to readers without any request from the corresponding author.

Acknowledgments

The present work is granted by the Spanish Agency of International Cooperation for the Development (AECID). The project has been funded by the Spanish Ministry of Science and Innovation through the project CGL2009-07025. The authors greatly appreciate the analytical support of the Scientific-Technical Services of the University of Barcelona and H. Bao at Louisiana State University.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Geological map of Rif ranges and Neogene basins [24].
Figure 1. Geological map of Rif ranges and Neogene basins [24].
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Figure 2. Geological map of the Al Hoceima region (a) [27,28,29]. E–W structural cross-section AA′ (b) [26].
Figure 2. Geological map of the Al Hoceima region (a) [27,28,29]. E–W structural cross-section AA′ (b) [26].
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Figure 3. Geological map of the BouAreg and Gareb plains.
Figure 3. Geological map of the BouAreg and Gareb plains.
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Figure 4. Geological sketch (A) and Hydrogeological cross-section of the Kert Plain(B) [33]. (modified from [34].
Figure 4. Geological sketch (A) and Hydrogeological cross-section of the Kert Plain(B) [33]. (modified from [34].
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Figure 5. Isotope δ2H–δ18O compositions of the groundwater in the study areas.
Figure 5. Isotope δ2H–δ18O compositions of the groundwater in the study areas.
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Figure 6. Oxygen isotope compositions of the dissolved sulfate species (δ18OSO4 versus) relative to those of groundwater (δ18OH2O) from which the sulfate was extracted seawater data from [37], O-O line from [38].
Figure 6. Oxygen isotope compositions of the dissolved sulfate species (δ18OSO4 versus) relative to those of groundwater (δ18OH2O) from which the sulfate was extracted seawater data from [37], O-O line from [38].
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Figure 7. Cross-plot of δ34S versus δ18OSO4 of groundwater, Messinian marls, cinerite, volcano-sedimentary rocks, and Messinian gypsum are from Grenade and Lorca [42] and Triassic sulfates from Apennines Italy [43], EM-Messinian marls, EM1-volcanic products, EM2-surface waters.
Figure 7. Cross-plot of δ34S versus δ18OSO4 of groundwater, Messinian marls, cinerite, volcano-sedimentary rocks, and Messinian gypsum are from Grenade and Lorca [42] and Triassic sulfates from Apennines Italy [43], EM-Messinian marls, EM1-volcanic products, EM2-surface waters.
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Table 1. Isotopes analysis (δ18O, δ2H and δ34SSO4 and δ18OSO4), chemical analysis (sodium, chloride, sulfate, and nitrate) and electrical conductivity. S: Spring, R: Well near manure, GR: Ghis River, KR: Kert River, MM: Messinian Marls, C: Cinerite and VMD: volcanic marls deposits.
Table 1. Isotopes analysis (δ18O, δ2H and δ34SSO4 and δ18OSO4), chemical analysis (sodium, chloride, sulfate, and nitrate) and electrical conductivity. S: Spring, R: Well near manure, GR: Ghis River, KR: Kert River, MM: Messinian Marls, C: Cinerite and VMD: volcanic marls deposits.
IDECNa+ClSO4NO3δ18OH2Oδ2Hδ18OSO4δ34SSlope
µS/cmmg/L
B120104318021026−6.08−37.55.7515.57.81
B23840851138534235−5.38−37.29.2414.98.78
B462101507249032414−5.29−30.46.5117.07.63
B566701219242833934−5.01−32.86.246.48.56
B1068801473234447234−5.68−38.37.1312.28.51
B156070984144859425−4.87−36.98.3014.69.62
B1769101783228649015−4.77−33.18.7615.49.03
B18343052374860230−5.09−36.58.3612.09.13
B2151601156159077132−5.06−34.19.9312.08.71
B23784034639853828−4.78−35.58.839.19.52
B268300935217178018−5.23−40.26.716.79.60
B276260133714957939−4.68−32.78.6511.09.13
B29533093279568141−5.27−36.38.648.88.78
B3122,600296167598105−4.57−31.311.0814.59.03
B3217,000287551123398−5.50−35.05.9413.38.18
B334260453106857962−5.07−31.76.8012.58.22
B344900108199488245−5.00−33.510.5610.28.70
G166801783293350616−5.20−34.64.758.28.58
G311,9002034305054616−5.04−35.85.797.09.08
G580401855262786627−4.85−33.67.359.98.98
G648901507198877932−5.18−35.08.549.68.67
G780551498237087939−4.88−34.18.389.99.03
G85660955159057237−5.73−37.111.489.08.22
G956301070146359039−5.78−37.410.829.18.20
G10397059810226038−5.92−37.67.392.78.05
G1111,2001679346575015−5.08−33.96.619.48.64
G13481044990956229−5.02−32.411.1111.98.45
S19,700319758533988−5.49−35.08.438.78.20
R168027629823562−5.69−32.95.799.97.53
GN3241928127758915−5.47−41.77.022.97.63
GN8285927741462115−5.00−36.56.893.67.30
GN9462457592794441−4.34−33.47.315.67.69
GN20400052764675546−4.87−31.14.411.36.39
GN2350116151063407123−4.15−28.47.577.56.84
GN274062527775485485−5.04−32.35.293.76.41
GN3225612043335619−5.42−40.14.72−4.37.40
GN3459587591315103110−5.50−36.68.401.76.65
GN375117620839126741−4.65−35.26.903.27.57
GN39291626741266332−5.45−38.44.353.87.05
GN4010,57514972976990112−4.22−31.46.289.97.45
GN444008472548111120−5.07−39.66.793.07.82
GN45279625536272516−4.75−35.47.133.57.45
GN46343335250284714−5.34−38.86.952.97.27
GN48335734650984017−4.60−36.87.943.48.00
GN494167484653110111−5.18−35.98.604.06.94
GN50272330039450021−5.73−34.75.762.66.05
GN53340037655852230−5.63−34.44.882.26.11
GN57676012081101161542−4.91−34.07.174.56.92
GN59275025142060127−5.45−38.17.354.76.99
GR22002504597006−6.20−40.54.95−4.46.53
K156708221153139766−5.61−36.67.210.06.52
K2505084312266635−5.61−40.88.036.17.25
K3468079297463930−5.74−36.18.767.26.28
K4699011891867116836−4.96−37.27.6310.07.50
K574201658128914620−5.24−36.813.8616.07.00
K6133014924310727−5.13−34.17.773.56.63
K7283058145824812−5.34−35.65.025.66.65
K862008861517131696−4.85−36.96.31−0.47.59
K9369066473942817−5.15−36.28.646.87.02
K1050808811064143518−5.35−35.26.332.06.61
K11850558613418−5.57−37.45.79−2.26.71
K121020172645524−5.52−40.26.788.37.57
K134120547758106394−4.50−34.78.21−1.47.69
K144520634112151265−5.28−37.56.548.77.08
KR38283830485147621−6.47−47.65.30−4.67.35
MM 6.4318.3
C 3.996.8
VSD 6.5617.6
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Elgettafi, M.; Elmeknassi, M.; Elmandour, A.; Himi, M.; Lorenzo, J.M.; Casas, A. δ34S, δ18O, and δ2H-δ18O as an Approach for Settling the Question of Groundwater Salinization in Neogene Basins: The North of Morocco in Focus. Water 2022, 14, 3404. https://doi.org/10.3390/w14213404

AMA Style

Elgettafi M, Elmeknassi M, Elmandour A, Himi M, Lorenzo JM, Casas A. δ34S, δ18O, and δ2H-δ18O as an Approach for Settling the Question of Groundwater Salinization in Neogene Basins: The North of Morocco in Focus. Water. 2022; 14(21):3404. https://doi.org/10.3390/w14213404

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Elgettafi, Mohammed, Malak Elmeknassi, Abdenabi Elmandour, Mahjoub Himi, Juan M. Lorenzo, and Albert Casas. 2022. "δ34S, δ18O, and δ2H-δ18O as an Approach for Settling the Question of Groundwater Salinization in Neogene Basins: The North of Morocco in Focus" Water 14, no. 21: 3404. https://doi.org/10.3390/w14213404

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