The use of environmental markers to identify groundwater salinization sources in a Neogene basin, Kert aquifer case, NE Morocco

Abstract

Environmental isotopes data of oxygen and hydrogen of natural water and sulphur and oxygen of dissolved sulphate as well as characteristics of d-excess are used to illustrate the salinity origin in Kert aquifer NE Morocco. In this study, 14 groundwater samples and surface water of the Kert River were collected in the Kert plain during December 2008, and were combined with previously collected hydrochemical data. The isotope compositions of these waters range from -5.74 to -4.51 % for oxygen and from -40.8 to -34.1 % for hydrogen. In Kert River these values are -6.47 % for oxygen and -47.56 % for hydrogen. All the samples with a slope \8 do not fall on the meteoric water line indicating a light evaporation. Water has low and different d-excess values (ranging from ?1.37 to ?9.82 %), reflecting different climatic conditions. Based on the nitrate concentration water in the Kert aquifer comes from the modern precipitation. The isotope compositions range from -2.2 to ?16 % for sulphur and from ?5.02 to ?13.86 % for oxygen. In Kert River these values are -4.6 and ?5.3 % for sulphur and oxygen, respectively. There are fairly constant difference between oxygen of water and the oxygen of sulphate suggesting a dominant control of this latter in sulphate sources. At least three major sulphate sources were identified by the isotope data from sulphate in these waters: (1) dissolved marine sulphate from the underlying upper Miocene unit; (2) dissolved sulphate from Kert River; (3) sulphate derived from oxidation of sulphur compounds in the metamorphic massif of Temsamane. The latter has a dilution role. The isotopic variations of these waters and sulphate concentration therein reflect mixing of these sources in the aquifer.

Determination of Physicochemical Water Quality of the Ghis-Nekor Aquifer (Al Hoceima, Morocco) Using Hydrochemistry, Multiple Isotopic Tracers, and the Geographical Information System (GIS)

“…Our results agree with the results obtained by Elgettafi et al [77]. The analysis of spring water in the Kert aquifer (NE Morocco) shows variations in δ 18 O, ranging from −3.92‰ to −5.60‰ with an average of around −4.56‰ and variations in deuterium from δ 18 O varies between the maximum value of −3.92‰ according to the Vienna Standard Mean Ocean Water (VSMOW) (found in well P1) to the minimum value of −5.60‰ VSMOW (found in well P6) with the mean value around −4.60‰ VSMOW.…”

“…Our results agree with the results obtained by Elgettafi et al [77]. The analysis of spring water in the Kert aquifer (NE Morocco) shows variations in δ 18 O, ranging from −3.92‰ to −5.60‰ with an average of around −4.56‰ and variations in deuterium from −34.10‰ to −40.80‰ with an average of around −32.15‰.…”

“…Moreover, the results obtained from the analysis of spring water from the limestone ridge of the Rif, south and north of Tetouan [77], show variations in δ 18 O ranging from −3.92‰ to −5.60‰ with an average of around −4.6‰ and variations in deuterium from −28.40‰ to −41.70‰ with an average of around −32.15‰ (Table 2). The report of these results in the δ 2 H-δ 18 O diagram shows that all the representative points of the sources are aligned between the two meteoric lines of Craig and of the western Mediterranean, with a regression line of equation δ 2 H = 5.79, δ 18 O = 6.30 (Figure 13) (R 2 = 0.855).…”

“…The report of these results in the δ 2 H-δ 18 O diagram shows that all the representative points of the sources are aligned between the two meteoric lines of Craig and of the western Mediterranean, with a regression line of equation δ 2 H = 5.79, δ 18 O = 6.30 (Figure 13) (R 2 = 0.855). A slope value of 5.8 (less than 8) indicates a tendency for evaporation [77].…”

The Issue of Groundwater Salinization in Coastal Areas of the Mediterranean Region: A Review

“…Early studies in the Mediterranean area were developed in Israel [92,93], while since the year 2005, there has been a growing legacy of studies employing these techniques. Most of the studies used stable isotopes to distinguish between different GW origins [94][95][96][97][98][99][100][101][102][103][104][105][106][107][108][109][110][111][112][113], while some of them used radioactive isotopes to determine the residence time of GW [114][115][116], that is, one of the very few pieces of information allowing researchers to distinguish between actual and paleo SWI. These last elements have also been used to study surface water/groundwater interaction; for example, in a recent paper from Mayer et al [117], short-lived radioactive isotopes, such as radon-222, allowed not only for the determination of the amount of exchange between different water bodies, but also for the ability to precisely derive GW flow velocities and saturated hydraulic conductivities, which are vital parameters to constrain numerical simulations.…”