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| Author |
El Yaouti, F.; El Mandour, A.; Khattach, D.; Benavente, J.; Kaufmann, O. |
| Title |
Salinization processes in the unconfined aquifer of Bou-Areg (NE Morocco): A geostatistical, geochemical, and tomographic study |
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Journal Article |
| Year |
2009 |
Publication |
Applied Geochemistry |
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| Volume |
24 |
Issue |
1 |
Pages |
16-31 |
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| Abstract |
Hydrogeological and geochemical data, in conjunction with the results of an electrical imaging tomographic survey, were examined to determine the main factors and mechanisms controlling the groundwater chemistry and salinity of the unconfined aquifer of Bou-Areg, on the Mediterranean coast of NE Morocco. In addition, statistical and geochemical interpretation methods were used to identify the distribution of the salinity. Multivariate statistical analysis (cluster and principal component factors) revealed the main sources of contamination. Groups A, B, and C in the cluster analysis and Factors 1–3 (Factor 1: CE, Cl−, K+, SO42-, and Mg2+; Factor 2: Ca2+, HCO3-, and pH; Factor 3: NO3-) represent the ‘signature’ of seawater intrusion in the coastal zone, the influence of marly-gypsum outcrops in the upstream zone, and anthropogenic sources, respectively. The ionic delta, the ionic ratio, the saturation index, and Stuyfzand’s method were applied to evaluate geochemical processes. The results obtained indicate, on the one hand, the phenomenon of salinization in both the coastal and the upstream zones, and on the other, the dilution of groundwater by recharge. Cation exchange is shown to modify the concentration of ions in groundwater. Locally, with respect to salinization processes in the coastal zone, the results of electrical imaging tomography show that salinity increases both with depth and laterally inland from the coastline, due to seawater intrusion. |
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0883-2927 |
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THL @ christoph.kuells @ ElYaouti2009 |
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21 |
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Pacheco, F.A.L.; Szocs, T. |
| Title |
“Dedolomitization reactions” driven by anthropogenic activity on loessy sediments, SW Hungary |
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Journal Article |
| Year |
2006 |
Publication |
Applied Geochemistry |
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| Volume |
21 |
Issue |
4 |
Pages |
614-631 |
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In the Szigetvár area, SW Hungary, shallow groundwaters draining upper Pleistocene loess and Holocene sediments are considerably contaminated by domestic effluents and leachates of farmland fertilizers. The loess contains calcite and dolomite, but gypsum was not recognized in these sediments. The anthropogenic inputs contain significant amounts of Ca and SO4. The Ca from these anthropogenic inputs is promoting calcite growth, with concomitant consumption of carbonate alkalinity, undersaturation of the system with respect to dolomite, and dolomite dissolution; in brief, is driving “dedolomitization reactions”. Geochemical arguments supporting the occurrence of “dedolomitization reactions” in the area are provided by the results of mass balance and thermodynamic analyses. The mass balances predicted the weather sequence dolomite\textgreatercalcite\textgreaterplagioclase\textgreaterK-feldspar, at odds with widely accepted sequences of weatherability where calcite is the first mineral in the weathering sequence. The exchange between calcite and dolomite can be a side effect of “dedolomitization reactions” because they cause precipitation of calcite. The thermodynamic prerequisites for “dedolomitization reactions” are satisfied by most local groundwaters (70%) since they are supersaturated (or in equilibrium) with respect to calcite, undersaturated (or in equilibrium) with respect to dolomite, and undersaturated with respect to gypsum. The Ca vs. SO4 and Mg vs. SO4 trends are also compatible with homologous trends resulting from “dedolomitization reactions”. |
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0883-2927 |
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THL @ christoph.kuells @ Pacheco2006 |
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35 |
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Zhao, Q.; Su, X.; Kang, B.; Zhang, Y.; Wu, X.; Liu, M. |
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A hydrogeochemistry and multi-isotope (Sr, O, H, and C) study of groundwater salinity origin and hydrogeochemcial processes in the shallow confined aquifer of northern Yangtze River downstream coastal plain, China |
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Journal Article |
| Year |
2017 |
Publication |
Applied Geochemistry |
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86 |
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49-58 |
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Coastal confined groundwater, Salinity, Hydrogeochemcial processes, Multiple environmental tracers |
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Economically developed coastal areas have a high water demand, and their groundwater resources can be threatened by salinization. Many methods and tracers have been used to discriminate the source of salinization because a single method does not yield reliable results. In this paper, the shallow confined coastal plain aquifer, north of the downstream Yangtze River in China, is used as a case study to investigate the origin of the salinity and the relevant geochemical processes for this aquifer. Multiple environmental tracers of major ions, minor ions (Br−, I−), and isotopes (18O, 2H, 13C, 87Sr, 3H, 14C) were used so as to provide reliable conclusions. The TDS distribution of the aquifer has an increasing trend, from below 500 mg/L in the inland areas to more than 20,000 mg/L around the southeast coastline. The water chemical type evolves from HCO3-Ca to Cl-Na as the TDS increases. The results suggest that the groundwater salinity is influenced by seawater intrusion. The seawater proportions in the groundwater samples range from 0.07% to 94.41% and show the same spatial distribution pattern as TDS. The 3H and 14C values show that the highest salinity was mainly caused by a seawater transgression around 6000a B.P. The aquifer is also affected by other hydrogeochemical processes: base exchange has enriched Ca2+ and depleted K+ and Na+, sulfate reduction has reduced the concentration of SO42− and enriched HCO3−, and iodine-rich organic matter decomposition has enriched the concentration of I−. The iodine enrichment also suggests paleo-seawater intrusion. In addition, the precipitation of carbonate minerals has decreased the concentration of Ca2+, Mg2+, and HCO3−, albeit to a limited extent. |
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0883-2927 |
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THL @ christoph.kuells @ Zhao201749 |
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182 |
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Khaska, M.; Salle], C. [L.G.L.; Lancelot, J.; team, A.S.T.E.R.; Mohamad, A.; Verdoux, P.; Noret, A.; Simler, R. |
| Title |
Origin of groundwater salinity (current seawater vs. saline deep water) in a coastal karst aquifer based on Sr and Cl isotopes. Case study of the La Clape massif (southern France) |
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Journal Article |
| Year |
2013 |
Publication |
Applied Geochemistry |
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37 |
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212-227 |
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In this study a typical coastal karst aquifer, developed in lower Cretaceous limestones, on the western Mediterranean seashore (La Clape massif, southern France) was investigated. A combination of geochemical and isotopic approaches was used to investigate the origin of salinity in the aquifer. Water samples were collected between 2009 and 2011. Three groundwater groups (A, B and C) were identified based on the hydrogeological setting and on the Cl− concentrations. Average and maximum Cl− concentrations in the recharge waters were calculated (ClRef. and ClRef.Max) to be 0.51 and 2.85mmol/L, respectively). Group A includes spring waters with Cl− concentrations that are within the same order of magnitude as the ClRef concentration. Group B includes groundwater with Cl− concentrations that range between the ClRef and ClRef.Max concentrations. Group C includes brackish groundwater with Cl− concentrations that are significantly greater than the ClRef.Max concentration. Overall, the chemistry of the La Clape groundwater evolves from dominantly Ca–HCO3 to NaCl type. On binary diagrams of the major ions vs. Cl, most of the La Clape waters plot along mixing lines. The mixing end-members include spring waters and a saline component (current seawater or fossil saline water). Based on the Br/Clmolar ratio, the hypothesis of halite dissolution from Triassic evaporites is rejected to explain the origin of salinity in the brackish groundwater. Groundwaters display 87Sr/86Sr ratios intermediate between those of the limestone aquifer matrix and current Mediterranean seawater. On a Sr mixing diagram, most of the La Clape waters plot on a mixing line. The end-members include the La Clape spring waters and saline waters, which are similar to the deep geothermal waters that were identified at the nearby Balaruc site. The 36Cl/Cl ratios of a few groundwater samples from group C are in agreement with the mixing hypothesis of local recharge water with deep saline water at secular equilibrium within a carbonate matrix. Finally, PHREEQC modelling was run based on calcite dissolution in an open system prior to mixing with the Balaruc type saline waters. Modelled data are consistent with the observed data that were obtained from the group C groundwater. Based on several tracers (i.e. concentrations and isotopic compositions of Cl and Sr), calculated ratios of deep saline water in the mixture are coherent and range from 3% to 16% and 0% to 3% for groundwater of groups C and B, respectively. With regard to the La Clape karst aquifer, the extension of a lithospheric fault in the study area may favour the rise of deep saline water. Such rises occur at the nearby geothermal Balaruc site along another lithospheric fault. At the regional scale, several coastal karst aquifers are located along the Gulf of Lion and occur in Mezosoic limestones of similar ages. The 87Sr/86Sr ratios of these aquifers tend toward values of 0.708557, which suggests a general mixing process of shallow karst waters with deep saline fossil waters. The occurrence of these fossil saline waters may be related to the introduction of seawater during and after the Flandrian transgression, when the highly karstified massifs invaded by seawater, formed islands and peninsulas along the Mediterranean coast. |
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THL @ christoph.kuells @ Khaska2013212 |
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84 |
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Darwish, T.; Atallah, T.; Francis, R.; Saab, C.; Jomaa, I.; Shaaban, A.; Sakka, H.; Zdruli, P. |
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Observations on soil and groundwater contamination with nitrate: A case study from Lebanon-East Mediterranean |
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Journal Article |
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2011 |
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Agricultural Water Management |
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99 |
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1 |
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74-84 |
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The impact of agricultural practices on soil–groundwater quality in the sub-humid Bekaa plain of Lebanon-East Mediterranean was monitored in four fields (F) between July 2007 and July 2009. These were occupied by continuous mint (F1), summer potato/wheat/potato (F2), lettuce/lettuce/potato/wheat/summer potato (F3) and table grapes (F4). N input calculated on a two-year basis, was in the following ascending order F4, F2, F3 and F1. Soil samples, analyzed down to 200 cm depth, showed high nitrate and chloride concentrations at the end of the 2007 and 2008 seasons. Soil chloride and nitrate peaks recorded in October 2007 and 2008 disappeared below 200 cm overwinter. The calculated N biannual discharge ranged from 130 (F4), to 516 (F2), to 778 (F1), to 879 kg ha−1 (F3). Groundwater quality was studied in 21 wells distributed along a sequence stretching from the Litani River to the eastern water dividing line. Based on the nitrate concentrations, the well located at the top of the water dividing line was the only one suitable for drinking purposes. Eight wells were mildly contaminated, therefore suitable for irrigation purposes except for sensitive crops. Twelve wells, positioned in the plain, showed a nitrate level exceeding 200 mg L−1. Protecting the soil and groundwater quality is a top priority to maintain the ecological and agricultural functions of water. |
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Elsevier |
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0378-3774 |
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THL @ luqianxue.zhang @ Darwish2011 |
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48 |
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