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Pacheco, F.A.L.; Szocs, T. |
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“Dedolomitization reactions” driven by anthropogenic activity on loessy sediments, SW Hungary |
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2006 |
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Applied Geochemistry |
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21 |
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4 |
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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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Post, V.E.A.; Houben, G.J.; van Engelen, J. |
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What is the Ghijben-Herzberg principle and who formulated it? |
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2018 |
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Hydrogeology Journal |
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26 |
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6 |
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1801-1807 |
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It has been suggested in a number of historical notes that it was neither Willem Badon Ghijben nor Alexander Herzberg who formulated the famous principle now carrying their name, which relates the water-table elevation to the depth of the freshwater saltwater interface in coastal aquifers. In this paper, a systematic review of the literature pre-dating the publication of their work is presented. The aim is to establish to what extent these previous works captured the essence of the Ghijben-Herzberg principle, that is, the combination of a correct conceptual model of the hydrogeological conditions with a quantitative relationship. It was found that references to coastal fresh groundwater reserves can be traced back to Roman times, while the earliest detailed descriptions of a freshwater lens that could be found dates from the eighteenth century. The correct understanding of the hydrostatic equilibrium between fresh and salt groundwater is evident in works from the early nineteenth century. However, it was Badon Ghijben and Herzberg who combined this with the correct understanding of the groundwater conditions of a freshwater lens. It was further found that Herzberg had already recorded his findings in 1888 in a hand-written report, confirming speculation that such a report might exist. |
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1435-0157 |
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THL @ christoph.kuells @ Post2018 |
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89 |
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Mahindawansha, A.; Kraft, P.; Külls, C.; Breuer, L. |
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Water flow mechanisms and unproductive water losses in rice-based cropping systems in the humid tropics |
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2021 |
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EGU General Assembly Conference Abstracts |
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21 |
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THL @ christoph.kuells @ mahindawansha2021water |
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209 |
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Garcia*, L.A.; Shigidi, A. |
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Using neural networks for parameter estimation in ground water |
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2006 |
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Hydrogeol. J. |
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318 |
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215-231 |
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CUT @ phaedon.kyriakidis @ Garcia2006 |
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149 |
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Nogueira, G.; Stigter, T.Y.; Zhou, Y.; Mussa, F.; Juizo, D. |
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Understanding groundwater salinization mechanisms to secure freshwater resources in the water-scarce city of Maputo, Mozambique |
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2019 |
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Science of The Total Environment |
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661 |
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723-736 |
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In this study hydrochemical, isotopic and multivariate statistical tools are combined with a recharge analysis and existing geophysical data to improve understanding of major factors controlling freshwater occurrence and the origins of high salinities in the multi-layered coastal aquifer system of the Great Maputo area in Mozambique. Access to freshwater in this semi-arid area is limited by an inefficient public supply network, scarce surface waters, long droughts and an increasing population growth. Groundwater has a large potential to enhance water security, but its exploitation is threatened by both coastal and inland salinization mechanisms that are poorly understood. A GIS approach is utilized to classify potential recharge zones based on hydrogeological properties and land use/cover, whereas potential recharge rates are estimated through a root zone water balance method. In combination with water stable isotope data results reveal that extreme rainfall events provide the most relevant contributions to recharge, and interception and evaporation play an important role in the low recharge areas. Hierarchical clustering of hydrochemical and isotopic data allows the classification of six water groups, varying from fresh to brackish/salt waters. Corresponding scatter plots and PHREEQC modelling show evaporation and mixing with seawater (up to 5%) as major processes affecting salinity in the area. The co-occurrence of high alkalinity and Cl concentrations, in combination with piezometric and geo-electrical data, suggests that: 1) inland brackish/salt groundwater is caused by mixing with seawater trapped within clay layers; and 2) brackish/salt surface waters result from seepage of brackish groundwater into rivers and wetlands, followed by evaporation, hence increasing salinity and δ18O values. Mixing with small fractions of trapped seawater as main salinity source, rather than halite dissolution, is further corroborated by Br/Cl ratios of brackish/salt water samples near the ocean ratio. Cation exchange upon salinization is mainly observed in the semi-confined aquifer, while freshening takes place in the phreatic aquifer, particularly in areas presenting high recharge rates. |
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0048-9697 |
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THL @ christoph.kuells @ Nogueira2019 |
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34 |
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