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Hanshaw, B.B.; Back, W. |
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Title |
Deciphering hydrological systems by means of geochemical processes |
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Journal Article |
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Year |
1985 |
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Hydrological Sciences Journal |
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30 |
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2 |
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257-271 |
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Abstract |
The distribution of permeability and chemical character of groundwater in carbonate aquifers is significantly influenced by the many diagenetic processes
and reactions that occur in the early development of these rocks. Many of these diagenetic processes occur in the transition zone formed as the carbonate sediments emerge from the marine environment and become fresh-water aquifers. Analyses of trace elements and isotopes
indicate that calcite cements and dolomites are formed in this groundwater mixing zone. Reverse reactions such as mineral dissolution and dedolomitization occur in carbonate aquifer systems. The geochemical reactivity of the fresh-water/salt-water mixing zone results from the nonlinearity of geochemical parameters as a function of ionic strength and causes extensive dissolution in coastal carbonate rocks. Interpretation of geochemical reactions and isotopic composition of groundwater provides a method to determine hydrological parameters
such as porosity, hydraulic conductivity, and groundwater flow rates. This geochemical method is largely independent of the more conventional approach of determining these parameters by an evaluation of physical properties of aquifer systems. |
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0262-6667 |
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THL @ christoph.kuells @ Hanshaw1985 |
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25 |
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Cardenal, J.; Benavente, J.; Cruz-Sanjulián, J.J. |
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Title |
Chemical evolution of groundwater in Triassic gypsum-bearing carbonate aquifers (Las Alpujarras, southern Spain) |
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Journal Article |
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Year |
1994 |
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Journal of Hydrology |
Abbreviated Journal |
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161 |
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1 |
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3-30 |
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A hydrochemical study employing modelling techniques, was carried out using samples taken at 65 points (springs and wells) in Triassic carbonate aquifers (Lújar-Gádor Unit, Alpujárride Complex, Betic Cordillera). These aquifers are made up of limestones and dolomites with some gypsum scattered or interbedded. Though the area is semi-arid, recharge is relatively high because of their mountainous nature. The carbonate rocks contain dense microfissuration; the groundwater flow regime is predominantly diffuse. The karstic forms are in general poorly developed. Two main hydrochemical processes have been identified in these aquifers. One is incongruent dissolution of dolomite that determines the chemical composition of the less mineralised water. The other is dedolomitisation (dolomite dissolution together with calcite precipitation caused by dissolution of gypsum), which becomes predominant when the flow encounters interbedded gypsum. This reaction is also frequently associated with low temperature thermalism, and can play a part in more intense local karstification (cavities, sinkholes, high transmisivity in wells) observed in the sectors of these aquifers where gypsum is more abundant. A reaction path model has been used to simulate the geochemical processes through a hypothetical aquifer (with similar lithology to the Alpujárride carbonate aquifers). Successive stages of evolution through the carbonate sequence, represented by different saturation states with respect to calcite, dolomite gypsum and CO2, have been modelled and then compared with the field data. |
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0022-1694 |
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THL @ christoph.kuells @ Cardenal1994 |
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18 |
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Daniele, L.; Vallejos, Á.; Corbella, M.; Molina, L.; Pulido-Bosch, A. |
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Title |
Hydrogeochemistry and geochemical simulations to assess water–rock interactions in complex carbonate aquifers: The case of Aguadulce (SE Spain) |
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2013 |
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Applied Geochemistry |
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29 |
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43-54 |
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The hydrogeological unit of Aguadulce (Campo de Dalías aquifers, SE Spain) has a complex geometry. This fact, together with a continuous rise in water demand due to intensive agriculture and tourism create problems for groundwater quantity and quality. In this paper classic geochemical tools managed by means of GIS software and geochemical simulations are combined to delineate, identify and locate the possible physicochemical processes acting in the Aguadulce groundwater. Two main aquifers can be distinguished: the carbonate or lower aquifer of Triassic age, and the calcodetritic or upper aquifer of Plio-Quaternary age. Groundwaters from the latter are more saline and, assuming all chlorinity originates from seawater intrusion, the seawater contribution to their composition would be up to 7%. Nevertheless the carbonate aquifer appears not to be homogeneous: it is compartmentalised into 4 zones where different processes explain the different groundwaters compositions. Zone 4 samples (E margin of the carbonate aquifer) resemble those of the Plio-Quaternary aquifer, where calcite precipitation, dolomite and gypsum dissolution and some cation exchange (water–rock interaction) together with seawater–freshwater mixing occur. In contrast, water–rock interaction predominates in zones 1 and 3 of the carbonate aquifer. Moreover, zone 2 samples, located between zones 1 and 3, are explained by water–rock interaction in addition to mixing with Plio-Quaternary aquifer waters. The combination of geochemical simulations with GIS and hydrogeochemical analyses has proven to be effective in identifying and locating the different physicochemical processes in the aquifer areas, thus improving understanding of hydrogeochemistry in complex aquifers. |
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0883-2927 |
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THL @ christoph.kuells @ Daniele2013 |
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19 |
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Edmunds, W.M. |
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Bromine geochemistry of british groundwaters |
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1996 |
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Mineralogical Magazine |
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60 |
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399 |
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275-284 |
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\textlessp\textgreater The concentrations of Br in potable groundwaters in the United Kingdom range from 60 to 340 µg 1 \textlesssup\textgreater-1\textless/sup\textgreater . The occurrence of Br is described in terms of the Br/Cl weight ratio which enables small changes in bromide concentrations to be assessed in terms of salinity. Median values of Br/Cl in groundwaters range from 2.60 to 5.15 × 10 \textlesssup\textgreater−3\textless/sup\textgreater compared with a sea water ratio of 3.47× 10 \textlesssup\textgreater−3\textless/sup\textgreater . In recent shallow groundwaters the Br/Cl ratio is rather variable in response to a range of natural and anthropogenic inputs (marine and industrial aerosols, industrial and agricultural chemicals including road salt). Some slight enrichment in Br/Cl also occurs naturally during infiltration as a result of biogeochemical processes. \textless/p\textgreater |
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0026-461x |
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THL @ christoph.kuells @ Edmunds1996 |
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20 |
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Author |
El Yaouti, F.; El Mandour, A.; Khattach, D.; Benavente, J.; Kaufmann, O. |
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Title |
Salinization processes in the unconfined aquifer of Bou-Areg (NE Morocco): A geostatistical, geochemical, and tomographic study |
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2009 |
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Applied Geochemistry |
Abbreviated Journal |
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24 |
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1 |
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16-31 |
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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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