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Sebben, M.L.; Werner, A.D.; Graf, T. |
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Title |
Seawater intrusion in fractured coastal aquifers: A preliminary numerical investigation using a fractured Henry problem |
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Year |
2015 |
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Advances in Water Resources |
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85 |
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93-108 |
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Despite that fractured coastal aquifers are widespread, the influence of fracture characteristics on seawater intrusion (SWI) has not been explored in previous studies. This research uses numerical modelling in a first step towards understanding the influence of fracture orientation, location and density on the extent of seawater and accompanying patterns of groundwater discharge in an idealised coastal aquifer. Specifically, aquifers containing single fractures or networks of regularly spaced fractures are studied using modified forms of the Henry SWI benchmark problem. The applicability of equivalent porous media (EPM) models for representing simple fracture networks in steady-state simulations of SWI is tested. The results indicate that the influence of fractures on SWI is likely to be mixed, ranging from enhancement to reduction in seawater extent and the width of the mixing zone. For the conceptual models considered here, vertical fractures in contact with the seawater wedge increase the width of the mixing zone, whereas vertical fractures inland of the wedge have minimal impact on the seawater distribution. Horizontal fractures in the lower part of the aquifer force the wedge seaward, whereas horizontal fractures located within the zone of freshwater discharge enhance the wedge. Inclined fractures roughly parallel to the seawater-freshwater interface increase the landward extent of seawater and fractures perpendicular to the interface inhibit the wedge. The results show that EPM models are likely inadequate for inferring salinity distributions in most of the fractured cases, although the EPM approach may be suitable for orthogonal fracture networks if fracture density is high and appropriate dispersivity values can be determined. |
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0309-1708 |
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THL @ christoph.kuells @ Sebben2015 |
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37 |
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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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2017 |
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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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Herut, B.; Starinsky, A.; Katz, A. |
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Strontium in rainwater from Israel: sources, isotopes and chemistry |
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Journal Article |
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1993 |
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Earth and Planetary Science Letters |
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120 |
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1-2 |
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77-84 |
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Eighteen ram samples from Israel have been analyzed for their chemical composmon and S7Sr/S6Sr ratios The Sr-Isotoplc rahos lie In the range 0 7078 and 0 7092, and the Sr concentrations vary from 1 × 10 -4 to 9 x 10 4 meq Sr/l.
Soluble salts in rainwater are inherited from three major natural sources, seaspray, Recent marine minerals and mineral dust eroded from rock outcrops and soft A mixing model is formulated to apply the chemical composmon of rain (CI and Sr 2+) and ~ts isotopic 87Sr/S6Sr ratio, for the identification and est~mahon of the Sr sources.
All the samples fall within the m~xing space predicted by the model for the three end members mentioned above The data indicate that the most important non-seaspray source contributing d~ssolved salts to the rams m Israel comprises a mixture of Senoman to Eocene chalk (and its weathering products) and Recent marine minerals, from local and imported sources.
Most of the samples (67%) contain 50% or more non-seaspray Sr 0 e, Sr dissolved from dust or Recent marine minerals), whereas 56% of the samples display 87Sr/86Sr ratios lower than 0 7090. The rest represent mixtures of seaspray and Recent marine minerals. |
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Elsevier |
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THL @ luqianxue.zhang @ herut1993strontium |
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95 |
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Author |
Bobba, A.G. |
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Mathematical models for saltwater intrusion in coastal aquifers |
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1993 |
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Water Resources Management |
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7 |
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1 |
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3-37 |
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Flow of freshwater and saltwater intrusion in coastal aquifers has drawn the attention of many investigators. Several laboratory, as well as mathematical models have been developed to study the pattern of flow of groundwater in coastal aquifers. Mathematical models have wider range of application and are the concern of this paper. Due to the complex nature of the problem, each of these mathematical models are based on certain simplifying assumptions and approximations. This paper presents a critical review of various methods of solution which have been proposed. The validity of the results abtained and the limitations of these models are also discussed. |
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1573-1650 |
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THL @ christoph.kuells @ Bobba.1993 |
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14 |
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Nadler, A.; Magaritz, M.; Mazor, E. |
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Title |
Chemical reactions of sea water with rocks and freshwater: Experimental and field observations on brackish waters in Israel |
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1980 |
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Geochimica et Cosmochimica Acta |
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44 |
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6 |
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879-886 |
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Four major processes are observed to take place in the coastal aquifer of Israel, detectable even in the short times of water contact with the carbonate-containing host rocks. Three are chemical reactions, Ca2+-Mg2+ exchange, Na+-Ca2+ or Na+-Mg2+ base exchange, SO2−4 reduction and the fourth is dilution by freshwater. These reactions and their effects on the chemical composition of the waters were demonstrated experimentally. The range of chemical changes observed in the laboratory experiments overlap the range of the studied natural waters. This indicates that simulation of geologically long-term rock-water interaction could be achieved in laboratory experiments even at low temperatures. |
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0016-7037 |
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THL @ christoph.kuells @ Nadler1980 |
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33 |
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