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| Titel |
Hydrogeochemical processes and geochemical modeling in a coastal aquifer: Case study of the Marathon coastal plain, Greece |
| VerfasserIn |
Panagiotis Papazotos, Ioannis Koumantakis, Andreas Kallioras, Eleni Vasileiou, Maria Perraki |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250137868
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| Publikation (Nr.) |
 EGU/EGU2017-722.pdf |
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| Zusammenfassung |
| Determining the hydrogeochemical processes has always been a challenge for scientists. The
aim of this work is the study of the principal hydrogeochemical processes controlling
groundwater quality in the Marathon coastal plain, Greece, with emphasis on the origin of the
solutes.
Various physicochemical parameters and major ions of twenty-five groundwater samples
were analyzed. The hydrogeochemical data of groundwater were studied in order to
determine the major factors controlling the chemical composition and hydrogeochemical
evolution. In the Marathon coastal plain, three different zones of the alluvial granular aquifer
system have been detected, considering the geochemical processes and recharge, which affect
its hydrochemical characteristics. The alluvial granular aquifer system is divided eastwards
into three zones: a) the natural recharge zone, b) the reverse ion exchange zone and c) the
diffusion sea water zone. Cl−is the dominant anion and Na+and Ca2+ are the dominant
cations, as determined by plotting the analyses on the respective Piper diagram. Near the
coastline high concentrations of Na+ and Cl− were observed indicating a zone of
seawater intrusion. On the other hand, westward there is increasing concentration of
HCO3− with simultaneous decrease of Na+is indication of a recharge zone from
karstic aquifers of the study area. Between the aforementioned zones there is an
intermediate one, where reverse ion exchange takes place due to high concentrations of
dissolved Na+ and Ca2+ adsorption. The saturation indices (SI) were calculated using
the geochemical modeling software PHREEQC. Mineral phases of halite, sylvite,
gypsum and anhydrite were estimated to be undersaturated in the water samples,
suggesting these phases are minor or absent in the host rock. On the other hand,
calcite, aragonite and dolomite are close to equilibrium; these minerals are present
in the host rocks or in the unsaturated zone, possibly increasing the Ca2+, Mg2+
and HCO3− concentrations when carbonates are dissolved. The analyses of the
bivariate scatter plots, the ionic ratios, the Indices of Base Exchange (IBE), the
Gibbs diagram and the dissolution/precipitation reactions show that evaporation and
water-rock interaction mechanisms such as dissolution of carbonates, followed
by reverse ion exchange, have affected the groundwater chemistry in the study
area.
The results revealed that groundwater chemistry and therefore the origin of the solutes in
the coastal alluvial granular aquifer system of the Marathon coastal plain is primarily affected
by a number of factors such as groundwater and mineral equilibrium, seawater intrusion,
reverse ion exchange and nitrate concentration. A possible future research could focus on the
interaction among hydrogeochemistry, mineral phases and chemical thermodynamic
modeling. |
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