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| Titel |
Geochemical and isotopic investigations on the thermal and mineral underground waters from the Republic of Moldova |
| VerfasserIn |
Barbara Nisi, Oleg Bogdevich, Orlando Vaselli, Igor Nicoara, Franco Tassi, Elena Culighin, Cristina Mogorici, Victor Jeleapov, Mario Mussi |
| 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 |
250143257
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| Publikation (Nr.) |
 EGU/EGU2017-6962.pdf |
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| Zusammenfassung |
| Republic of Moldova (RM) has a large spectrum of underground mineral waters (16
reservoirs) of eight principal aquifers, most of which affected by contaminants originated by
natural sources and anthropogenic activities. Inorganic natural tracers and stable isotopes are
useful tools to fingerprint the water source and solutes, respectively. The aim of this
investigation was to determine the geochemical and isotopic features of the most
important thermo- and mineral waters from RM to trace their flow pathways and
evaluate the presence of deep fluid sources discharging from fault systems, developed
in response to the structural setting of the area. To the best of our knowledge, no
systematic geochemical investigations were previously carried out in this area. RM has
an area of 33,840 km2 and lies within the East European Precambrian Platform,
two structural and/or stratigraphic layers, which are distinguishable in basement
and sedimentary cover in the northern and central part of country. The basement
rocks include granites, gneisses and gabbros. The sedimentary cover, overlying the
crystalline basement, is almost undeformed and consists of Upper Proterozoic,
Mesozoic and Cenozoic rocks. The geological structure is like a matrix formed from
different layers of rocks consisting of permeable and impermeable strata. The deep
aquifers are situated down to 1,000 m depth from the bottom to the top: Vendian
(Ediocariam) and crystalline basement rocks, Silurian crystalline limestone, Cretaceous
limestone, Baden-Sarmatian limestone and clay-sand deposits, middle Sarmatian
limestone and clay-sand layers. Other younger aquifers were not investigated. In
this framework, 54 samples from the most important underground reservoirs of
RM were collected and analyzed for major, trace species and dissolved gases. An
inventory of isotopic (18O/16O and 2H/1H ratios in water and 13C/12C in dissolved
CO2) features (including tritium units in selected samples) was also provided. By a
geochemical point of view, the Moldavian waters showed neutral to alkaline pH, Total
Dissolved Solids between 515 and 75,846 mg/L and mostly negative Eh values. They
displayed a relatively high variability in terms of composition, being classified as
Ca(Mg)-HCO3(SO4), Na-Cl and Na-HCO3. In the mineralized waters from the
Baden-Sarmatian aquifer, trace element distribution revealed significant anomalies for F−, I−
and Br- (up to 13.2, 23.7 and 140.5 mg L−1, respectively). Moreover, high values of
As and Ni were found in the Dubasari waters (up to 13.8 μg L−1 and 43 μg L−1,
respectively). Dissolved gases were mainly dominated by N2 (from 0.16 to 0.78 mmol/L),
while CO2 and CH4 were between 0.02 and 0.66 mmol/L and 0.00005 and 0.44
mmol/L, respectively. Oxygen and hydrogen isotopic ratios were ranging from
-15.8 to -0.9 ‰ (V-SMOW) and from -104.5 to -32.8 ‰ (V-SMOW), respectively,
suggesting a meteoric source slightly modified by prolonged water-rock interactions.
Carbon isotopes in dissolved CO2 were very variable (13δ-CO2from -25.2 to +2.8 ),
the most positive values being associated with the waters collected from the oil
field in the southernmost part of the country. Finally, water ages by using tritium
units (presently in progress) will be used to trace the flow of the youngest waters. |
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