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| Titel |
Estimation of groundwater age in the central part of the Baltic Artesian Basin based on new isotope data from Latvia |
| VerfasserIn |
Alise Babre, Andis Kalvāns, Konrāds Popovs, Inga Retike, Aija Delina |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250114212
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| Publikation (Nr.) |
 EGU/EGU2015-14521.pdf |
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| Zusammenfassung |
| Hydrogeological conditions of the Baltic Artesian basin (BAB) have changed rapidly during
the Quaternary period. Therefore this work aims to give better overview of the complexity of
the groundwater recharge and discharge dynamics beyond country borders, taking into
account only shared geological framework, common climate conditions and geological
development. To maintain better understanding of the processes that took part in the
formation of groundwater that can be observed nowadays several methods were
applied placing major emphasis on the new oxygen and hydrogen stable isotope ratio
results.
Earlier investigations in the northern part of the basin indicated glacial melt
water intrusion in the Cambrian-Vendian. Several radiocarbon and stable isotope
studies in groundwater have been done at the southern part of the basin as well
reporting extensive groundwater recharge during the Late Pleistocene suggesting that
recharge took place under different recharge mechanisms compared with the northern
part.
In 2010 to 2012 an extensive field campaign was undertaken, collecting more than 300
groundwater samples for deuterium and stable oxygen, 30 for stable carbon and 10 for
radiocarbon analysis mostly from central part (Latvia) of the BAB covering all the major
aquifer systems where previously collected data was sparse or absent. A specific motivation
for the research was to identify relict glacial meltwater in the groundwater system. The
broader aim was to estimate the baseline isotopic composition of groundwater in the region.
Here a new data set is presented.
Na-Ca-Cl brine found at the deepest – stagnation zone and is characterized by δ18O
values above -5 oÂand δD values approaching -40 oÂin respect to VSMOW. The slow
exchange zone is characterized by δ18O values around -11.7 oÂand δD values around -84.8
oÂ. Mean δ18O and δD value of the groundwater in the active water exchange zone is -11.0
oÂand 79.2 oÂrespectively.
Characteristically the groundwater in the active and slow exchange zone is more
depleted comparing to the precipitation values observed in the eighties and the
depletion is increasing with depth down to the level where strongly enriched brines are
encountered.
Absence of radiocarbon in the deepest aquifers show that groundwater recharged before
last glaciation.
The research is supported by the European Union through the ESF Mobilitas
grant No MJD309 and the European Regional Development Fund project
Nr.2013/0054/2DP/2.1.1.1.0/13/APIA/VIAA/007 and NRP project EVIDENnT
project "Groundwater and climate scenarios" subproject "Groundwater Research". |
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