The groundwater age in the Middle-Upper Devonian aquifer system, Lithuania

Mokrik, R.; Mažeika, J.; Baublytė, A.; Martma, T.

The groundwater age in the Middle-Upper Devonian aquifer system, Lithuania | Das Grundwasseralter des Aquifersystems im mittleren oberen Devon, Litauen L’âge de l’eau souterraine dans le système aquifère Dévonien Moyen-Supérieur, Lithuanie La edad de las aguas subterráneas en el sistema acuífero Devónico medio superior, Lituania A idade da água subterrânea no sistema aquífero Devónico Médio-Superior, Lituânia

2009

Mokrik, R. | Mažeika, J. | Baublytė, A. | Martma, T.

³H, δ¹³C and hydrochemical data were used to estimate the corrected groundwater age derived from conventional ¹⁴C age of dissolved inorganic carbon (DIC). The Middle-Upper Devonian aquifer system from the Baltic upland recharge area in eastern Lithuania towards the discharge area on the Baltic Sea coast in the west was considered. The concentration of total dissolved solids (TDS) in groundwater changes from 300 to 24,000 mg/L and increases downgradient towards the coast. The other major constituents have the same trend as the TDS. The hydrochemical facies of groundwater vary from an alkali-earth carbonates facies at the eastern upland area to an alkali-earth carbonate-sulfate and chloride facies at transit and discharge areas. Meteoric water percolating through the Quaternary and Devonian aquifers regulate the initial ¹⁴C activities of groundwater involving two main members of DIC: soil CO₂ with modern ¹⁴C activity uptake and dissolution of ¹⁴C-free aquifer carbonates. Other sources of DIC are less common. ¹⁴C activity of DIC in the groundwater ranged from 60 to 108 pMC at the shallow depths. With an increase of the aquifers depth the dolomitization of aqueous solution and leakage of the “old” groundwater from lower aquifers take place, traced by lower activities (7–30 pMC).

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