Carbon isotopic composition of fresh groundwater in the territory of Belarus (in the context of its vulnerability estimation)

Investigations of the distribution of the carbon isotopes (14C, 13C) at water intakes used for drinking water supply of Minsk (Quaternary and Upper Proterozoic aquifers complexes) and Gomel (Cretaceous and Paleogene aquifers) became the first stage of works aimed at the estimation of vulnerability of fresh groundwater aquifers in Belarus. The radiocarbon concentrations obtained and corrections for carbon stable isotopes were used to calculate the formal and corrected radiocarbon age (time of occurrence in an aquifer) of fresh groundwater of the studied aquifers. So, the most ancient radiocarbon age is characteristic of water samples from the Upper Proterozoic aquifer of Belarusian hydrogeological massif in the Minsk region (12,000-14,000 years). Fresh groundwater from the Cretaceous aquifer in the junction zone of the Pripyat artesian basin and Voronezh hydrogeological massif (Gomel region) show wider age range (7000-15,000 years). As aquifers of Belarus become younger, the groundwater isotope composition area comes more similar to the recent water area (II). An analysis of isotope ratios suggests (area I) that only a part of groundwater samples from Cenozoic aquifers (Paleogene and Quaternary Dnieper-Sozh horizon is found in the area of radioactive decay (this is more typical for water from Paleogene aquifer) and may corresponds to the actual time of its occurrence in an aquifer.