GROUNDWATER EXCHANGE IN THE BALTIC SHIELD MARGINAL AREAS AND ADJACENT ARTESIAN BASINS BASED ON ISOTOPE AND HYDROCHEMISTRY DATA. SCIENTIFIC PROBLEMS AND PRACTICAL APPLICATIONS. KARELIAN ISTHMUS

Abstract

Water chemical and isotopic composition (deuterium content and oxygen-18), as well as the activity of tritium in groundwater of Riphean aquifer and Vendian complex in the Karelian Isthmus were studied. Estimation of recharge rate for groundwater of the Vendian complex by tritium yielded groundwater ages up to 100 years for this area, which is located not far from Central Karelian watershed. For the area where the Vendian complex is overlapped by the Kotlin aquiclude, water age varied from several hundreds to several thousands years as determined by the radium/radon method. Isotopic data (δ2H and δ18O) indicate that the Vendian complex has no recharge there, and the complex is therefore protected from contamination from the surface, and at the same time its resources are mainly supplied by lateral inflow. The Ladoga graben is apparently dominated by slow water exchange regime, given that at a depth of 250 m relict waters of the Baltic Ice Lake were identified by isotope and hydrochemical criteria.

Keywords

• karelian isthmus
• groundwater
• chemical and isotopic composition
• conditions of resource formation
• water exchange time
• protection against pollution