Chemizm wód podziemnych w utworach trzeciorzędowych na obszarze Polski (bez Karpat)

Abstract

CHEMICAL NATURE OF GROUND WATERS IN TERTIARY FORMATIONS WITHIN THE AREA OF POLAND (EXCEPT FOR THE CARPATIANS)

Summary

The article has been written on the basis of the maps worked out by the present authors during the elaboration of the Hydrochemical Atlas of Poland. The article discusses the general mineralization and the chemical composition on of waters in the Pliocene, Miocene (both continental and marine), and Oligocene formations, except for the Carpathian area. A lack of any available, and generally accepted stratigraphical scheme of the Tertiary formations, and the absence of any maps of the extent and thickness of these formations strongly impede the description of the water-bearing horizons in study. Due to a low amount of water, the Pliocene aquifer is rarely under exploitation. Here, waters are characterized by a low mineralization degree, for the most part from 300 to 600 mg/l, only at places to 1000 mg/l. The following chemical composition is typical: HCO^-₃–Ca²⁺–Mg²⁺, occasionally HCO^-₃–SO^2-₄–Ca²⁺– Mg²⁺–Na⁺.

Within the lowland area, waters in the Miocene formations are almost usually fresh. For the most part, their total mineralization amounts to 200–500 mg/l (in 80% of analyses). The article also discusses regions where water mineralization is higher. Here, waters distinguish themselves by a considerably different chemical composition (up to 24 classes). Most often there are found waters of the following types: HCO^-₃–Ca²⁺–Mg²⁺, or HCO^-₃–Ca²⁺. Waters in the marine formations of Miocene age (Carpathian foredeep) reveal considerable differences in both mineralization and chemical composition. Chloride-sodium mineral waters predominate, but within relatively small areas there are found also fresh waters (mainly within the northern part of the foredeep). There are also known sulphate, sulphate-hydrocarbonate, and sulphate-chloride mineral waters distinguished by various cation composition. As far as the Oligocene formations; are concerned, more mineralized waters occur in the western areas of Poland. Here predominate waters characterized by (0,5–1,0 g/l mineralization but there are found also waters that show their mineralization below 0,5 g/l and above 1,0 ,g/l. In the eastern areas of Poland are found mainly waters where mineralization is up to 0,5 g/l only. Towards the Kujawy-Pomerania swell there occur waters, the mineralization of which is also from 0,5 to 1,0 g/l, and only locally it reaches more than 1,0 g/l. The chemical composition of these waters is highly diversified, e.g.: HCO^-₃–Ca²⁺–Mg²⁺, HCO^-₃–Ca²⁺– Na⁺, HCO^-₃–Cl^-– Na⁺, Cl^-– HCO^-₃– Na⁺.

The authors discuss the relation between the hydrochemical anomalies in the Tertiary formations and the geological structure of the basement. A short description is given also of the syngenetic anomalies (colour of waters in the Miocene formations within the lowland area), of the epigenetic anomalies (content of increased amounts of Cl^-), and of the anomalies which do not show here any visible genetical relations (e.g. anomaly in Fe content).