Czynniki kształtujące skład chemiczny wypływów wód podziemnych w południowej części dorzecza Parsęty (Pomorze Zachodnie)

Abstract

Factors affecting the chemical composition of groundwater outflows in the southern part of the Parsêta drainage basin (West Pomerania).A b s t r a c t . In the years 2000–2004, a spring-hydrological research was carried out in the southern part of the Parsęta catchment located in the Drawsko Lakeland, Białogard Plain and Łobez Upland. During hydrochemical mapping performed in 2004, 117 natural groundwater outflows were sampled. The main aim of the study was to determine factors controlling the chemical composition of outflows and to show the influence of the water flow system on water chemistry in a drainage area. The predominant ions in the groundwater outflows were calcium cations and bicarbonate anions, and in the shallow groundwater also sulphates. Factor analysis showed that the basic control of groundwater chemistry was process of chemical weathering (i.e. weathering of aluminosilicates and carbonates, ion exchange) of morainic and fluvioglacial deposits which determined the concentrations of ions such as Ca, Mg, HCO3, and SiO2. Soluble ions are released by decay of organic matter (NO3, SO4, and SiO2) and atmospheric deposition (Cl, SO4 and NO3). Man-made supply locally corresponds to high levels of SO4, Cl, and NO3 ions. The outflows are fed by the near-surface aquifer (local flow system) and intermorainic aquifer (intermediate flow system). The small differences in the water quality of those aquifers resulted from the similarity of their hydrogeochemical environments and were also indicative of their hydraulic connection.