Hydrogeochemistry and vulnerability of groundwater in the moraine upland aquifers of the Gdańsk region (Northern Poland)

Abstract

The focus of this study was on determination and comparison of natural and current hydrogeochemical features of the groundwater, in order to evaluate changes of water quality and to identify the origin of these changes. Both natural processes and anthropogenic stress affect the chemical composition of groundwater were recognised. In both aquifer groups groundwater chemical composition demonstrates some similarities and is formed by the same kinds of natural processes, which are taking place already in the upper zones of the shallow aquifers, where groundwater is saturated with respect to most of carbonate and clay minerals, as well as minerals containing Fe2+ ions. During seepage into deeper aquifers, water is being enriched with Fe2+ and Mn2+ ions and in some places with SO4 2- and Mg2+ as well. The types and intensity of human activities, as well as the vulnerability of aquifers to contamination, were concluded to play an important role in generating the observed changes in the chemical characteristics of the groundwater. They effect on changes of hydrogeochemical background values (e.g. TDS, N-compounds), the current increase of maximum concentrations of N-compounds, chlorides, sulphates, magnesium and TDS (total dissolved solids).