The geochemical study of groundwaters from Cenozoic aquifers in the Gwda catchment (Western Pomerania, Poland)

摘要

The article presents the hydrogeochemical characteristics of deep Cenozoic aquifers occurring in the Gwda catchment (4943 km(2)). The study catchment contains significant resources of good quality fresh groundwater primarily in the Miocene and Lower Pleistocene aquifers. Their range significantly exceeds the area of this catchment. One of the tasks indirectly associated with the Water Framework Directive 2000/60/EC is the description of the variability of the chemical composition of these aquifers. The variability of the main ion concentrations was studied along a profile circa 65 km in length. The chemical composition of groundwater in the study area is primarily determined during the percolation of groundwater into shallow aquifers (Top and Middle Pleistocene) and does not undergo significant modification during the percolation of the groundwater into deeper aquifers (Miocene and Lower Pleistocene). The chemical composition of groundwater from the Miocene and Lower Pleistocene aquifers is locally significantly modified by geogenic processes, such as the oxidation of pyrites, the mixing of brine with fresh groundwater in the ascension sites, or ion exchange. The probably significant hydraulic connection between shallow and deep aquifers indicates the potential seepage of pollutants from shallow Pleistocene to deep Miocene aquifers.