Variability of chemical composition of groundwater at the Miocene aquifer in the Poznań-Gostyń fault graben region (Poland)

Authors:

• Marcin Siepak,
• Karel Novotný,
• Tomáš Vaculovič,
• Józef Górski,
• Jan Przybyłek

Abstract

The paper presents the results of determinations of physicochemical parameters including a wide range of micro components of the groundwater at the Miocene aquifer in Wielkopolska (Poland). The sampling comprised 133 wells within the region of the Poznań-Gostyń fault graben and the Szamotuly structure. A detailed analysis of the study results against the background of the groundwater circulation conditions and geological structure enabled the separation of the zones of water ascent from the Mesozoic basement and the zones of recharge from Quaternary aquifers and the zones where water flows to the discharge zones (transit zones). Within the ascent zone, a zone of water marked by anomalously high colour intensity (>80 mg/1) was separated, connected with the regions marked by the hindered water exchange discussed in the paleohydrogeological aspect. It was stated that the features which distinguish the water ascent zones from the Mesozoic aquifer are: increased concentrations of chlorides (>20 mg/1), low hardness (<4 mval/1) and manganese concentrations <0.1 mg/1. In these zones, clearly increased concentrations of some micro components were also stated, and especially the concentrations of: Cr, Ni, Pb, Li, Mo, V, As, Se, Hg, Ce, La, Nd, Pr and Sm. Within the zone of recharge from the Quaternary aquifers and the zones where water flows to the discharge zones, low concentrations of chlorides (<20 mg/1), hardness at the concentration level >4 mval/1 and manganese concentration >0.1 mg/1 were stated. The determinations of the studied elements were performed using the following analytical techniques: IC, F-AAS, HG-AAS, ICP-AES, ICP-MS and CV-AFS.