Assessment of the geogenic salinity conditions in the hyporheic zone of the Moszczenica River in the Rogóźno salt dome zone (Zgierz district) based on radium isotopes
On the border of the Kujavian Anticlinorium and the Łódź Synclinorium, the Rogóźno salt dome was formed and broke through the overburden of Mesozoic formations. The groundwater circulating around them leaches the salt body and, being saline, is subject to drainage in the Moszczenica valley. Previous measurements of vertical hydraulic gradients and physicochemical analyses showed conditions favorable for the penetration of aqueous solutions of Zechstein salt into the riverbed, which is particularly intensified at low surface water levels. The main objective of this publication is to determine the origin of groundwater flowing into the hyporheic zone (HZ) of Moszczenica using radium isotopes. Hydrochemical studies were carried out on deep groundwater in the supply area, flow and drainage zones of the Groundwater Body, within the boundaries of which the salt dome is located. The preliminary assessment of the hydrochemical specificity of HZ waters, carried out using the EMMA method, showed that these are waters which, as a mixture, cannot be related to any of the end member elements selected from the set of local groundwaters. Based on previous hydrochemical studies, the share of deep groundwaters in the HZ was determined to be 22–33%. On this basis, the reconstruction of the sought mixing end element was performed with the isotopic signature of the river water and the mixture of HZ waters. Using several computational scenarios, it was indicated that these may be waters from deep parts adjacent to the salt diapir of Cretaceous aquifers from the southwest
