Variability in chemical composition of waters in the Zoloushka gypsum cave (Ukraine-Moldova) as a consequence of anthropogenic degradation of a karst aquifer

Abstract

The Zoloushka Cave, with passages >90 km long and a volume of ~0.65 million m3, is among the largest gypsum caves in the world. The cave was opened in the course of gypsum excavation in a quarry in the village of Criva (Moldova) located just near the border with Ukraine. During the quarry exploitation, with the accompanying pumping of water, the groundwater table was lowered to the bottom part of the gypsum layer. As a result of the pumping, the karst aquifer within the cave labyrinth was fragmented into separate underground reservoirs controlled by the morphology of the karst system and its content of clay deposits. Currently, there are several dozen lakes in the cave with a varied hydrodynamic regime (relict lakes, lakes with direct and indirect hydraulic connection with the aquifer). Research was carried out in February 2020 to determine the degree of, and reasons for, the hydrogeochemical diversity of 10 selected lakes of various hydrodynamic types present in the cave. The degree of variability of the hydrogeochemical parameters of these lakes was found to depend on a number of factors, mainly: the hydrodynamic type of the cave lake resulting from the degree of its hydraulic connection with the aquifer; the geochemical environment of the lake; and anthropogenic influence. The autonomizing role of these factors is the modification (within individual lakes) of the hydrogeochemical context of the transit waters flowing through the cave system to the quarry.