Hydrogeochemistry of a wetland area of southwestern Sicily (Italy)

Abstract

The “Preola” and “Gorghi tondi” lakes are the most noticeable wetlands in the Mazara del Vallo territory (south-west Sicily). There are four karst origin lakes located in a natural depression formed by gypsum dissolution and subsequent collapse of the “Calcarenite di Marsala”, a few meters above sea level. Erosion of the depression sides and human activity has caused visible colluvial deposits, which have contributed to a natural filling process of the lakes. A hydrogeological map of the area and the reconstruction of a water circulation model supplying the lakes have been drafted from geochemical and hydrogeological data. It is apparent from 18O values that the well waters are mainly fed by local meteoric water circulating within the calcarenitic aquifer. However, the lake waters chemical composition are very likely controlled by evaporation processes and a complex mixing between seawater and groundwater, depending on seasonal variation in the hydrodynamic equilibrium