Preliminary Evaluation of the Geothermal Influence on the Hydrogeochemistry of Rhodopes’ Coastal Aquifer (NE Greece)

The coastal region of Rhodope (NE Greece) is characterized by increased salinization risk leading to groundwater quality degradation and water scarcity. In the context of the MEDSAL Project ( www.medsal.net ), a comprehensive assessment has been carried out concerning the hydrogeochemical characteristics of the area while evaluating the potential impact of geothermal fluids circulation and their ability to move upward and contaminate more surficial water bodies. According to previously conducted surveys, three geothermal wells have been identified in the study area, two of which are representative of the geothermal reservoir, which is hosted within Tertiary molassic sediments. To get an insight into the current hydrogeochemical conditions, a sampling campaign was performed, during which 46 groundwater samples were collected and analyzed for a wide set of parameters. Based on the analytical results, elevated concentrations of certain trace elements presumably associated with geothermal activity (indicatively referred to as B, Li, Sr, and U) have been detected in groundwater wells close to the geothermal one, indicating a possible connection. The relatively elevated groundwater temperature, which reaches up to 25.1 °C, as well as the electrical conductivity values, additionally supports the aforementioned connection. In order to better understand the potential connection of the geothermal influence, the analytical results have been further processed using different tools. The outcomes of the spatial distribution of Li, U, and Ce denoted that the groundwater wells, which are located close to the reported tapped geothermal reservoir and the dominant tectonic structures that prevail in the area, seem to follow a similar hydrogeochemical pattern.