title: Geochemical impacts of groundwater heat pump systems in an urban alluvial aquifer with evaporitic bedrock.
abstract: In the last decade, there has been an extensive use of shallow geothermal exploitations in urban environments. Although the thermal interference between exploitations has been recently studied, there is a lack of knowledge regarding the geochemical impacts of those systems on the aquifers where they are installed. Groundwater flow line scale and well-doublet scale research work has been conducted at city scale to quantify the geochemical interaction of shallow geothermal exploitations with the environment. A comprehensive analysis was conducted on data obtained from a monitoring network specifically designed to control and develop aquifer policies related to thermal management of the aquifer. The geochemical impacts were evaluated from a thermodynamic point of view by means of saturation index (SI) calculations with respect to the different mineral species considered in the system. The results obtained indicate limited geochemical interaction with the urban environment in most of the situations. However, there are some cases where the interaction of the groundwater heat pump installations with the evaporitic bedrock resulted in the total disablement of the exploitation system operation wells. The application of the tool proposed proved to be pragmatic in the evaluation of geochemical impacts. Injection of water into the aquifer can trigger an important bedrock gypsum and halite dissolution process that is partly responsible for scaling in well casing pipes and collapse of the terrain in the vicinity of injection wells.
authors.affiliation: Geological Survey of Spain (IGME), C/ Manuel Lasala no. 44, 9B, 50006 Zaragoza, Spain.
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Garrido Schneider
authors.affiliation: Department of Earth Sciences, University of Zaragoza, C/ Pedro Cerbuna 12, 50009 Zaragoza, Spain; GHS, Institute of Environmental Assessment & Water Research (IDAEA), CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain. Electronic address: agargil@unizar.es.
authors.forename: Alejandro
authors.initials: A
authors.lastname: García-Gil
authors.affiliation: GHS, Institute of Environmental Assessment & Water Research (IDAEA), CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain.
authors.forename: Enric
authors.initials: E
authors.lastname: Vázquez-Suñè
authors.affiliation: Department of Earth Sciences, University of Zaragoza, C/ Pedro Cerbuna 12, 50009 Zaragoza, Spain.
authors.forename: José Á
authors.initials: JÁ
authors.lastname: Sánchez-Navarro
keywords: Geochemical impacts; Groundwater heat pump; Hydrogeology; Shallow geothermal energy; Urban aquifer