Evaluating a key groundwater ecosystem service: natural nitrate transformation

Groundwater is one of the most important sources of drinking water. The use of groundwater as drinking water is mainly made possible by ecosystem services in aquifers. These include natural water purification, which can lead to a reduction in pollutants. These pollutants are mainly introduced into the groundwater by anthropogenic activities. These pollutants also include nitrate, which endangers the groundwater quality in many aquifers, but which can be converted by the ecosystem service of denitrification and thus removed from the groundwater in a natural way. To date, however, this service has been insufficiently taken into account in the management of aquifers and in guidelines, partly because there is a lack of instruments that can be used to clearly determine the potential for denitrification. In addition, denitrification can be spatially and temporally variable and is dependent on changing hydrogeochemical conditions, which are often unknown. Therefore, the main objective of this project is to identify processes and properties that lead to denitrification in groundwater. To achieve this goal, we investigate nitrate sources and denitrification processes in groundwater using isotope techniques. In addition, we identify hydrogeochemical situations that influence denitrification. For this purpose, we carry out monitoring at selected field sites in Austria, France and Denmark as well as controlled experiments under laboratory conditions. For different land use sites, we will investigate effects such as water level, temperature, redox conditions, organic carbon concentrations and chemical pollution on denitrification in groundwater. Together with national and international project partners in France, Denmark and Austria, we are developing a toolbox to better characterize aquifers with regard to their denitrification potential and to develop new protocols that could eventually be integrated into groundwater quality monitoring guidelines. This FWF-funded project is part of the Water4All project “DeepThought” of the Joint Transnational Call “Aquatic Ecosystem Services”.