Groundwater Characterization Using Advanced Analytical Methods

The concentrations of oxygen, NO ${}_3^{-}$ , and SO ${}_4^{2-}$ were measured as detailed in Lazar et al. (2017 (link)). Changes in the oxygen concentrations were measured in the headspace of the oxic incubations using a 5890A gas chromatograph (Hewlett-Packard, USA) with a thermal conductivity detector. The different anions in the groundwater were measured on an ion chromatography system DX-500 (Thermo Fisher Scientific GmbH, Dreieich, Germany) or ICS-5000 (Thermo Fisher Scientific GmbH, Dreieich, Germany). The hydrogen isotope compositions of the water were analyzed using a high-temperature reactor (TC/EA) coupled online via a ConFlo III interface to a Delta+ XL isotope ratio mass spectrometer (all units from Finnigan MAT). The results were calibrated using in-house standards and the Vienna Standard Mean Ocean Water (VSMOW) and Standard Light Antarctic Precipitation (SLAP), according to Gehre et al. (2004 (link)).