Water chemistry of unfiltered groundwater samples from the Fennoscandian Shield deep terrestrial biosphere in 2018 and 2019

Copious amounts of organic carbon are stored for long periods of time in deep continental groundwaters. Little is known about its composition and cycling, mainly due to the difficulties in obtaining sample material. Cool fracture waters of different origins can be obtained under clean conditions at Äspö Hard Rock Laboratory (Äspö HRL, Sweden), operated by the Swedish Nuclear Fuel and Waste Management Company (SKB). We sampled groundwater from different depth (171 to 507 meter below sea level) in the bedrock fractures in November 2018 and March-April 2019. We assessed water chemistry and dissolved organic matter composition via stable carbon isotopic and molecular-formula level analysis in recent Baltic Sea-influenced to old saline fracture waters in the granitic Fennoscandian shield. Physicochemical parameters, major ions, water isotopic compositions (δ18O and δD), total nitrogen as well as dissolved organic matter concentration and stable isotopic composition were obtained for unfiltered groundwater samples from different boreholes.