Fig. 1: The Äspö HRL tunnel system and sampled boreholes.

Location of the Äspö HRL in Kalmar County, Sweden, is shown in the schematic map; depth, location and water type of samples included in this study are indicated on the tunnel system reproduction. A portion of the tunnel (including boreholes SA1229A_1, KA2051A01_5, and KA3105A_03) extends below the Baltic Sea. Figure reprinted and modified from ref. 94 with permission from Elsevier.