Methods:Sampling:•Rhizon technique (Seeberg-Elverfeldt et al. 2005)SO42-•Ion chromatography (Metrohm IC Net 2.3)Fe2+•Ferrozine method (Stookey 1970)NH4+•conductometricallyAlkalinity•Titration with HClδ56Fepw•Removal of salt matrix by column chromatography (NTA Superflow columns, Qiagen) (Lohan et al. 2005)•Column separation using the Dowex 1X8 resin•Isotope analysis on a ThermoFinnigan Neptune Multicollector-ICP-MS (ESI Apex-Q desolvator, standard-sample bracketing method with IRMM-014) (Schoenberg and von Blanckenburg 2005)