The data set contains the results for the porewater composition of samples, collected from different (up to 11) depths (down to 4.5 mbsf) at two sites in front of the Hütelmoor, southern Baltic Sea. Porewater was under impact by submarine groundwater discharge and collected during 6 field campaigns in years 2020 and 2021 using permanent multi-port samplers. Stable isotope signatures (H, C, O, S), major, and trace element data are presented to characterize the mixture between the endmembers freshwater and the brackish surface water component, superimposed by benthic diagenesis.

This study aimed to characterize the composition of submarine groundwater discharge at the shoreline of the Puck Bay, southern Baltic Sea. Porewater was sampled at various depths down to 50 cm using push point lances with PE syringes and filtered (0.45 µM, disposable cellulose acetate filters) for analysis of for major and trace metals and selected nutrients by ICP-OES (iCAP, 7400, Duo Thermo Fischer Scientific), dissolved ammonium (NH4+) by QuAAtro Analyzer System, total sulphide with a Specord 40 spectrophotometer (Analytik Jena), dissolved inorganic carbon (DIC) and δ13CDIC with an isotope gas mass spectrometer (MAT 253) coupled to a Gasbench II, and δ18OH2O, and δ2HH2O with a CRDS system (laser cavity-ring-down-spectroscopy, Picarro L2140- I). For radium (Ra) isotopes, 5-10 liters of porewater were transferred into canisters without filtration using a peristaltic pump and filtered through a Mn fiber to extract the Ra. The Ra isotopes (224Ra, 223Ra) were measured within 3 and 10 days using radium delayed coincidence counters (RaDeCC). In addition, seepage meters were used to measure seepage water fluxes and to collect samples for the above-mentioned analyses. Sediment cores were taken, sliced at 2 to 4 cm resolution and analyzed for contents of total carbon, nitrogen, and sulphur using an Elemental Analyzer (Euro Vector EuroEA 3, 052), inorganic carbon using an Elemental Analyzer multi EA (Analytik Jena), and total mercury using a DMA-80 analyzer.

This study aimed to characterize the composition of submarine groundwater discharge at the shoreline of the Puck Bay, southern Baltic Sea. Porewater was sampled at various depths down to 50 cm using push point lances with PE syringes and filtered (0.45 µM, disposable cellulose acetate filters) for analysis of for major and trace metals and selected nutrients by ICP-OES (iCAP, 7400, Duo Thermo Fischer Scientific), dissolved ammonium (NH4+) by QuAAtro Analyzer System, total sulphide with a Specord 40 spectrophotometer (Analytik Jena), dissolved inorganic carbon (DIC) and δ13CDIC with an isotope gas mass spectrometer (MAT 253) coupled to a Gasbench II, and δ18OH2O, and δ2HH2O with a CRDS system (laser cavity-ring-down-spectroscopy, Picarro L2140- I). For radium (Ra) isotopes, 5-10 liters of porewater were transferred into canisters without filtration using a peristaltic pump and filtered through a Mn fiber to extract the Ra. The Ra isotopes (224Ra, 223Ra) were measured within 3 and 10 days using radium delayed coincidence counters (RaDeCC). In addition, seepage meters were used to measure seepage water fluxes and to collect samples for the above-mentioned analyses. Sediment cores were taken, sliced at 2 to 4 cm resolution and analyzed for contents of total carbon, nitrogen, and sulphur using an Elemental Analyzer (Euro Vector EuroEA 3, 052), inorganic carbon using an Elemental Analyzer multi EA (Analytik Jena), and total mercury using a DMA-80 analyzer.

This investigation was conducted to evaluate diagenetic elemental fluxes and different freshwater sources, including submarine groundwater discharge, in the water column of Puck Bay (Poland), southern Baltic Sea. Surface water samples were taken in June 2021. Water was pumped through a filter cartridge (1 µM pore size) into barrels and then through manganese-coated acrylic fibers to extract radium (Ra) isotopes. The Ra isotopes (224Ra, 223Ra) were measured within 3 and 10 days using radium delayed coincidence counters (RaDeCC). Subsamples were taken via PE syringes and filtered (0.45 µM, cellulose disposable acetate filters) for analysis of dissolved concentrations of major and trace elements and selected nutrients using ICP-OES (iCAP, 7400, Duo Thermo Fischer Scientific), dissolved ammonium (NH4+) by QuAAtro Analyzer System, dissolved inorganic carbon (DIC) and δ13CDIC using isotope gas mass spectrometry (MAT 253 coupled to a Gas bench II), and δ18OH2O, δ2HH2O using a CRDS system (laser cavity-ring-down-spectroscopy, PICARRO L2140- I).