Porewater nutrients of the Northeast Greenland (NEG) shelf sediments from POLARSTERN cruise PS109

Sediment porewater chemistry (nutrient, DIC, sulfide and sulfate) on the Northeast Greenland shelf were assessed with R/V Polarstern during PS109 between September and October 2017 using two cores with pre-drilled holes mounted on a multiple corer (MUC) a camera-equipped multiple corer (TV-MUC; core area 0.007 m²). Upon arrival on deck, Rhizon samplers were inserted carefully into the holes with intervals of 1 cm until 10 cm sediment depth, and 2 cm intervals until 20 cm sediment depth to extract the sediment porewater. To get a total of 9 ml/l porewater for each depth interval, the porewater from both cores was pooled for each depth. For the analysis of DIC, 2 ml/l porewater from each depth was transferred to a glass vial which had been pre-treated with HgCl₂ and stored at 4°C. DIC concentrations were measured using a flow injection system equipped with the Spark Optimas auto-sampler (model 820, Ambacht, Netherlands). For the determination of porewater nutrients, 4 ml/l of porewater was sampled with acid-washed Sarstedt Vials and stored at -20°C. In the laboratory, 4 ml/l was subsampled for phosphate, silicate and ammonium, while 1 ml/l was subsampled for nitrate and nitrite, and subsequently analyzed with a Continuous Segmented Flow Analyser (QuAAtro39, SEAL Analytical, Norderstedt, Germany).