ALBERT

Description: This dataset contains measured labile particulate and total particulate trace element concentrations (Al, Ti, V, P, Fe, Mn, Co, Ni, Cu, and Cd) of water bottle samples collected during GEOTRACES expedition GN05 (PS100) between 21 July and 1 September 2016 on Northeast Greenland Shelf. Samples were collected using the ultra-clean CTD rosette, equipped with 24 × 12 L GoFlo bottles following GEOTRACES sampling protocols (Cutter et al., 2017; https://www.geotraces.org). Particulate TM samples were collected onto pre-acid leached Polyethersulfone (PES) Membrane filters (0.2 µm, Sartorius) with 1.2 - 4.1 L of seawater filtered per sample. Labile particulates were determined after applying a weak acid leach with a mild reducing agent and a short heating step with a total leach time of 2 h. Total particulates were then analyzed following a 15 h reflux digest at 150 °C using a mixture of hydrofluoric acid and nitric acid. The validation of labile and total particulate trace metal analyses was monitored by reference materials BCR-414 and PACS-3. Information on the analytical procedure including reference materials and limits of detection can be found in related published manuscripts. The concentrations reflect the mean and the corresponding uncertainty is calculated as the standard deviation to replicate measurements. Uncertainty is calculated as one standard deviation (1σ, STD) to replicate measurements via ICP-MS. Use of quality flags (QF) according to GEOTRACES policy (https://www.geotraces.org/geotraces-quality-flag-policy/).

Description: This dataset contains measured dissolved trace element concentrations (Fe, Mn, Co, Ni, Cu, Zn, Cd and Pb) of station depth profiles sampled in Fram Strait (North Greenland Sea) during GEOTRACES expedition GN05 (PS100) between 21 July and 1 September 2016. Samples were collected strictly following GEOTRACES guidelines (Cutter et al., 2017; https://www.geotraces.org) and analysed exactly as per Rapp et al., 2017 ( Anal. Chim. Acta; doi:10.1016/j.aca.2017.05.008). Concentrations were intercalibrated with GEOTRACES reference materials SAFe S and GSC (Bruland Research Lab), with exception of dissolved Cd data. Information on the analytical procedure including reference materials and limits of detection can be found in related published manuscripts, the PhD thesis of Stephan Krisch (Christian-Albrechts-Universität zu Kiel) or can be obtained from the authors upon request. Table caption: Measured concentrations of dissolved trace elements in Fram Strait sampled during GEOTRACES expedition GN05 (PS100) between 21 July-1 September 2006. Uncertainty is calculated as one standard deviation (1σ, STD) to replicate measurements via ICP-MS. ND = no data. Use of quality flags (QF) according to GEOTRACES policy (https://www.geotraces.org/geotraces-quality-flag-policy/). Plesae note, dissolved Cd data is not quality controlled. Somes samples were pooled (indicated in column "Bottle") from different bottles at one depth; the concentrations reflects the mean and the corresponding uncertainty is calculated as the standard deviation to replicate measurements. Trace metal concentrations at station 24 may show larger variations between different bottles at one specific depth. Because station 24 is located at Dijmphna Sund entrance sill, we associate these discrepancies to the water column's strong lateral and vertical turbulence (see ucCTD physical oceanography data) (e.g. Mortensen et al. 2011, 2013, Carroll et al. 2017) that goes in hand with localized TM aggregation-dissolution and sediment resuspension processes, thus affecting TM fractionation (e.g. Homoky et al. 2012).

Description: Meteor Cruise M121 was dedicated to the investigation of the distribution of dissolved and particulate trace metals and their isotopic compositions (TEIs) in the full water column of the Angola Basin and the northernmost Cape Basin. A key aim was to determine the driving factors for the observed distributions, which includes the main external inputs, as well as internal cycling and ocean circulation. The research program of the cruise is official part of the international GEOTRACES program (www.geotraces.org) and cruise M121 corresponds to GEOTRACES cruise GA11. Subject of the cruise was the trace metal clean and contamination-free sampling of waters and particulates for subsequent analyses of the TEIs in the home laboratories of the national and international participants. Besides a standard rosette for the less contaminant prone metals, trace metal clean sampling was realized by using for the first time a new dedicated, coated trace metal clean rosette equipped with Teflon-coated GO-FLO bottles operated via a plastic coated cable from a mobile winch of GEOMAR Kiel. The particulate samples were collected under trace metal clean conditions using established in-situ pump systems operated from Meteor’s Aramid line. The cruise track led from Walvis Bay northwards along the West African margin until 3°S, then turned west until the Zero Meridian, which was followed southwards until 30°S. Then the cruise track turned east again until the Namibian margin was reached and then completed the near shore track northwards until Walvis Bay. The track crossed areas of major external inputs including dust from the Namib Desert and exchange with the west African continental margin and with the oxygen depleted shelf sediments of the Benguela upwelling, as well as with the plume of the Congo outflow, that was followed from its mouth northwards. Our investigations of internal cycling included the extremely high productivity associated with the Benguela Upwelling and the elevated productivity of the Congo plume contrasting with the extremely oligotrophic waters of the southeastern Atlantic Gyre. The links between TEI biogeochemistry and the nitrogen cycle forms an important aspect of our study. The major water masses contributing the Atlantic Meridional Overturning Circulation were sampled in order to investigate if particular TEI signatures are suitable as water mass tracers, in particular near the ocean margin and in the restricted deep Angola Basin. A total of 51 full water column stations were sampled for the different dissolved TEIs, which were in most cases accompanied by sampling for particulates and radium isotopes using the in-situ pumps. In addition, surface waters were continuously sampled under trace metal clean conditions using a towed fish and aerosol and rain samples were continuously collected.

Description: The physicochemical characteristics of dissolved organic matter (DOM) strongly influence its interactions with inorganic species such as protons and trace elements in natural waters. We collected water samples at Boknis Eck, a time series station in the Baltic Sea with a low exposure to freshwater inputs, to investigate how seasonal fluctuations impact the proton binding properties of the isolated DOM. We used potentiometric titrations to assess the binding properties of solid-phase extracted DOM (SPE–DOM) over a seasonal cycle. We report and critically analyze the first NICA parameters estimates of carboxylic-like and phenolic-like sites for brackish water SPE–DOM. The total amount of functional groups (QmaxH,tot) showed no seasonal fluctuations and an average value of 136 ± 5.2 mmol·mol C–1. The average proton affinity (logKH) and binding site heterogeneity (m) showed a relatively minor variability for samples obtained between April and September, when the water remained stratified. These results contribute to a better understanding of the ion binding characteristics of DOM in natural brackish waters.

Description: Marine dissolved organic matter (DOM) presents key thermodynamic properties that are not yet fully constrained. Here, we report the distribution of binding sites occupied by protons (i.e., proton affinity spectra) and parametrize the median intrinsic proton binding affinities (log K̅H) and heterogeneities (m), for DOM samples extracted from the North Atlantic. We estimate that 11.4 ± 0.6% of C atoms in the extracted marine DOM have a functional group with a binding site for ionic species. The log K̅H of the most acidic groups was larger (4.01–4.02 ± 0.02) than that observed in DOM from coastal waters (3.82 ± 0.02), while the chemical binding heterogeneity parameter increased with depth to values (m1= 0.666 ± 0.009) ca. 10% higher than those observed in surface open ocean or coastal samples. On the contrary, the log K̅H for the less acidic groups shows a difference between the surface (10.01 ± 0.08) and deep (9.22 ± 0.35) samples. The latter chemical groups were more heterogeneous for marine than for terrestrial DOM, and m2 decreased with depth to values of 0.28 ± 0.03. Binding heterogeneity reflects aromatic carbon compounds’ persistence and accumulation in diverse, low-abundance chemical forms, while easily degradable low-affinity groups accumulate more uniformly in the deep ocean.

Description: The substance Tris (or THAM, 2-amino-2-hydroxymethyl-1,3-propanediol) is used in the preparation of pH buffer solutions for applications in natural water chemistry, including seawater. The development of a chemical speciation model of buffer solutions containing Tris, TrisH+, and the major ions of seawater is desirable, so that the effects of changes in the composition and concentration of the medium on pH can be calculated. The Pitzer activity coefficient equations, commonly used in such speciation models, describe the thermodynamic properties of solutions in terms of interactions between dissolved ions and uncharged solute species. To determine some of these interactions, we have measured solubilities of Tris(s) in water and aqueous solutions of NaCl, TrisHCl, and (TrisH)2SO4 and the solubility of NaCl(s) in aqueous Tris(aq), from 5 to 45 °C. We report measurements of the water activities of Tris solutions at 293.5 K to high supersaturation with respect to the solid. Using the Pitzer equations, we compare our results to literature data yielding stoichiometric dissociation constants of TrisH+ in aqueous NaCl, and to electromotive forces of cells containing dissolved Tris, TrisHCl, and NaCl. Values of parameters for the interactions of Tris with the ions TrisH+, Na+, and SO42– at 25 °C are determined.