Dataset: Dissolved barium (Ba) concentrations in seawater samples collected on the US GEOTRACES GP17-OCE cruise on R/V Roger Revelle (RR2214) in the South Pacific and Southern Oceans from December 2022 to January 2023

Final no updates expectedDOI: 10.26008/1912/bco-dmo.947790.1Version 1 (2025-01-02)Dataset Type:Cruise Results

Principal Investigator, Contact: Tristan J. Horner (Woods Hole Oceanographic Institution)

Co-Principal Investigator: Matthew A. Charette (Woods Hole Oceanographic Institution)

Scientist, Contact: Margot C.F. Debyser (Woods Hole Oceanographic Institution)

Technician: Maureen Auro (Woods Hole Oceanographic Institution)

Technician: Jessica Drysdale (Woods Hole Oceanographic Institution)

Technician: Gretchen Swarr (Woods Hole Oceanographic Institution)

BCO-DMO Data Manager: Shannon Rauch (Woods Hole Oceanographic Institution)


Program: U.S. GEOTRACES (U.S. GEOTRACES)

Project: US GEOTRACES GP17-OCE: Investigating the role of the Southern Ocean's biogeochemical divide in shaping the global distributions of radium and barium isotopes (GP17-OCE Ra and Ba isotopes)

Project: US GEOTRACES GP17 Section: South Pacific and Southern Ocean (GP17-OCE) (GP17-OCE)


Abstract

This dataset includes measurements of dissolved barium (Ba) concentrations in the South Pacific and Southern Ocean from the US GEOTRACES GP17 section (GP17-OCE, Papeete, Tahiti to Punta Arenas, Chile) on R/V Roger Revelle from December 2022 to January 2023.

Clean seawater samples were collected using a GEOTRACES CTD referred to as GT-C/12-liter GoFlo, and also from the Super-GeoFISH towed surface vehicle and from the ship's underway system for 1 sample where bad weather did not allow for the GeoFISH deployment. For more information, see the cruise report. Water samples were filtered through pre-cleaned, 0.2-micrometer (µm) Pall Acropak Supor filter capsules as described elsewhere (e.g., Cutter et al., 2014). Filtered water was collected in 125-milliliter (mL) HDPE bottles (Nalgene) that had been precleaned following the GEOTRACES protocol for trace-metal clean sampling.

Seawater samples were analyzed using a standard methodology for determining dissolved barium (Ba) concentrations in seawater samples. This process involves the use of barium-135 (135Ba) isotope dilution coupled with analysis via inductively coupled plasma mass spectrometry (ICP-MS) using a ThermoScientific iCAP Q operated in Kinetic Energy Dispersion (KED) mode. Solutions containing 100 microliters (μL) of seawater sample, 100 μL of a tellurium (Te) solution, which serves as a monitor for instrumental mass bias, and 100 μL of a 135Ba spike solution were analyzed, eluted to 2 mL with 2% HNO3. The enriched 135Ba isotope spike is BaCO3 obtained from Oak Ridge National Laboratories (batch no.142890) The ratios of barium isotopes, specifically the ratio of 135Ba/137Ba, are measured in the samples. The spike-to-sample ratio is then calculated using standard isotope dilution equations, and the resultant [Ba] in the sample (in nanomoles) was determined based on the quantity of spike added. Optimal spiking is achieved when spiked samples exhibit 135Ba/137Ba between 1.6 and 32.7 (Stracke et al., 2014), noting that our samples exhibited 135Ba/137Ba between 5.65 and 23.40. [Ba] was converted to nanomoles per kilogram (nmol/kg) based on the ocean's average density at the surface, 1.027 grams per cubic centimeter (g/cm3).


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Methods

Cutter, G.A., Andersson, P., Codispoti, L., Croot, P., Francois, R., Lohan, M., Obata, H., van der Loeff, M. R. (2014) Sampling and Sample-Handing Protocols for GEOTRACES Cruises (cookbook) Version 2.0; December 2014.
Methods

Stracke, A., Scherer, E. E., & Reynolds, B. C. (2014). Application of Isotope Dilution in Geochemistry. Treatise on Geochemistry, 71–86. https://doi.org/10.1016/b978-0-08-095975-7.01404-2