Dataset: GP17-OCE Dissolved Gallium in the South Pacific Ocean

Name: Dissolved gallium (Ga) from 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
Published: 2024-10-02
Keywords: gallium, GEOTRACES, GP17-OCE, South Pacific Ocean, Southern Ocean, oceans

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Cite This Dataset

Spatial Extent: N:-19.99986 E:-75.09712 S:-67.00022 W:-152.00026

South Pacific and Southern Oceans

Temporal Extent: 2022-12-03 - 2023-01-24

Project:

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

Program:

U.S. GEOTRACES (U.S. GEOTRACES)

Principal Investigator:

Alan M. Shiller (University of Southern Mississippi, USM)

Scientist:

Melissa Gilbert (University of Southern Mississippi, USM)

BCO-DMO Data Manager:

Shannon Rauch (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

Version Date:

2024-10-02

Restricted:

Validated:

Current State:

Data not available

Dissolved gallium (Ga) from 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

Abstract:

Dissolved gallium (Ga) was determined in association with a US GEOTRACES cruise (GP17-OCE/RR2214) in the South Pacific and Southern Ocean. The cruise sampled formation regions for globally distributed water masses, the return flow of Pacific Deep Water into the Southern Ocean, hydrothermally influenced waters, margin waters, and a gradient of low to high productivity with varying limiting nutrients. The cruise track investigates circulation through the Antarctic Circumpolar Current (ACC) and formation of intermediate waters important for upper ocean nutrient supply. The overall circulation/productivity/export/recycling trap of this region also affects how oceanic element-element relationships develop. For Ga, its distribution can provide insight into dust delivery, which recent work has suggested may be higher than previously thought in the study area. Ga's limited reactivity also allows its distribution to be used for water mass deconvolution, which could be usefully applied to the ACC and intermediate water formation regions. Data include dissolved Ga concentrations from bottle and towed fish samples.

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Methods & Sampling

Clean seawater samples were collected using a GEOTRACES CTD referred to as GT-C/12L GoFlo, and also from the Super-GeoFISH towed surface vehicle. For more information, see the GP17-OCE 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; Hatta et al., 2015). Filtered water was collected in 125-milliliter (mL) HDPE bottles (Nalgene) that had been precleaned by soaking in hot 1.2 M HCl (reagent grade) for at least 8 hours with subsequent thorough rinsing with ultrapure distilled deionized water (Barnstead E-pure).

Dissolved gallium (Ga) was determined by isotope dilution ICP-MS using a ThermoFisher Element XR operated in low resolution (Gilbert et al., 2023). Samples (20-30 mL) were concentrated using a SeaFAST system; a dilute HF rinse was used for column cleaning between samples. An enriched isotope spike of known concentration was prepared using purified enriched 71Ga (99.8%), obtained from Oak Ridge National Laboratories. The substantial sample pre-concentration of this method allows for ICP-MS analysis using medium resolution which eliminates isobaric interferences including doubly charged 138Ba with 69Ga.

The reagent blank contribution to the dissolved Ga analysis is typically 0.6 picomoles per kilogram (pmol/kg) and the detection limit (based on 3 times the standard deviation of the blank) is 0.3 pmol/kg. Repeated runs of US GEOTRACES intercalibration samples (GS and GD), in-house reference solutions, and cast overlap samples suggest a precision of ± 4%; the limit of detection for Ga was 1.5 pmol/kg. Recovery of the method, as determined by repeated analysis of a spiked and unspiked seawater sample was 100 ± 7%.

See attached Intercalibration Report for additional information.

Problems/Issues

No problems noted. SeaDataNet quality flags were used.

Data Processing Description

The raw ICP-MS count rate data were converted to concentrations using Excel.

Quality Flags: Quality flags were applied following the GEOTRACES policy (https://www.geotraces.org/geotraces-quality-flag-policy/), which recommends the SeaDataNet Scheme:

0 = no quality control;
1 = good value;
2 = probably good value;
3 = probably bad value;
4 = bad value;
5 = changed value;
6 = value below detection; (see attached Supplemental File for detection limits for Be-7 samples)
7 = value in excess;
8 = interpolated value;
9 = missing value;
A = value phenomenon uncertain.

BCO-DMO Processing

- Imported original file "RR2214_dataTemplate.xlsx" into the BCO-DMO system.
- Renamed fields to comply with BCO-DMO naming conventions.
- Created the Start_ISO_DateTime_UTC field in ISO 8601 format.
- Corrected the latitude and longitude values for event 20230111.0203.001, Sample ID 18120. (Values were reversed in the original file.)
- Removed the following empty fields: Gear_ID, End_Date_UTC, End_Time_UTC, End_Latitude, End_Longitude
- Saved final file as "939225_v1_gp17-oce_dissolved_ga.csv".

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-1925503

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
RR2214	GP17 GP17-OCE 33RR20221201	2022-12-01	R/V Roger Revelle	Benjamin Twining (Chief Scientist) Gregory A. Cutter (Co-Chief Scientist) Jessica N. Fitzsimmons (Co-Chief Scientist)	data info

Instruments

GeoFish Towed near-Surface Sampler

Supplied Name: Super-GeoFISH towed surface vehicle

Supplied Description:

Instrument Type

Generic Name: GeoFish Towed near-Surface Sampler

Acronym: GeoFish

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/31/

Generic Description:

The GeoFish towed sampler is a custom designed near surface (<2m) sampling system for the collection of trace metal clean seawater. It consists of a PVC encapsulated lead weighted torpedo and separate PVC depressor vane supporting the intake utilizing all PFA Teflon tubing connected to a deck mounted, air-driven, PFA Teflon dual-diaphragm pump which provides trace-metal clean seawater at up to 3.7L/min. The GeoFish is towed at up to 13kts off to the side of the vessel outside of the ship's wake to avoid possible contamination from the ship's hull. It was developed by Geoffrey Smith and Ken Bruland (University of California, Santa Cruz).

GO-FLO Bottle

Supplied Description:

Instrument Type

Generic Name: GO-FLO Bottle

Acronym: GO-FLO

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/30/

Generic Description:

GO-FLO bottle cast used to collect water samples for pigment, nutrient, plankton, etc. The GO-FLO sampling bottle is specially designed to avoid sample contamination at the surface, internal spring contamination, loss of sample on deck (internal seals), and exchange of water from different depths.

Inductively Coupled Plasma Mass Spectrometer

Supplied Name: ThermoFisher Element XR

Supplied Description:

High resolution inductively coupled plasma mass spectrometer, Element XR, ThermoFisher

Instrument Type

Generic Name: Inductively Coupled Plasma Mass Spectrometer

Acronym: ICP Mass Spec

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/LAB15/

Generic Description:

An ICP Mass Spec is an instrument that passes nebulized samples into an inductively-coupled gas plasma (8-10000 K) where they are atomized and ionized. Ions of specific mass-to-charge ratios are quantified in a quadrupole mass spectrometer.

SeaFAST Automated Preconcentration System

Supplied Name: SeaFAST system

Supplied Description:

Automated Preconcentration System for Undiluted Seawater, seaFAST, Elemental Scientific.

Instrument Type

Generic Name: SeaFAST Automated Preconcentration System

Generic Description:

The seaFAST is an automated sample introduction system for analysis of seawater and other high matrix samples for analyses by ICPMS (Inductively Coupled Plasma Mass Spectrometry).

Parameters

Date and time formats are described in python strftime() syntax.

Supplied Name	Supplied description	Supplied Units	Standard Name
Station_ID	Station ID number	unitless	station
Event_ID	Event ID number	unitless	event
Start_ISO_DateTime_UTC	Date and time (UTC) when event started in ISO 8601 format Format: %Y-%m-%dT%H:%MZ	unitless	ISO_DateTime_UTC
Start_Date_UTC	Date when event started Format: %Y%m%d	unitless	date
Start_Time_UTC	Time (UTC) when event started Format: %H%M	unitless	time
Start_Latitude	Latitude when event started, S is negative	decimal degrees	lat
Start_Longitude	Longitude when event ended, W is negative	decimal degrees	lon
Rosette_Position	Position of bottle on rosette from which sample was drawn	unitless	bottle
Sample_ID	GEOTRACES Sample ID	unitless	sample
Sample_Depth	Depth of sample in water column	meters (m)	depth
Ga_D_CONC_BOTTLE_hxhmr3	Concentration of dissolved Ga from bottle samples	picomoles per kilogram (pmol/kg)	Ga
SD1_Ga_D_CONC_BOTTLE_hxhmr3	Standard deviation of Ga_D_CONC_BOTTLE_hxhmr3	picomoles per kilogram (pmol/kg)	Ga
Flag_Ga_D_CONC_BOTTLE_hxhmr3	SeaDataNet quality flag for Ga_D_CONC_BOTTLE_hxhmr3	unitless	q_flag
Ga_D_CONC_FISH_dhewdf	Concentration of dissolved Ga from Super-GeoFISH samples	picomoles per kilogram (pmol/kg)	Ga
SD1_Ga_D_CONC_FISH_dhewdf	Standard deviation of Ga_D_CONC_FISH_dhewdf	picomoles per kilogram (pmol/kg)	Ga
Flag_Ga_D_CONC_FISH_dhewdf	SeaDataNet quality flag for Ga_D_CONC_FISH_dhewdf	unitless	q_flag

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Dataset: GP17-OCE Dissolved Gallium in the South Pacific Ocean