Dataset: GT10-11 - GaBa_surface
Deployment: KN204-01

Dissolved Ga and Ba from surface tows from GT10 and GT11 cruises.

Principal Investigator:

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

BCO-DMO Data Manager:

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

Project:

U.S. GEOTRACES North Atlantic Transect (GA03) (U.S. GEOTRACES NAT)

Current State:

Final no updates expected

Version:

30 Aug 2016

Deployment Synonyms:

GA03, GT11, KN204-01A, KN204-01B, USGT-NAT-2011, USGNAZT, GNAT, 316N20111106, KN204-1

Version Date:

2016-08-30

Data URL:

https://www.bco-dmo.org/dataset-deployment/455682/data

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Description

Lab-based measurements of dissolved Gallium (Ga) and Barium (Ba) from surface tows from the 2010 and 2011 US GEOTRACES cruises (GT10 and GT11).

STATUS NOTE: These data were significantly updated on 30 August 2016. A volume correction had not been applied to the previous version, and thus all of the original values needed to be multiplied by 0.9805. This correction has been applied in the 30 August version, now available online. There were also some samples that were re-analyzed for Ba with the values revised accordingly. Additionally, the PIs withdrew the Pb data (in the original version) because higher quality Pb data are already available from these cruises.

Please note that some US GEOTRACES data may not be final, pending intercalibration results and further analysis. If you are interested in following changes to US GEOTRACES NAT data, there is an RSS feed available via the BCO-DMO US GEOTRACES project page (scroll down and expand the "Datasets" section).

Methods & Sampling

Dataset acquisition description

The samples were collected for trace metal determinations at various stations from the RV Knorr using a custom-built US GEOTRACES trace metal clean rosette consisting of an epoxy painted Al rosette frame containing 24x12 L GO-FLO bottles (Cutter and Bruland, 2012). Immediately after the rosette was recovered, the tops of the GO-FLO bottles were covered with plastic bags and the bottles were removed from the frame and carried into the US GEOTRACES clean van for sub-sampling. The GO-FLO bottles were pressurized to 10 psi using 0.2 um-filtered compressed air and samples were filtered through 0.2 um Acropak or membrane filters. All sub-sampling was undertaken in the clean van using rigorous trace metal protocols. Additional surface water samples were collected from a clean underway sampling system (the "GeoFish") and similarly filtered. This dataset contains the surface samples. To see the bottle data, refer to the GT10-11 - GaBa_bottles dataset (see Related Datasets).

Ga and Ba were determined by isotope dilution ICP-MS using a ThermoFisher Element 2 operated in low resolution. For Ga, samples were concentrated using Mg(OH)₂ co-precipitation (Shiller & Bairamadgi, 2006; Zurbrick et al., 2012) while Ba was determined following 20-fold dilution in dilute nitric acid (Shim et al., 2012).

Data Processing Description

Dataset Processing Description

Quality flag: Assignment of quality flag is based on analytical and methodological considerations in conjunction with examination of profiles and replicate analyses. Scheme is based on WOCE bottle flags: good (2), questionable (3), bad (4), not reported (5), and sample not drawn from this bottle (9).

Reporting units are pico- or nano-moles per kg-seawater. Missing data were identified by 'nd'.

Precision: Ga = 6.5% at 30 pmol/kg; Ba = 3% at 37 nmol/kg
Limit of detection: Ga = 2 pmol/kg; Ba = 0.7 nmol/kg

BCO-DMO made the following modifications:
- values of '-999' were replaced with 'nd'.
- blanks (missing data) were replaced with 'nd'.
- parameter names were modified to conform with BCO-DMO and GEOTRACES naming conventions.

Additional GEOTRACES Processing:
After the data were submitted to the International Data Management Office, BODC, the office noticed that important identifying information was missing in many datasets. With the agreement of BODC and the US GEOTRACES lead PIs, BCO-DMO added standard US GEOTRACES information, such as the US GEOTRACES event number, to each submitted dataset lacking this information. To accomplish this, BCO-DMO compiled a 'master' dataset composed of the following parameters: station_GEOTRC, cast_GEOTRC (bottle and pump data only), event_GEOTRC, sample_GEOTRC, sample_bottle_GEOTRC (bottle data only), bottle_GEOTRC (bottle data only), depth_GEOTRC_CTD (bottle data only), depth_GEOTRC_CTD_rounded (bottle data only), BTL_ISO_DateTime_UTC (bottle data only), and GeoFish_id (GeoFish data only). This added information will facilitate subsequent analysis and inter comparison of the datasets.

Bottle parameters in the master file were taken from the GT-C_Bottle_GT10, GT-C_Bottle_GT11, ODF_Bottle_GT10, and ODF_Bottle_GT11 datasets. Non-bottle parameters, including those from GeoFish tows, Aerosol sampling, and McLane Pumps, were taken from the Event_Log_GT10 and Event_Log_GT11 datasets. McLane pump cast numbers missing in event logs were taken from the Particulate Th-234 dataset submitted by Ken Buesseler.

A standardized BCO-DMO method (called "join") was then used to merge the missing parameters to each US GEOTRACES dataset, most often by matching on sample_GEOTRC or on some unique combination of other parameters.

If the master parameters were included in the original data file and the values did not differ from the master file, the original data columns were retained and the names of the parameters were changed from the PI-submitted names to the standardized master names. If there were differences between the PI-supplied parameter values and those in the master file, both columns were retained. If the original data submission included all of the master parameters, no additional columns were added, but parameter names were modified to match the naming conventions of the master file.

See the dataset parameters documentation for a description of which parameters were supplied by the PI and which were added via the join method.

More information about this dataset deployment

Funding

Award Number	Funding Source
OCE-0927951	NSF Division of Ocean Sciences

Instruments

GeoFish Towed near-Surface Sampler

Supplied Name: GeoFish

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).

Inductively Coupled Plasma Mass Spectrometer

Supplied Description:

Ga and Ba were determined by isotope dilution ICP-MS using a ThermoFisher Element 2 operated in low resolution

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.

Parameters

Supplied Name	Supplied description	Supplied Units	Standard Name
cruise_id	Official cruise identifier e.g. KN199-04 = R/V Knorr cruise number 199-04.	text	cruise_id
cruise_name	GEOTRACES cruise identifier.	text	cruise_name
station_GEOTRC	Station identifier.	unitless	station
date	Date (UTC).	YYYYmmdd	date_utc
time	Time in HHMM format; 24-hour clock (UTC).	HHMM	time_utc
lat	Latitude. North = Positive.	decimal degrees	lat
lon	Longitude. West = Negative.	decimal degrees	lon
sample_GEOTRC	Unique identifying number for US GEOTRACES samples; ranges from 5033 to 6078 for KN199-04 and from 6112 to 8148 for KN204-01. PI-supplied values were identical to those in the intermediate US GEOTRACES master file. Originally submitted as 'GEOTRC_SAMPNO', this parameter name has been changed to conform to BCO-DMO's GEOTRACES naming conventions.	unitless	sample
Ga_D_CONC_FISH	Dissolved gallium (Ga) in pmol/kg seawater; determined at the University of Southern Mississippi.	pmol/kg	trace_metal_conc
Ga_D_CONC_FISH_FLAG_W	Quality flag for 'Ga'; based on WOCE bottle flags: 2= good; 3 = questionable; 4 = bad; 5 = not reported; 9 = sample not drawn from this bottle.	unitless	q_flag
Ba_D_CONC_FISH	Dissolved barium (Ba) in nmol/kg seawater; determined at the University of Southern Mississippi.	nmol/kg	trace_metal_conc
Ba_D_CONC_FISH_FLAG_W	Quality flag for 'Ba'; based on WOCE bottle flags: 2= good; 3 = questionable; 4 = bad; 5 = not reported; 9 = sample not drawn from this bottle.	unitless	q_flag
GeoFish_id	'GeoFish' tow identifier, numbered consecutively within a cruise. PI-supplied values were identical to those in the intermediate US GEOTRACES master file. Originally submitted as 'GeoF#', this parameter name has been changed to conform to BCO-DMO's GEOTRACES naming conventions.	unitless	tow
event_GEOTRC	Unique identifying number for US GEOTRACES sampling events; ranges from 2001 to 2225 for KN199-04 events and from 3001 to 3282 for KN204-01 events. Values were added from the intermediate US GEOTRACES master file (see Processing Description).	unitless	event
depth	Sample depth. 0 = surface tow.	meters	depth

Database

Contribute Data

Dataset: GT10-11 - GaBa_surface
Deployment: KN204-01

Dataset acquisition description

Dataset Processing Description

Database

Contribute Data

Dataset: GT10-11 - GaBa_surfaceDeployment: KN204-01

Dataset acquisition description

Dataset Processing Description

Dataset: GT10-11 - GaBa_surface
Deployment: KN204-01