Dataset: 2019 BAIT Dissolved Iron Speciation

Name: Dissolved iron speciation results from 2019 Bermuda Atlantic Iron Time-series (BAIT) cruises EN631, AE1909, AE1921, AE1930 in the Western Subtropical North Atlantic Gyre from March to November 2019 (BAIT Project)
Published: 2022-02-14
Keywords: iron speciation, iron, CLE-AdCSV, organic ligands, voltammetry, BATS, oceans

Cite This Dataset

DOI:10.26008/1912/bco-dmo.869081.1

Spatial Extent: N:32.151 E:-63.5796 S:31.1769 W:-64.8147

Temporal Extent: 2019-03-11 - 2019-11-21

Project:

NSFGEO-NERC: Collaborative Research: Using Time-series Field Observations to Constrain an Ocean Iron Model (BAIT)

Program:

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

Principal Investigator:

Kristen Buck (University of South Florida, USF)

Contact:

Kristen Buck (University of South Florida, USF)

Analyst:

Salvatore Caprara (University of South Florida, USF)

BCO-DMO Data Manager:

Sawyer Newman (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

Version Date:

2022-02-14

Restricted:

Validated:

Yes

Current State:

Final no updates expected

Dissolved iron speciation results from 2019 Bermuda Atlantic Iron Time-series (BAIT) cruises EN631, AE1909, AE1921, AE1930 in the Western Subtropical North Atlantic Gyre from March to November 2019 (BAIT Project)

Abstract:

Dissolved iron-binding organic ligand concentrations and conditional stability constants from GO-FLO water column samples collected in 2019 during four Bermuda Atlantic Iron Time-serires (BAIT) cruises in the Bermuda Atlantic Time-series Study (BATS) region.

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Archival Copy

Version Date	Archive	Persistent Identifier	Date Assigned
2022-02-14	Marine Biological Laboratory/Woods Hole Oceanographic Institution Library (MBLWHOI DLA)	10.26008/1912/bco-dmo.869081.1	2023-02-03

Methods & Sampling

Sampling and analytical methodology:

Sample collection and filtering: Water column samples were collected by the BAIT sampling team from 12 trace metal clean modified 6-L Niskin-X samplers (General Oceanics Inc.) deployed on a clean CTD rosette system (Sedwick et al. 2005). The BAIT sampling team filtered the samples through 0.2 µm Supor Acropak filter cartridges (Pall) inside a clean-air laboratory van.

Filtered seawater samples for iron speciation (organic complexation) were collected in 500 mL acid-cleaned Nalgene narrow-mouth fluorinated high-density polyethylene (FPE) bottles that had been filled with Milli-Q for at least two weeks after acid cleaning and rinsed three times with filtered seawater prior to sample collection (Buck et al. 2012). All filtered seawater samples for dissolved iron speciation were frozen at -20 ºC shipboard and shipped to the University of South Florida for laboratory-based analyses post cruise.

Dissolved iron speciation (organic complexation) analyses:

Dissolved iron speciation (organic complexation) was analyzed using competitive ligand exchange- adsorptive cathodic stripping voltammetry (CLE-AdCSV) with salicylaldoxime as the added competing ligand (Buck et al. 2015), modified from the original Rue and Bruland (1995) method. A borate-ammonium buffer was added to all vials, for a final pH of 8.2 (NBS scale; Buck et al. 2007, 2012). Dissolved iron additions of 0 to 10 nM were used in the titrations, for a total of 15 points in each titration. CLE-AdCSV analyses were performed on Bioanalytical Systems (BASi) Controlled Growth Mercury Electrodes (static mercury drop setting, size 14) with Epsilon e2 (BASi) electrochemical analyzers. Deposition time of 120 s was applied to the analyses. There are no reference samples available for iron speciation measurements of iron in seawater, though this method has been shown to compare well with other labs and techniques in GEOTRACES intercalibration exercises (Buck et al. 2012, 2016).

Data Processing Description

Science Data Processing Notes:

CLE-AdCSV data was interpreted using a freely available interpretation program, ProMCC (Omanovic et al. 2015; https://sites.google.com/site/daromasoft/home/promcc), which employs matrix based optimization of titration data fitting to obtain ligand concentrations and conditional stability constants for each sample. Uncertainties in the fitted parameter are presented as the 95% confidence interval provided by the interpretation program. When replicate titrations were conducted, results are presented as averages of the replicates.

Dissolved iron (DFe) concentrations determined by inductively coupled plasma-mass spectrometry (ICP-MS) by Bettina Sohst in project PI Peter Sedwick’s lab at Old Dominion University were used in the ProMCC interpretation program to calculate ligand concentrations and conditional stability constants from the sample titrations. The DFe values used for this dataset are provided in the speciation submission for reference, please see Sedwick’s dataset for the complete dissolved iron data and metadata.

The detection limit for the electroactive Fe-SA complex has been found to be 0.01 nM (Buck et al. 2007), calculated as three times the standard deviation of measured peak height from a 0.05 nM Fe addition to UV-oxidized and chelexed seawater with a 900 s deposition time. For a 90 s deposition time, the detection limit for Fe-SA is ~0.1 nM (Buck et al. 2018).

Data flag notes:

The standard Ocean Data View qualifying flags were used within the flag columns of the dataset (reference all flags at https://www.bodc.ac.uk/resources/delivery_formats/odv_format/):

1: Good Value: Good quality data value that is not part of any identified malfunction and has been verified as consistent with real phenomena during the quality control process. [Used when data were shown to be reproducible]

2: Probably Good Value: Data value that is probably consistent with real phenomena but this is unconfirmed or data value forming part of a malfunction that is considered too small to affect the overall quality of the data object of which it is a part. [Used when the reported value reflects analysis of a single or unverified replicate]

3: Probably Bad Value: Data value recognized as unusual during quality control that forms part of a feature that is probably inconsistent with real phenomena. [Not used]

4: Bad Value: An obviously erroneous data value. [Not used]

5: Changed Value: Data value adjusted during quality control. [Not used]

6: Value Below Detection Limit: The level of the measured phenomenon was too small to be quantified by the technique employed to measure it. The accompanying value is the detection limit for the technique or zero if that value is unknown. [Not used]

7: Value in Excess: The level of the measured phenomenon was too large to be quantified by the technique employed to measure it. The accompanying value is the measurement limit for the technique. [Not used]

8: Interpolated Value: This value has been derived by interpoloation from other values in the data object. [Not used]

9: Missing Value: The data value is missing. Any accompanying value will be a magic number representing absent data. [Any missing data reflect samples that were not analyzed or were analyzed but results are not (or not yet) reported; “nd” = “no data” used in these cases]

A: Value Phenomenon Uncertain: There is uncertainty in the description of the measured phenomenon associated with the value such as chemical species or biological entity.

BCO-DMO Processing Notes

Spaces within column headers were replaced with underscores
Special characters removed from column name (% changed to Percent)

Data Files

File
dataset_buckcaprara_bait_fespeciation-1.csv (Comma Separated Values (.csv), 18.05 KB) MD5:2e845a19096ade65dff0d100fc995c07 Primary data file for dataset ID 869081

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-1829777

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
AE1909	GApr13 BAIT-II Bermuda Atlantic Iron Time-series (BAIT) program Bermuda Atlantic Time-series Study (BATS) BATS359 BAIT02	2019-05-11	R/V Atlantic Explorer	Rodney J. Johnson (Chief Scientist)	data info
AE1921	GApr13 BAIT-III Bermuda Atlantic Iron Time-series (BAIT) program Bermuda Atlantic Time-series Study (BATS) BATS357 BAIT03	2019-08-16	R/V Atlantic Explorer	Rodney J. Johnson (Chief Scientist)	data info
AE1930	GApr13 BAIT-IV Bermuda Atlantic Iron Time-series (BAIT) program Bermuda Atlantic Time-series Study (BATS) BATS365 BAIT04	2019-11-15	R/V Atlantic Explorer	Rodney J. Johnson (Chief Scientist)	data info
EN631	GApr13 BAIT-I Bermuda Atlantic Iron Time-series (BAIT) program Bermuda Atlantic Time-series Study (BATS) BATS BAIT01	2019-03-10	R/V Endeavor	Rodney J. Johnson (Chief Scientist)	data info

Instruments

BASi Controlled Growth Mercury Electrode

Supplied Name: Bioanalytical Systems (BASi) Controlled Growth Mercury Electrodes

Supplied Description:

CLE-AdCSV analyses were performed on Bioanalytical Systems (BASi) Controlled Growth Mercury Electrodes (static mercury drop setting, size 14) with Epsilon e2 (BASi) electrochemical analyzers. Deposition time of 120 s was applied to the analyses.

Instrument Type

Generic Name: BASi Controlled Growth Mercury Electrode

Acronym: BASI CGME

Generic Description:

Bioanalytical Systems (BASi) Mercury drop electrodes are generated by the BASi Controlled Growth Mercury Electrode (CGME) in three modes:

DME (Dropping Mercury Electrode) - mercury is allowed to flow freely from the reservoir down the capillary and so the growth of the mercury drop and its lifetime is controlled by gravity. (The optional 100 um capillary is recommended for this mode.)

SMDE (Static Mercury Drop Electrode) - the drop size is determined by the length of time for which the fast-response capillary valve is opened, and the drop is dislodged by a drop knocker. The dispense/knock timing is microprocessor-controlled and is typically coordinated with the potential pulse or square-wave waveform. This mode can also used to generate the Hanging Mercury Drop Electrode required for stripping experiments.

CGME (Controlled Growth Mercury Electrode) - the mercury drop is grown by a series of pulses that open the capillary valve. The number of pulses, their duration, and their frequency can be varied by PC control, providing great flexibility in both the drop size and its rate of growth. This CGME mode can be used for both polarographic and stripping experiments.

http://www.basinc.com/products/ec/cgme.php

Niskin bottle

Supplied Name: 6-L Niskin-X samplers (General Oceanics Inc.)

Supplied Description:

Water column samples were collected by the BAIT sampling team from 12 trace metal clean modified 6-L Niskin-X samplers (General Oceanics Inc.) deployed on a clean CTD rosette system (Sedwick et al. 2005). The BAIT sampling team filtered the samples through 0.2 µm Supor Acropak filter cartridges (Pall) inside a clean-air laboratory van.

Instrument Type

Generic Name: Niskin bottle

Community Identifier: http://vocab.nerc.ac.uk/collection/L22/current/TOOL0412/

Generic Description:

A Niskin bottle (a next generation water sampler based on the Nansen bottle) is a cylindrical, non-metallic water collection device with stoppers at both ends. The bottles can be attached individually on a hydrowire or deployed in 12, 24, or 36 bottle Rosette systems mounted on a frame and combined with a CTD. Niskin bottles are used to collect discrete water samples for a range of measurements including pigments, nutrients, plankton, etc.

Parameters

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

Supplied Name	Supplied description	Supplied Units	Standard Name
CRUISE	cruise number	unitless	cruise_id
PROJECT_CRUISE	BAIT project cruise number	unitless	cruise_id
Cast_Number	cast number	unitless	cast
SAMPLE_ID	sample identifier	unitless	sample
DATE	GMT date when rosette cast or towfish sampling was started, in format YYYY-MM-DD. Format: %Y-%m-%d	unitless	date
LATITUDE	position when sampling cast was started in decimal °N (2 m sample = underway sample collected typically on approach to station).	lat	lat
LONGITUDE	position when sampling cast was started in decimal °E (2 m sample = underway sample collected typically on approach to station).	lon	lon
DEPTH	sample collection depth below sea surface. GeoFish sample assigned 2 m depth.	meters (m)	depth
Fe_D_CONC_BOTTLE	dissolved iron (Fe) concentration value used in the speciation data interpretation. Data received from project PI Peter Sedwick’s lab at Old Dominion University, contact Sedwick for additional information.	nM	trace_metal_conc
L1Fe_D_CONC_BOTTLE	concentration of strongest dissolved iron-binding ligand detected. Units: nM (10-9 M). “nd” for “no data” used when no data available for this sample.	nM	trace_metal_conc
L1_FLAG	Standard Ocean Data View qualifying flags were used (1 = Good Value, 2 = Probably Good Value, 3 = Probably Bad Value, 4 = Bad Value, 5 = Changed Value, 6 = Value Below Detection Limit, 7 = Value in Excess, 8 = Interpolated Value, 9 = Missing Value, A = Value Phenomenon Uncertain). See Processing Notes for full flag details.	unitless	flag
L1_95_Percent_CI	95% confidence limit of [L1] determined from data fit by ProMCC.	nM	q_code
L1Fe_D_LogK_BOTTLE	log conditional stability constant of L1 complexes with iron (log K cond FeL1, Fe1).	unitless	trace_metal_conc
log_K1_FLAG	Standard Ocean Data View qualifying flags were used (1 = Good Value, 2 = Probably Good Value, 3 = Probably Bad Value, 4 = Bad Value, 5 = Changed Value, 6 = Value Below Detection Limit, 7 = Value in Excess, 8 = Interpolated Value, 9 = Missing Value, A = Value Phenomenon Uncertain). See Processing Notes for full flag details.	unitless	flag
log_K1_95_Percent_CI	95% confidence limit of log K1 determined from data fit by ProMCC. No units, K1 has units of M-1. “nd” for “no data” used when no data available for this sample.	unitless	q_code
L2Fe_D_CONC_BOTTLE	concentration of second (weaker) dissolved iron-binding ligand. Units: nM (10-9 M).	unitless	trace_metal_conc
L2_FLAG	Standard Ocean Data View qualifying flags were used (1 = Good Value, 2 = Probably Good Value, 3 = Probably Bad Value, 4 = Bad Value, 5 = Changed Value, 6 = Value Below Detection Limit, 7 = Value in Excess, 8 = Interpolated Value, 9 = Missing Value, A = Value Phenomenon Uncertain). See Processing Notes for full flag details.	unitless	flag
L2_95_Percent_CI	95% confidence limit of [L2] determined from data fit by ProMCC. Units: nM (10-9 M). “nd” for “no data” used when no data available for this sample.	unitless	q_code
L2Fe_D_LogK_BOTTLE	log conditional stability constant of L2 complexes with iron (log K cond FeL2, Fe1). No units, K2 has units of M-1. “nd” for “no data” used when no data available for this sample.	unitless	trace_metal_conc
log_K2_FLAG	Standard Ocean Data View qualifying flags were used (1 = Good Value, 2 = Probably Good Value, 3 = Probably Bad Value, 4 = Bad Value, 5 = Changed Value, 6 = Value Below Detection Limit, 7 = Value in Excess, 8 = Interpolated Value, 9 = Missing Value, A = Value Phenomenon Uncertain). See Processing Notes for full flag details.	unitless	flag
log_K2_95_Percent_CI	95% confidence limit of log K2 determined from data fit by ProMCC. No units, K2 has units of M-1. “nd” for “no data” used when no data available for this sample.	unitless	q_code

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Dataset: 2019 BAIT Dissolved Iron Speciation