Natural Fe-binding organic ligands in Fram Strait and over the northeast Greenland shelf

Ardiningsih, Indah; Krisch, Stephan; Lodeiro, Pablo; Reichart, Gert‐Jan; Achterberg, Eric P.; Gledhill, Martha; Middag, Rob; Gerringa, Loes J. A.

doi:10.1016/j.marchem.2020.103815

Cited by 19 publications

(66 citation statements)

References 89 publications

(179 reference statements)

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“…Subsamples for a second DFe determination from the ligand bottles, was analyzed using HR-ICP-MS (Thermo Fisher Element XR) after pre-concentration using an automated SeaFAST system (SC-4 DX SeaFAST pico; ESI), and the quantification was done via standard additions. The procedure is described in detail in Ardiningsih et al (2020). DFe obtained from ligand samples was approximately 15% lower than DFe obtained from immediately acidified samples, as also found by others (Gerringa et al, 2016;Gerringa et al, 2019).…”

Section: Dfe and Fe-binding Ligand Analysissupporting

confidence: 61%

“…This region provides an ideal hydrographic setting for comparing different CLE-AdCSV methods with different ALs. As Ardiningsih et al (2020) showed, there is a difference in ligand properties ([L t ] and log K Fe L ) between three biogeochemical provinces in this area; (1) Fram Strait, (2) Norske Trough and (3) Nioghalvfjerdsfjorden (79N) Glacier terminus, and Westwind Trough. The suspected inflow of relatively weak ligands from the Arctic Ocean with the Polar Surface Water (PSW) in the western Fram Strait results in higher ligand concentrations with lower binding strength in comparison to the eastern side of Fram Strait.…”

Section: Introductionmentioning

confidence: 91%

“…Sampling and sample-handling were done following GEOTRACES sampling procedures for trace elements (Cutter et al, 2010). The detailed sample collection for DFe was reported by Kanzow (2017); (Krisch et al, 2020), and for dissolved Fe-binding organic ligands by Ardiningsih et al (2020). Right after recovery of the trace metal clean rosette and the GO-FLO bottles were carried into a trace metal clean container for filtration.…”

Section: Sample Collectionmentioning

confidence: 99%

“…In un-acidified samples, however, bottle wall adsorption can cause Fe loss (Fischer et al, 2007;Jensen et al, 2020). The analysis of DFe was undertaken using two different subsamples, one immediately acidified onboard (Kirsch et al, unpublished) and a subsample taken from the ligand samples Ardiningsih et al (2020) and available at doi: 10.25850/nioz/7b.b.u). DFe was determined in acidified samples, by isotope dilution high-resolution inductively Bourke et al (1987).…”

Section: Dfe and Fe-binding Ligand Analysismentioning

confidence: 99%

“…Concentrations of organic ligands in the vicinity of the 79N Glacier terminus were high, but those ligands were relatively weak compared to organic ligands in Fram Strait and Norske Trough. In addition, it appears that the characteristics of organic ligands control the glacial DFe export from the northeast Greenland continental shelf to the Fram Strait (Ardiningsih et al, 2020;Krisch et al, 2020). Therefore, it is of interest to study whether the different methods will give the same information on ligand presence and environmental Fe transport in this region.…”

Section: Introductionmentioning

confidence: 99%

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Iron Speciation in Fram Strait and Over the Northeast Greenland Shelf: An Inter-Comparison Study of Voltammetric Methods

et al. 2021

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Competitive ligand exchange – adsorptive cathodic stripping voltammetry (CLE-AdCSV) is a widely used technique to determine dissolved iron (Fe) speciation in seawater, and involves competition for Fe of a known added ligand (AL) with natural organic ligands. Three different ALs were used, 2-(2-thiazolylazo)-p-cresol (TAC), salicylaldoxime (SA) and 1-nitroso-2-napthol (NN). The total ligand concentrations ([Lt]) and conditional stability constants (log K′Fe’L) obtained using the different ALs are compared. The comparison was done on seawater samples from Fram Strait and northeast Greenland shelf region, including the Norske Trough, Nioghalvfjerdsfjorden (79N) Glacier front and Westwind Trough. Data interpretation using a one-ligand model resulted in [Lt]SA (2.72 ± 0.99 nM eq Fe) > [Lt]TAC (1.77 ± 0.57 nM eq Fe) > [Lt]NN (1.57 ± 0.58 nM eq Fe); with the mean of log K′Fe’L being the highest for TAC (log ′KFe’L(TAC) = 12.8 ± 0.5), followed by SA (log K′Fe’L(SA) = 10.9 ± 0.4) and NN (log K′Fe’L(NN) = 10.1 ± 0.6). These differences are only partly explained by the detection windows employed, and are probably due to uncertainties propagated from the calibration and the heterogeneity of the natural organic ligands. An almost constant ratio of [Lt]TAC/[Lt]SA = 0.5 – 0.6 was obtained in samples over the shelf, potentially related to contributions of humic acid-type ligands. In contrast, in Fram Strait [Lt]TAC/[Lt]SA varied considerably from 0.6 to 1, indicating the influence of other ligand types, which seemed to be detected to a different extent by the TAC and SA methods. Our results show that even though the SA, TAC and NN methods have different detection windows, the results of the one ligand model captured a similar trend in [Lt], increasing from Fram Strait to the Norske Trough to the Westwind Trough. Application of a two-ligand model confirms a previous suggestion that in Polar Surface Water and in water masses over the shelf, two ligand groups existed, a relatively strong and relatively weak ligand group. The relatively weak ligand group contributed less to the total complexation capacity, hence it could only keep part of Fe released from the 79N Glacier in the dissolved phase.

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Section: Dfe and Fe-binding Ligand Analysissupporting

confidence: 61%

Section: Introductionmentioning

confidence: 91%