An Intercomparison of Dissolved Iron Speciation at the Bermuda Atlantic Time-series Study (BATS) Site: Results from GEOTRACES Crossover Station A

Buck, Kristen N.; Gerringa, Loes J. A.; Rijkenberg, Micha J.A.

doi:10.3389/fmars.2016.00262

Cited by 20 publications

(27 citation statements)

References 58 publications

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“…The pH at which the SA method was applied (8.4) was higher than the pH of 8.05 used in the TAC method but was necessary to avoid peak interferences and low sensitivity. This obviously has consequences, as also described by Buck et al (, ). They compared both methods using pH of 8 and 8.05, respectively, for the TAC method and a pH of 8.2 for the SA method.…”

Section: Discussionmentioning

confidence: 58%

Fe‐Binding Organic Ligands in the Humic‐Rich TransPolar Drift in the Surface Arctic Ocean Using Multiple Voltammetric Methods

et al. 2019

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Samples inside and outside the Arctic Ocean's TransPolar Drift (TPD) have been analyzed for Fe‐binding organic ligands (Lt) with Competitive Ligand Exchange Adsorptive Stripping Voltammetry (CLE‐AdCSV) using salicylaldoxime (SA). This analysis is compared to prior analyses with CLE‐AdCSV using 2‐(2‐thiazolylazo)‐p‐cresol (TAC). The TPD's strong terrestrial influence is used to compare the performance of both CLE‐AdCSV methods in representing the nature of natural organic ligands. These measurements are compared against direct voltammetric determination of humic substances (HS) and spectral properties of dissolved organic matter. The relationship between the two CLE‐AdCSV derived [Lt] versus HS in the TPD has a comparable slope, with a 40% offset toward higher values obtained with SA. Higher [Lt] values inside the TPD, most probably due to HS, explain high dissolved Fe concentrations transported over the Arctic Ocean by the TPD. Outside of the TPD in the surface Arctic Ocean HS occur as well but at lower concentrations. Here changes in HS relate to changes in dissolved Fe concentration and to [Lt] obtained with SA, whereas [Lt] obtained with TAC remain constant. Moreover, with decreasing HS the offset between the methods using TAC and SA decreases. We surmise that in the presence of HS, the TAC method detects HS only either at higher concentrations or of specific composition. On the other hand, the SA method might overestimate [Lt], as an offset with the TAC method that remains constant where HS are not detected. Regardless, HS are the dominant type of Fe‐binding organic ligand in the surface of the Arctic Ocean.

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Section: Discussionmentioning

confidence: 58%

Fe‐Binding Organic Ligands in the Humic‐Rich TransPolar Drift in the Surface Arctic Ocean Using Multiple Voltammetric Methods

et al. 2019

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“…Because the Mediterranean Sea is surrounded by continents and the main Mediterranean rivers are located in the Western Basin, HS could play an important role in the complexation of DFe in this basin. Based on the relatively low conditional stability constants (10.6 ± 0.2 ≤ log K ' FeHS ≤ 11.1 ± 0.2) of humic‐type ligands for iron complexation determined by Laglera and van den Berg () using SRFA and SRHA as model, humics are generally considered as a weaker class of ligands (L 2 ) than siderophores (L 1 , log K ′ FeL1 > 12; Buck et al, ; Rijkenberg et al, ). Then humics, assumed to be relatively weak, become important for the biogeochemical cycle of Fe when the relatively stronger ligands are saturated.…”

Section: Resultsmentioning

confidence: 99%

The Biogeochemistry of Electroactive Humic Substances and Its Connection to Iron Chemistry in the North East Atlantic and the Western Mediterranean Sea

et al. 2018

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We present the zonal distribution of electroactive humic‐like substances (eHS) along a section from Offshore Portugal in the North East Atlantic to the Sicily Channel in the Mediterranean Sea. The concentrations were normalized to Suwannee River Fulvic Acid and ranged from 11 μg/L to 81 μg/L. The vertical distributions were typical of those previously reported for dissolved organic carbon in the Mediterranean Sea. High eHS concentrations were measured in surface water and concentrations decreased with depth before increasing again toward benthic maxima measured at some stations. We estimate that eHS represented a relatively small fraction of the natural organic matter in the Mediterranean Sea (2–5%) but considering their important role in the complexation and the solubility of key trace elements (e.g., iron and copper), the eHS cycle could influence the entire biogeochemistry of these marine systems. We identified key processes controlling the concentration of eHS. While biologically mediated production was the major source of eHS, riverine and rain inputs as well as sediment release were also likely external sources. Low eHS concentrations at subsurface depths pointed to photodegradation as a possible sink of eHS, but degradation by heterotrophic bacteria seemed to be the main sink in the deep sea. Finally, we found a positive correlation between dissolved iron and eHS concentrations. Estimation of eHS contribution to iron binding ligand concentrations indicates the complexation of iron by eHS in the Mediterranean Sea. These observations suggest links between the cycles of eHS and iron in the Mediterranean Sea.

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“…Dissolved Fe(II) can be determined by flow injection analysis with in-line preconcentration and chemiluminescence detection. DFe can be determined by flow injection analysis with in-line preconcentration on chelating resin followed by analysis using colorimetric technique or IC-PMS (Biller and Bruland, 2012;Rijkenberg et al, 2014;Sedwick et al, 2015;Buck et al, 2016;Wuttig et al, 2019).…”

Section: Standardization Of Aerosol Fe Measurementsmentioning

confidence: 99%

Perspective on identifying and characterizing the processes controlling iron speciation and residence time at the atmosphere-ocean interface

et al. 2019

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It is well recognized that the atmospheric deposition of iron (Fe) affects ocean productivity, atmospheric CO 2 uptake, ecosystem diversity, and overall climate. Despite significant advances in measurement techniques and modeling efforts, discrepancies persist between observations and models that hinder accurate predictions of processes and their global effects. Here, we provide an assessment report on where the current state of knowledge is and where future research emphasis would have the highest impact in furthering the field of Fe atmosphere-ocean biogeochemical cycle. These results were determined through consensus reached by diverse researchers from the oceanographic and atmospheric science communities with backgrounds in laboratory and in situ measurements, modeling, and remote sensing. We discuss i) novel measurement methodologies and instrumentation that allow detection and speciation of different forms and oxidation states of Fe in deliquesced mineral aerosol, cloud/rainwater, and seawater; ii) oceanic models that treat Fe cycling with several external sources and sinks, dissolved, colloidal, particulate, inorganic, and organic ligand-complexed forms of Fe, as well as Fe in detritus and phytoplankton; and iii) atmospheric models that consider natural and anthropogenic sources of Fe, mobilization of Fe in mineral aerosols due to the dissolution of Fe-oxides and Fe-substituted aluminosilicates through proton-promoted, organic ligand-promoted, and photo-reductive mechanisms. In addition, the study identifies existing challenges and disconnects (both fundamental and methodological) such as i) inconsistencies in Fe nomenclature and the definition of bioavailable Fe between oceanic and atmospheric disciplines, and ii) the lack of characterization of the processes controlling Fe speciation and residence time at the atmosphere-ocean interface. Such challenges are undoubtedly caused by extremely low concentrations, short lifetime, and the myriad of physical, (photo)chemical, and biological processes affecting global biogeochemical cycling of Fe. However, we also argue that the historical division (separate treatment of Fe biogeochemistry in oceanic and atmospheric disciplines) and the classical funding structures (that often create obstacles for transdisciplinary collaboration) are also hampering the advancement of knowledge in the field. Finally, the study

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An Intercomparison of Dissolved Iron Speciation at the Bermuda Atlantic Time-series Study (BATS) Site: Results from GEOTRACES Crossover Station A

Cited by 20 publications

References 58 publications

Fe‐Binding Organic Ligands in the Humic‐Rich TransPolar Drift in the Surface Arctic Ocean Using Multiple Voltammetric Methods

Fe‐Binding Organic Ligands in the Humic‐Rich TransPolar Drift in the Surface Arctic Ocean Using Multiple Voltammetric Methods

The Biogeochemistry of Electroactive Humic Substances and Its Connection to Iron Chemistry in the North East Atlantic and the Western Mediterranean Sea

Perspective on identifying and characterizing the processes controlling iron speciation and residence time at the atmosphere-ocean interface

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