Vivaspin ultrafiltration: A new approach for high resolution measurements of colloidal and soluble iron species

Schlösser, Christian; Streu, Peter; Croot, Peter

doi:10.4319/lom.2013.11.187

Cited by 11 publications

(8 citation statements)

References 48 publications

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“…Given the near 1:1 slope in relation to shipboard measurements, the excellent R 2 values, and the overlap between thawed 0.20 µm-filtered and thawed 0.02 µm-filtered samples, we conclude that freezing filtered samples is suitable for sample preservation. Moreover, the Mn(III)-L complexes we measured at this site are not operationally colloidal (size class between 20 to 200 nm), unlike Fe(III)-L species for which up to 90 % are found in the colloidal fraction (Schlosser et al, 2013). One possible interpretation of these results is that that Mn(III)-L species are more mobile and transported farther than their Fe(III)-L counterparts.…”

Section: Report Dissolved Organic Matter Concentrations ([Dom])mentioning

confidence: 74%

Soluble Mn(III)–L complexes are abundant in oxygenated waters and stabilized by humic ligands

Oldham

Mucci

Tebo

et al. 2017

Geochimica et Cosmochimica Acta

144

112

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Dissolved Mn (dMn T) is thought to be dominated by metastable Mn(II) in the presence of oxygen, as the stable form is insoluble Mn(IV). We show, for the first time, that Mn(III) is also stable as a soluble species in the oxygenated water column, when stabilized by organic ligands as Mn(III)-L complexes. We measured Mn(III)-L complexes in the oxygenated waters of a coastal fjord and a hemipelagic system where they make up to 86 % of the dMn T. Although Mn(III) forms similar complexes to Fe(III), unlike most of the analogous Fe(III)-L complexes, the Mn(III)-L complexes are not colloidal, as they pass through both 0.20 µm and 0.02 µm filters. Depending on the kinetic stability of the Mn(III) complexes and the microbial community of a given system, these Mn(III)-L complexes are capable of donating or accepting electrons and may therefore serve as both reductants or oxidants, can be biologically available, and can thus participate in a multitude of redox reactions and biogeochemical processes. Furthermore, sample acidification experiments revealed that Mn(III) binding to humic ligands is responsible for up to 100 % of this complexation, which can influence the formation of other metal complexes including Fe(III) and thus impact nutrient availability and uptake. Hence, humic ligands may play a greater role in dissolved Mn transport from coastal areas to the ocean than previously thought. 1.0 Introduction: Manganese (Mn) is ubiquitous in the global ocean, where it is an essential trace nutrient in the electron transfer processes of several metallo-enzymes-notably in photosystem II for photosynthetic organisms. In its solid oxidized form, it serves as an electron acceptor in the bacterial decomposition of sedimentary organic matter and acts as an important scavenger for 1 many trace elements and radionuclides. The chemical speciation of Mn in marine systems governs its diverse functions and is ultimately controlled by the redox conditions of the environment and the microbial community. The favorable oxidation state of Mn in oxic waters is Mn(IV), and thus Mn in oxygenated waters is primarily bound to oxygen as solid Mn(III/IV)oxides (MnO x). However, soluble Mn(II) is metastable in oxygenated waters because the oxidation of Mn(H 2 O) 6 2+ to MnO x by O 2 in an one electron transfer is thermodynamically unfavorable and the two electron transfer is kinetically slow (Luther 2010), unless facilitated by microbes, surface catalysis or superoxide-promotion (Stumm and Morgan, 1996). In the last decade, soluble manganese (dMn T) speciation has been re-evaluated to include soluble Mn(III) bound to ligands (Mn(III)-L complexes) in low oxygen environments. Mn(III)-L complexes have been measured in the suboxic porewaters of the St. Lawrence Estuary (Madison et al., 2013), the suboxic waters of the Black Sea (Yakushev et al., 2007, 2009; Trouwborst et al., 2006) and the Baltic Sea (Dellwig et al., 2012) as well as the anoxic bottom waters of the Chesapeake Bay (Trouwborst et al., 2006; Oldham et al., 2015). Because Mn(III)-L complexe...

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Section: Report Dissolved Organic Matter Concentrations ([Dom])mentioning

confidence: 74%

Soluble Mn(III)–L complexes are abundant in oxygenated waters and stabilized by humic ligands

Oldham

Mucci

Tebo

et al. 2017

Geochimica et Cosmochimica Acta

144

112

View full text Add to dashboard Cite

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“…5, 8b). At our study sites, 93% of dissolved Fe in the water column is aqueous Fe (< 0.02 μm) implying that Fe(III)-L plays a minor role (0.02-0.2 μm size fraction; Eckert and Sholkovitz (1976); Schlosser et al (2013); Oldham et al (2017a)). This suggests that upon precipitation, Fe oxides quickly aggregate to larger particles, in accordance with previous work (Boyle et al 1977;Lough et al 2019).…”

Section: Water Column Fe and Mn Dynamicsmentioning

confidence: 78%

Coastal hypoxia and eutrophication as key controls on benthic release and water column dynamics of iron and manganese

Lenstra

Hermans

Séguret

et al. 2020

Limnology & Oceanography

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Continental shelves are a major source of iron (Fe) and manganese (Mn) to marine waters. Here, we investigate controls on benthic release of Fe and Mn and the impact on the water column in the Baltic Sea. We find high in situ benthic release rates of dissolved Fe and Mn at seasonally hypoxic sites (bottom water oxygen between 0-63 μmol L −1) receiving high inputs of organic matter. We find that benthic Fe and Mn release is sensitive to bottom water oxygen concentrations. Benthic Fe release is likely additionally controlled by Fe-sulfur redox chemistry in the surface sediment. For Mn, benthic release correlates positively with Mn oxide availability in the surface sediment. Benthic release contributes to high dissolved Fe and Mn concentrations in the water column and is amplified by repeated cycling of Fe and Mn between the sediment and overlying water through benthic release, oxidation in the water column, deposition as metal oxides, followed by reductive dissolution. Most water column Fe ($ 80%) is present in particulate form near the seafloor. In contrast to Fe, a large percentage of the Mn remains dissolved ($ 50%). We show that easily reducible Fe and Mn oxides are key forms of particulate Fe and Mn in suspended matter. The Baltic Sea represents a highly eutrophic, low oxygen end-member when compared to other modern coastal systems. Our results imply that, upon continued eutrophication and deoxygenation of the coastal ocean, benthic release of dissolved Fe and Mn from continental shelves could become greater than previously thought.

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“…As can be seen in Figure , the percent of dFe observed in the <0.02 µm soluble fraction increased to 60% in the ODZ, relative to the 40–50% soluble Fe above and below, consistent with a hypothesis of additional soluble‐sized Fe(II) delivery to the ODZ dFe layer. However, these physical speciation data do not preclude that this additional soluble Fe is in the Fe(III) oxidation state, such as would be the case if additional soluble‐sized organic Fe(III)‐binding ligands [ Fitzsimmons et al , ; Schlosser et al , ] were supplied from the shelf, though to date benthic ligand sources have been shown to supply weaker ligands of humic composition [ Bundy et al , ], which would rather fall in the colloidal size fraction.…”

Section: Resultsmentioning

confidence: 99%

Dissolved iron and iron isotopes in the southeastern Pacific Ocean

Fitzsimmons

Conway

Lee

et al. 2016

Global Biogeochemical Cycles

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The Southeast Pacific Ocean is a severely understudied yet dynamic region for trace metals such as iron, since it experiences steep redox and productivity gradients in upper waters and strong hydrothermal iron inputs to deep waters. In this study, we report the dissolved iron (dFe) distribution from seven stations and Fe isotope ratios (δ 56 Fe) from three of these stations across a near-zonal transect from 20 to 27°S. We found elevated dFe concentrations associated with the oxygen-deficient zone (ODZ), with light δ 56 Fe implicating porewater fluxes of reduced Fe. However, temporal dFe variability and rapid δ 56 Fe shifts with depth suggest gradients in ODZ Fe source and/or redox processes vary over short-depth/spatial scales. The dFe concentrations decreased rapidly offshore, and in the upper ocean dFe was controlled by biological processes, resulting in an Fe:C ratio of 4.2 μmol/mol. Calculated vertical diffusive Fe fluxes were greater than published dust inputs to surface waters, but both were orders of magnitude lower than horizontal diffusive fluxes, which dominate dFe delivery to the gyre. The δ 56Fe data in the deep sea showed evidence for a À0.2‰ Antarctic Intermediate Water end-member and a heavy δ

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Vivaspin ultrafiltration: A new approach for high resolution measurements of colloidal and soluble iron species

Cited by 11 publications

References 48 publications

Soluble Mn(III)–L complexes are abundant in oxygenated waters and stabilized by humic ligands

Soluble Mn(III)–L complexes are abundant in oxygenated waters and stabilized by humic ligands

Coastal hypoxia and eutrophication as key controls on benthic release and water column dynamics of iron and manganese

Dissolved iron and iron isotopes in the southeastern Pacific Ocean

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