Metal speciation from stream to open ocean: modelling v. measurement

Tipping, Edward; Lofts, Stephen; Stockdale, Anthony

doi:10.1071/en15111

Cited by 29 publications

(15 citation statements)

References 94 publications

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“…(1.62-2.52 kDa) were reported for colloidal DOM in Chukchi Sea (Lin et al, 2016). The average MW reported in Beaufort Sea agreed with values reported for fulvic acids (Beckett et al, 1987;Guéguen and Cuss, 2011), confirming that fulvic acids are good proxy for marine DOM (Tipping et al, 2015).…”

Section: Molecular Weight Depth Distributionsupporting

confidence: 78%

Size distribution of absorbing and fluorescing DOM in Beaufort Sea, Canada Basin

Gao

Guéguen

2017

Deep Sea Research Part I: Oceanographic Research Papers

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The molecular weight (MW) of dissolved organic matter (DOM) is considered as an important factor affecting the bioavailability of organic matter and associated chemical species. Colored DOM (CDOM) MW distribution was determined, for the first time, in the Beaufort Sea (Canada Basin) by asymmetrical flow field-flow fractionation (AF4) coupled with online diode array ultra violet-visible photometer and offline fluorescence detectors. The apparent MW ranged from 1.07 kDa to 1.45 kDa, congruent with previous studies using high performance size exclusion chromatography and tangential flow filtration. Interestingly, a minimum in MW was associated with the Pacific Summer Waters (PSW), while higher MW was associated with the Pacific Winter Waters (PWW). The Arctic Intermediate Waters (AIW) did not show any significant change in MW and fluorescence intensities distribution between stations, suggesting homogeneous DOM composition in deep waters. Three fluorescence components including two humic-like components and one protein-like component were PARAFAC-validated. With the increase of MW, protein-like fluorescence component became more dominant while the majority remained as marine/microbially derived humic-like components. Overall, it is concluded that water mass origin influenced DOM MW distribution in the Arctic Ocean.

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Section: Molecular Weight Depth Distributionsupporting

confidence: 78%

Size distribution of absorbing and fluorescing DOM in Beaufort Sea, Canada Basin

Gao

Guéguen

2017

Deep Sea Research Part I: Oceanographic Research Papers

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“…The NICA-Donnan approach is one of a suite of modeling approaches (Dudal and Gérard, 2004;Tipping, 2005;Stockdale et al, 2015;Tipping et al, 2015) that attempts to represent the complexity of metal complexation with DOM in a way which is independent of pH, ionic strength and the presence of competing cations. In the NICA-Donnan model, DOM is considered to behave like humic or fulvic acids Koopal et al, 2005).…”

Section: Modeling Iron and Copper Complexation By Dissolved Organic Mmentioning

confidence: 99%

Influence of Ocean Acidification on the Organic Complexation of Iron and Copper in Northwest European Shelf Seas; a Combined Observational and Model Study

et al. 2016

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The pH of aqueous solutions is known to impact the chemical speciation of trace metals. In this study we conducted titrations of coastal seawaters with iron and copper at pH 7.91, 7.37, and 6.99 (expressed on the total pH scale). Changes in the concentration of iron and copper that complexed with the added ligands 1-nitroso-2-napthol and salicylaldoxime respectively were determined by adsorptive cathodic stripping voltammetry-competitive ligand equilibrium (AdCSV-CLE). Interpretation of the results, assuming complexation by a low concentration of discrete ligands, showed that conditional stability constants for iron complexes increased relative to inorganic iron complexation as pH decreased by approximately 1 log unit per pH unit, whilst those for copper did not change. No trend was observed for concentrations of iron and copper complexing ligands over the pH range examined. We also interpreted our titration data by describing chemical binding and polyelectrolytic effects using non-ideal competitive adsorption in Donnan-like gels (NICA-Donnan model) in a proof of concept study. The NICA-Donnan approach allows for the development of a set of model parameters that are independent of ionic strength and pH, and thus calculation of metal speciation can be undertaken at ambient sample pH or the pH of a future, more acidic ocean. There is currently a lack of basic NICA-Donnan parameters applicable to marine dissolved organic matter (DOM) so we assumed that the measured marine dissolved organic carbon could be characterized as terrestrial fulvic acids. Generic NICA-Donnan parameters were applied within the framework of the software program visual MINTEQ and the metal-added ligand concentrations [MeAL] calculated for the AdCSV-CLE conditions. For copper, calculated [MeAL] using the NICA-Donnan model for DOM were consistent with measured [MeAL], but for iron an inert fraction with kinetically inhibited dissolution was required in addition to the NICA-Donnan model in order to approximate the trends observed in measured [MeAL]. We calculated iron and copper speciation in Northwest European shelf water samples at ambient alkalinity and projected increased pCO 2 concentrations as a demonstration of the potential of the approach.

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“…Dissolved metal-organic complexes are important in many natural waters and can be the dominant form of dissolved metals in some systems (e.g., Mantoura et al, 1978;Tipping et al, 2015). These dissolved metal complexes will compete with adsorbed solid-surface complexes for the heavier Zn isotopes (Jovin et al, 2009).…”

Section: Biogeochemical Fractionation Of Zn Isotopesmentioning

confidence: 99%

Isotope variations of dissolved Zn in the Rio Grande watershed, USA: The role of adsorption on Zn isotope composition

Szynkiewicz

Borrok

2016

Earth and Planetary Science Letters

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In order to better understand the factors influencing zinc (Zn) isotope composition in hydrological systems, we analyzed the δ 66 Zn of dissolved Zn in the streams and groundwater of the Upper and Middle Rio Grande watershed in Colorado and New Mexico, United States. The stream water samples have a wider variation of δ 66 Zn (-0.57 to +0.41 ‰ relative to the JMC 3-0749-Lyon standard) than groundwater samples (-0.13 to +0.12 ‰) and than samples from streams that are in close proximity to abandoned mining sites (+0.24 to +0.40 ‰). Regional changes of bedrock geology, from primarily igneous rocks to primarily sedimentary rocks, have no resolvable effect on the δ 66 Zn of aqueous samples. Instead, an increase in water pH from 7.5 to 8.5 corresponds to a considerable decrease in the δ 66 Zn of dissolved Zn (R 2 =-0.37, p=0.003, n=22). Consequently, we link the observed Zn isotope variations to the process of adsorption of Zn onto suspended sediment and bedrock minerals (average  66 Zn adsorbed-dissolved = +0.31‰). Our results are in good agreement with previous experimental and empirical studies suggesting that Zn adsorption leads to a residual dissolved pool enriched in light Zn isotopes. Given that anthropogenic Zn sources can also be responsible for lowering of δ 66 Zn, and may overlap with the pH/adsorption effect on δ 66 Zn, the latter needs to be carefully considered in future studies to differentiate between natural and anthropogenic factors influencing Zn isotopes in this and other aquatic systems.

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Metal speciation from stream to open ocean: modelling v. measurement

Cited by 29 publications

References 94 publications

Size distribution of absorbing and fluorescing DOM in Beaufort Sea, Canada Basin

Size distribution of absorbing and fluorescing DOM in Beaufort Sea, Canada Basin

Influence of Ocean Acidification on the Organic Complexation of Iron and Copper in Northwest European Shelf Seas; a Combined Observational and Model Study

Isotope variations of dissolved Zn in the Rio Grande watershed, USA: The role of adsorption on Zn isotope composition

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