Small changes in Cu redox state and speciation generate large isotope fractionation during adsorption and incorporation of Cu by a phototrophic biofilm

Coutaud, Margot; Méheut, Merlin; Glatzel, Pieter; Pokrovski, Gleb S.; Viers, Jérôme; Rols, Jean‐Luc; Pokrovsky, Oleg S.

doi:10.1016/j.gca.2017.09.018

Cited by 29 publications

(32 citation statements)

References 109 publications

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“…During our sampling period, the temperature was low (13.6e17.1 C, upstream) and we did not detect any algal bloom that could have affected the dissolved Cu. Moreover, the uptake of Cu by bacteria, peryphytic biofilm or algae favors the light Cu isotope into the biomass (Navarrete et al, 2011;Coutaud et al, 2018). This process would enrich the river water in heavy isotope, which is not consistent with our observations.…”

Section: Variations Of Cu Concentration and Isotopic Composition At Tcontrasting

confidence: 90%

Strong temporal and spatial variation of dissolved Cu isotope composition in acid mine drainage under contrasted hydrological conditions

Masbou

Viers

Grande

et al. 2020

Environmental Pollution

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Copper export and mobility in acid mine drainage are difficult to understand with conventional approaches. Within this context, Cu isotopes could be a powerful tool and here we have examined the relative abundance of dissolved (<0.22 mm) Cu isotopes (d 65 Cu) in the Meca River which is an outlet of the Tharsis mine, one of the largest abandoned mines of the Iberian Pyrite Belt, Spain. We followed the chemical and isotopic composition of the upstream and downstream points of the catchment during a 24-h diel cycle. Additional d 65 Cu values were obtained from the tributary stream, suspended matter (>0.22 mm) and bed sediments samples. Our goals were to 1) assess Cu sources variability at the upstream point under contrasted hydrological conditions and 2) investigate the conservative vs. non conservative Cu behavior along a stream. Average d 65 Cu values varied from À0.47 to À0.08‰ (n ¼ 9) upstream and from À0.63 to À0.31‰ downstream (n ¼ 7) demonstrating that Cu isotopes are heterogeneous over the diel cycle and along the Meca River. During dry conditions, at the upstream point of the Meca River the Cu isotopic composition was heavier which is in agreement with the preferential release of heavy isotopes during the oxidative dissolution of primary sulfides. The more negative values obtained during high water flow are explained by the contribution of soil and waste deposit weathering. Finally, a comparison of upstream vs. downstream Cu isotope composition is consistent with a conservative behavior of Cu, and isotope mass balance calculations estimate that 87% of dissolved Cu detected downstream originate from the Tharsis mine outlet. These interpretations were supported by thermodynamic modelling and sediment characterization data (X-ray diffraction, Raman Spectroscopy). Overall, based on contrasted hydrological conditions (dry vs flooded), and taking the advantage of isotope insensitivity to dilution, the present work demonstrates the efficiency of using the Cu isotopes approach for tracing sources and processes in the AMD regions.

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Section: Variations Of Cu Concentration and Isotopic Composition At Tcontrasting

confidence: 90%

Strong temporal and spatial variation of dissolved Cu isotope composition in acid mine drainage under contrasted hydrological conditions

Masbou

Viers

Grande

et al. 2020

Environmental Pollution

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“…Thus, the rather small 65 Cu sw-fmc offset presents a paradox, suggesting that Cu in Fe-Mn crusts is out of isotopic equilibrium with deep seawater -a surprising finding. It is possible that natural organic Cu ligands in seawater are not associated with isotope fractionation, but we consider this unlikely, given the lines of experimental and theoretical evidence suggesting otherwise (Bigalke et al, 2010;Ryan et al, 2014;Sherman, 2013;Sherman et al, 2015;Fujii et al, 2013).…”

Section: Application To the Oceansmentioning

confidence: 99%

“…However, an important difference between biooxides and inorganic δ-MnO 2 may be the presence of extracellular polymeric substances (EPS) produced by Mn(II) oxidising bacteria, which can affect the sorptive properties of the biooxide (Tebo et al, 2004). The presence of EPS may also influence the isotopic fractionation associated with Cu sorption (Coutaud et al, 2018), even if the ultimate mineral binding site of the Cu is apparently unaffected (Little et al, 2014a).…”

Section: Application To the Oceansmentioning

confidence: 99%

Isotopic disequilibrium of Cu in marine ferromanganese crusts: Evidence from ab initio predictions of Cu isotope fractionation on sorption to birnessite

Sherman

Little

2020

Earth and Planetary Science Letters

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In the oceans, Cu is strongly scavenged by ferromanganese (Fe-Mn) crusts. The isotopic fractionation of Cu between seawater and crusts provides insight into the mechanisms of trace metal cycling in the oceans. Dissolved Cu in seawater is isotopically heavy (+0.66 ± 0.19 ) relative to Cu in crusts (+0.31 ± 0.24 ). The primary mineral phase sorbing divalent trace metals in Fe-Mn crusts is birnessite. Recent laboratory measurements show that isotopically light Cu is preferentially sorbed on birnessite, with a fractionation factor of 0.45 ± 0.18 . Here, we use first-principles (quantum mechanical) calculations to predict the isotopic fractionation between aqueous Cu 2+ complexes and Cu as a surface complex on birnessite. We find that isotopic fractionation between the Cu(H 2 O) +5 complex and sorbed Cu should be 0.49 (at 25 • C), in close agreement with experiments, confirming that these experimental results reflects equilibrium fractionation. We then predict the isotopic fractionation between dissolved inorganic Cu in seawater and birnessite given the thermodynamic speciation of dissolved Cu at pH 8. We find dissolved inorganic Cu should be 0.94 (at 5 • C) heavier than Cu sorbed to birnessite. This value is substantially greater than the observed fractionation between seawater and Fe-Mn crusts ( sw-fmc ≈ +0.35 ). Moreover, it is well established that dissolved Cu in seawater is strongly complexed by organic ligands. Based on model Cu complexes and published experimental data, we estimate that fractionation of Cu by organic ligands should increase the equilibrium fractionation between seawater and Fe-Mn crusts by 0.2 to 1.5 to yield sw-fmc = +1.1 to 2.4 . We conclude that Cu in marine Fe-Mn crusts in not in isotopic equilibrium with dissolved Cu in seawater, and consider the possible explanations of this surprising finding.

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“…Weathering of the continents supplies solutes to rivers, which constitute a key input of Zn and Cu to the modern ocean (Little et al, 2014b). The Zn and Cu isotope composition of rivers will thus reflect that supplied by weathering, though biogeochemical processes in rivers may subsequently modify this primary signature (e.g., Borrok et al, 2008;Coutaud et al, 2014;Szynkiewicz and Borrok, 2016;Coutaud et al, 2018). The aim of this study is to investigate Zn and Cu isotope fractionation during extreme chemical weathering.…”

Section: Introductionmentioning

confidence: 99%

Cu and Zn isotope fractionation during extreme chemical weathering

Little

Munson

Prytulak

et al. 2019

Geochimica et Cosmochimica Acta

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show abstract

Small changes in Cu redox state and speciation generate large isotope fractionation during adsorption and incorporation of Cu by a phototrophic biofilm

Cited by 29 publications

References 109 publications

Strong temporal and spatial variation of dissolved Cu isotope composition in acid mine drainage under contrasted hydrological conditions

Strong temporal and spatial variation of dissolved Cu isotope composition in acid mine drainage under contrasted hydrological conditions

Isotopic disequilibrium of Cu in marine ferromanganese crusts: Evidence from ab initio predictions of Cu isotope fractionation on sorption to birnessite

Cu and Zn isotope fractionation during extreme chemical weathering

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