Arsenite Binding to Natural Organic Matter: Spectroscopic Evidence for Ligand Exchange and Ternary Complex Formation

Hoffmann, M.; Mikutta, Christian; Kretzschmar, Ruben

doi:10.1021/es4023317

Cited by 79 publications

(82 citation statements)

References 64 publications

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“…However, the As K-edge EXAFS spectra showed that part of the As was bound to Fe as monodentate binuclear corner-sharing complexes ( 2 C) on the small Fe clusters. Considering the Fe-C distance of 2.8 Å as well as the As-Fe distance of 3.43 Å, ternary complexes were possibly formed in the LMW fractions (Mikutta and Kretzschmar, 2011;Sharma et al, 2011;Hoffmann et al, 2013), which was confirmed by the coelution of Fe, As and OM in the SEC-ICP-MS analysis.…”

Section: µM-30 Kda Fraction This Size Fraction Represented the Most mentioning

confidence: 68%

Highlighting the wide variability in arsenic speciation in wetlands: A new insight into the control of the behavior of arsenic

Guénet

Davranche

Vantelon

et al. 2017

Geochimica et Cosmochimica Acta

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Highlighting the wide variability in arsenic speciation in wetlands: a new insight into the control of the behavior of arsenic. Geochimica et Cosmochimica Acta, Elsevier, 2017, 203, pp.284-302 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 1Highlighting the wide variability in arsenic speciation in wetlands: AbstractAlthough the behavior of Arsenic (As) under reducing conditions in periods of high water levels in wetlands is well understood and documented, there is a lack of information under oxidizing conditions when the water level decreases. In this study, we were interested in the first stage of the oxidizing period, when oxidation products are still in suspension. A soil sample from the Naizin Kervidy wetland (France) was incubated in the laboratory to produce a reduced soil solution. The reduced solution was subsequently oxidized, filtered and ultrafiltered using decreasing pore size membranes (5 µm, 3 µm, 0.2 µm, 30 kDa and 5 kDa). The distribution of As and Fe was investigated in each size fraction of the oxidized solution and their speciations were studied using XAS, HPLC and SEC-ICP-MS. Organic matter was characterized using thermally assisted hydrolysis and methylation gas chromatography-mass spectrometry (THM-GC-MS) and fluorescence spectroscopy. The majority of the As was present as As(V) but a small amount of As(III) still remained despite the advanced oxidized conditions. In the > 0.2 µm fractions, the XAS analyses showed that As was associated, in the second shell, with Fe (As-Fe = 3.35 Å) as bidentate binuclear complexes and C (As-C = 2.90 Å), suggesting the integration of As in biological objects. In the < 30 kDa fraction, As was directly bound to C (As-C = 1.96 Å) in the first shell indicating the presence of organic As species. In the second shell, an As-Fe distance of 3.35 Å was found showing that 2 part of the As was still complexed with Fe. The 0.2 µm-30 kDa fraction was a transitional fraction in terms of the Fe species and OM composition. In this fraction, organic matter exhibited a more humic character (aromatic molecules) inducing an increasing cation binding capacity. As a consequence, in this fraction and in the smallest one, As, Fe and OM seemed to form ternary complexes in which the Fe or nano-oxides in the > 30 kDa fraction and as monomer, or cluster in < 30 kDa fraction acted as a bridge. In all of the fractions, a proportion of As(V) was present as organic methylated species. These organic species might be produced by several organisms (animal or plant) via a detoxification process. They seemed to be bound to the particulate and colloidal Fe/OM phases as well as integ...

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Section: µM-30 Kda Fraction This Size Fraction Represented the Most mentioning

confidence: 68%

Highlighting the wide variability in arsenic speciation in wetlands: A new insight into the control of the behavior of arsenic

Guénet

Davranche

Vantelon

et al. 2017

Geochimica et Cosmochimica Acta

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“…Different mechanisms were put forward to describe As-OM binding, including As(III, V) complexation with OM carboxylic and phenolic groups [17,18], or As(III) binding with OM thiol groups [19][20][21]. However, most of the As bound to OM generally occurs as As-Fe-OM ternary complexes in several systems, such as peatland, riparian wetlands, streams, groundwaters [13,[22][23][24][25][26][27]. The high affinity of As for Fe(III)-oxyhydroxides and of Fe(III)/Fe(III)-oxyhydroxides for OM explains this behavior [14,23,25,[28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Does As(III) interact with Fe(II), Fe(III) and organic matter through ternary complexes?

Catrouillet

Davranche

Dia

et al. 2016

Journal of Colloid and Interface Science

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Up until now, only a small number of studies have been dedicated to the binding processes of As(III) with organic matter (OM) via ionic Fe(III) bridges; none was interested in Fe (II). Complexation isotherms were carried out with As(III), Fe(II) or Fe(III) and Leonardite humic acid (HA). Although PHREEQC/Model VI, implemented with OM thiol groups, reproduced the experimental datasets with Fe(III), the poor fit between the experimental and modeled Fe(II) data suggested another binding mechanism for As(III) to OM. PHREEQC/Model VI was modified to take various possible As(III)-Fe(II)-OM ternary complex conformations into account. The complexation of As(III) as a mononuclear bidentate complex to a bidentate Fe(II)-HA complex was evidenced. However, the model needed to be improved since the distribution of the bidentate sites appeared to be unrealistic with regards to the published XAS data. In the presence of Fe(III), As(III) was bound to thiol groups which are more competitive with regards to the low density of formed Fe(III)-HA complexes. Based on the new data and previously published results, we propose a general scheme describing the various As(III)-Fe-MO complexes that are able to form in Fe and OM-rich waters.

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“…Organic matter also competes with As(III/V) for binding sites at mineral surfaces (Xu et al, 1991;Grafe et al, 2001Grafe et al, , 2002Redman et al, 2002;Simeoni et al, 2003;Bauer and Blodau, 2006) and there are studies suggesting formation of As-OM complexes (Redman et al, 2002;Buschmann et al, 2006). These interactions between As and OM are believed to occur mainly via Fe-bridges in ternary ironarsenate complexes (Lin et al, 2004;Redman et al, 2002;Sharma et al, 2010Sharma et al, , 2011Hoffmann et al, 2013). In most cases this interpretation is based on indirect evidence such as correlations between concentrations of As, Fe and/or OM (Dobran and Zagury, 2006;Ritter et al, 2006;Rothwell et al, 2009) or on results from sequential extraction procedures (González et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Complexation and precipitation reactions in the ternary As(V)–Fe(III)–OM (organic matter) system

Sundman

Karlsson

Sjöberg

et al. 2014

Geochimica et Cosmochimica Acta

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The predominant forms of arsenic (As) in anoxic and oxic environments are As(III) and As(V), respectively, and the fate of these forms is influenced by interactions with mineral surfaces and organic matter (OM). Interactions between As(V) and OM are believed to occur mainly via iron(Fe)-bridges in ternary Fe-arsenate complexes, but direct evidence for these interactions are scarce. Furthermore, since the speciation of Fe in the presence of organic matter varies as a function of pH and Fe concentration, a central question is how different chemical conditions will affect the As-Fe-OM interactions. In order to answer this, the As(V)-Fe(III)-OM system have been studied under a large range of experimental conditions (6485-67,243 ppm Fe(III) and Fe(III):As(V) ratios of 0.5-20 at pH 3-7), with Suwannee River natural organic matter and Suwannee River fulvic acid as sources of OM, using Fe and As K-edge X-ray absorption spectroscopy (XAS), infrared (IR) spectroscopy and chemical equilibrium modeling. Our collective results showed that interactions in the ternary As(V)-Fe(III)-OM system were strongly influenced by pH, total concentrations and ratios among the reactive species. In particular, the high stability of the Fe(III)-OM complexes exerted a strong control on the speciation. The predominant species identified were mononuclear Fe(III)-OM complexes, Fe(III) (hydr)oxides and FeAsO 4 solids. The experimental results also showed that at low concentrations the Fe(III)-OM complexes were sufficiently stable to prevent reaction with arsenate. The chemical equilibrium models developed corroborated the spectroscopic results and indicated that As(V) was distributed over two solid phases, namely FeAsO 4 (s) and Fe(OH) 1.5 (AsO 4 ) 0.5 (s). Thus, neither ternary As(V)-Fe(III)-OM complexes nor As(V) surface complexes on Fe(III) (hydr)oxides were necessary to explain the collective results presented in this study.

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Arsenite Binding to Natural Organic Matter: Spectroscopic Evidence for Ligand Exchange and Ternary Complex Formation

Cited by 79 publications

References 64 publications

Highlighting the wide variability in arsenic speciation in wetlands: A new insight into the control of the behavior of arsenic

Highlighting the wide variability in arsenic speciation in wetlands: A new insight into the control of the behavior of arsenic

Does As(III) interact with Fe(II), Fe(III) and organic matter through ternary complexes?

Complexation and precipitation reactions in the ternary As(V)–Fe(III)–OM (organic matter) system

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