Evidence of organic matter control on As oxidation by iron oxides in riparian wetlands

Guénet, Hélène; Davranche, Mélanie; Vantelon, Delphine; Pédrot, Mathieu; Al-Sid-Cheikh, Maya; Dia, Aline; Jestin, Jacques

doi:10.1016/j.chemgeo.2016.06.023

Cited by 36 publications

(28 citation statements)

References 70 publications

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“…Arsenic was present as a mixture of As(III) and As(V). Guénet et al (2016) provided evidence that, in natural Fe-OM colloidal agglomerates, the OM prevents total As(III) oxidation by controlling the Fe species as Fe monomer/small clusters and weakly polymerized Fe(III) oxyhydroxides. The formation of these Fe species leads to the decrease of active adsorption sites for As oxidation.…”

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

confidence: 99%

“…They exhibited a shoulder at lower energy (close to 11872.3 eV), the intensity for which increased with the size fractionation. The shoulder and white line positions corresponded to a mixture of inorganic As (III) and As(V) (Guénet et al, 2016). The spectra for the < 30 kDa and < 5 kDa fractions exhibited a single peak species is prevented by the inability of XANES to discriminate between two aliphatic substituents on the C backbone (George and Pickering, 2007).…”

Section: Speciation Of Arsenic By X-ray Absorption Spectroscopymentioning

confidence: 99%

“…In previous studies, Al-Sid Cheikh et al (2015) and Guénet et al (2016), using a NanoSIMS analysis of agglomerate solids produced during the oxidizing period in our studied wetland, showed that the As distribution was highly heterogeneous with i) As associated with Fe-enriched zones and ii) As associated with OM-enriched/Fe-depleted hotspots. To explain this observed colocalization of As and OM, Al-SidCheikh et al (2015) suggested the binding of part of the As as As(III) to the OM thiol (SH-) functional groups.…”

Section: Implications For As Dynamics In Wetlandsmentioning

confidence: 99%

“…A proportion of this organic As(V) species was scavenged in plants and organisms although a second part was probably excreted and subsequently adsorbed to the Fe phases. The organic As(V) species in the residue from the organisms might explain the colocalization of As and OM observed by the NanoSIMS in the OM-enriched/Fe-depleted hotspots (Al-Sid Cheikh et al, 2015;Guénet et al, 2016).…”

Section: Implications For As Dynamics In Wetlandsmentioning

confidence: 99%

“…The formed solids are expected to settle in the soil porosity following the increase of evapotranspiration and the decrease of the water level. Al-Sid-Cheikh et al (2015) and Guénet et al (2016) studied similar agglomerates that were collected directly in a wetland soil matrix (Naizin Kervidy, France). They demonstrated that As was heterogeneously distributed in both Fe-enriched zones and OM-enriched/Fe depleted zones.…”

Section: Introductionmentioning

confidence: 99%

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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: 99%

Section: Speciation Of Arsenic By X-ray Absorption Spectroscopymentioning

confidence: 99%

Section: Implications For As Dynamics In Wetlandsmentioning

confidence: 99%

Section: Implications For As Dynamics In Wetlandsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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