Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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    We will mail you new results for this query: keywords==exafs spectroscopy
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Characterization of colloidal Fe from soils using field-flow fractionation and Fe K-edge X-ray absorption spectroscopy
Regelink, I.C. ; Voegelin, A. ; Weng, L. ; Koopmans, G.F. ; Comans, R.N.J. - \ 2014
Environmental Science and Technology 48 (2014)8. - ISSN 0013-936X - p. 4307 - 4316.
iron-oxide nanoparticles - natural organic-matter - acid forest soils - exafs spectroscopy - mineral nanoparticles - trace-metals - speciation - surface - ferrihydrite - associations
Colloids may facilitate the transport of trace elements and nutrients like phosphate in soil. In this study, we characterized soil colloids (
Surface speciation of As(III) en As(V) in relation to charge distribution
Stachowicz, M. ; Hiemstra, T. ; Riemsdijk, W.H. van - \ 2006
Journal of Colloid and Interface Science 302 (2006)1. - ISSN 0021-9797 - p. 62 - 75.
goethite-water interface - x-ray-absorption - density-functional calculations - exafs spectroscopy - alpha-feooh - adsorption mechanisms - 2-line ferrihydrite - sulfate adsorption - crystal-structure - pb(ii) sorption
The adsorption of As(III) and As(V) on goethite has been studied as a function of pH and loading. The data can be successfully described with the charge distribution (CD) model (extended Stern layer option) using realistic species observed by EXAFS. The CD values have been derived theoretically. Therefore, the Brown bond valence approach has been applied to MO/DFT optimized geometries of a series of hydrated complexes of As(III) and As(V) with Fe(III) (hydr)oxide. The calculated ionic CD values have been corrected for the effect of dipole orientation of interfacial water, resulting in overall interfacial CD coefficients that can be used to describe the surface speciation as a function of pH and loading. For As(III), the main surface species is a bidentate complex and a minor contribution of a monodentate species is found, which is in agreement with EXAFS. The CD values have also been fitted. Such an analysis of the adsorption data resulted in the same surface species. The fitted CD values for the bidentate complex points to the presence of strong AsO bonds with the surface and a weaker AsOH bond with the free OH ligand. This agrees quantitatively with the MO/DFT optimized geometry. Interpretation of free fitted CD values for As(V) binding suggests that the main surface species is a non-protonated bidentate complex (B) with a contribution of a singly protonated surface complex (MH) at sub-neutral pH and high loading. In addition, a protonated bidentate surface complex (BH) may be present. The same species are found if the theoretical CD values are used in the data analysis. The pH dependency of surface speciation is strongly influenced by the charge attribution of adsorbed species to the electrostatic surface plane while the effect of loading is primarily controlled by the amount of charge attributed to the 1-plane, illustrating the different action of the CD value. The MO/DFT geometry optimizations furthermore suggest that for As(V) the B, MH and BH surface complexes may have very similar AsFe distances which may complicate the interpretation of EXAFS data.
Metal ion binding to iron oxides
Hiemstra, T. ; Riemsdijk, W.H. van; Benedetti, M.F. ; Ponthieu, M. - \ 2006
Geochimica et Cosmochimica Acta 70 (2006)11. - ISSN 0016-7037 - p. 2679 - 2698.
goethite alpha-feooh - intrinsic proton affinity - solid-solution interface - reactive surface groups - hydrous ferric-oxide - exafs spectroscopy - adsorption behavior - water interfaces - humic substances - pb(ii) sorption
The biogeochemistry of trace elements (TE) is largely dependent upon their interaction with heterogeneous ligands including metal oxides and hydrous oxides of iron. The modeling of TE interactions with iron oxides has been pursued using a variety of chemical models. The objective of this work is to show that it is possible to model the adsorption of protons and TE on a crystallized oxide (i.e., goethite) and on an amorphous oxide (HFO) in an identical way. Here, we use the CD-MUSIC approach in combination with valuable and reliable surface spectroscopy information about the nature of surface complexes of the TE. The other objective of this work is to obtain generic parameters to describe the binding of the following elements (Cd, Co, Cu, Ni, Pb, and Zn) onto both iron oxides for the CD-MUSIC approach. The results show that a consistent description of proton and metal ion binding is possible for goethite and HFO with the same set of model parameters. In general a good prediction of almost all the collected experimental data sets corresponding to metal ion binding to HFO is obtained. Moreover, dominant surface species are in agreement with the recently published surface complexes derived from X-ray absorption spectroscopy (XAS) data. Until more detailed information on the structure of the two iron oxides is available, the present option seems a reasonable approximation and can be used to describe complex geochemical systems. To improve our understanding and modeling of multi-component systems we need more data obtained at much lower metal ion to iron oxide ratios in order to be able to account eventually for sites that are not always characterized in spectroscopic studies.
Microscale and Pb distribution patterns in subsurface soil horizons: an indication for metal transport dynamics
Oort, F. van; Jongmans, A.G. ; Citeau, L. ; Chevallier, P. - \ 2006
European Journal of Soil Science 57 (2006)2. - ISSN 1351-0754 - p. 154 - 166.
smelter-contaminated soils - heavy-metals - exafs spectroscopy - pollution - land - lead - cd - microprobe - solubility - speciation
In many studies on soil pollution, authors conclude that there is no downward migration of metal elements if no evidence for enrichment can be inferred from profiles of total metal contents. We assessed possible transfer of mobile and less mobile metal pollutants to depth in subsurface horizons of a heavy metal contaminated soil, by a study of specific pedofeatures in thin sections by optical microscopy, and their corresponding Zn and Pb distribution patterns by synchrotron-based X-ray microfluorescence. In the B horizon (70 cm depth), Zn accumulation was predominantly associated with clay-iron coatings. Strong correlation was found between Zn and Fe (r = 0.94), Zn and Mn (r = 0.75), Zn and Ti (r = 0.84), and Zn and K (r = 0.88), but significant correlation was absent between Zn and Pb. In the C horizon (100 cm depth), clear Pb accumulation was observed in distinct iron coatings, with large correlation coefficients found between Pb and Fe (r = 0.94-0.75), whereas correlation between Zn and Fe was absent. Detected Zn concentrations were small and attributed to the local natural geochemical background. These results were then compared with data of the composition of gravitational soil water collected in other soils from the same study area. Thus, Zn accumulation in the B horizon was ascribed to interception of dissolved Zn2+ by negatively charged constituents of clay-iron coatings. In contrast, Pb accumulation in C horizons was related to precipitation of Pb-bearing iron colloids leading to neoformed, optically pure iron oxyhydroxide crystals and coatings. We demonstrate very localized accumulation of almost immobile Pb which occurs at greater depth than the more mobile Zn. The common, but strongly localized, occurrence of Pb-bearing iron coatings in the soil groundmass explained the absence of changes in the total Pb concentrations of the C horizon compared with the concentrations in the B horizon.
Analysis of copper binding in the ternary system Cu2+/Humic Acid/Goethite at neutral to acidic pH
Saito, T. ; Koopal, L.K. ; Nagasaki, S. ; Tanaka, S. - \ 2005
Environmental Science and Technology 39 (2005)13. - ISSN 0013-936X - p. 4886 - 4893.
metal-ion binding - adsorbed humic substances - natural organic-matter - competitive adsorption - exchange properties - charge adjustments - exafs spectroscopy - fulvic-acid - goethite - model
Binding of heavy metal and actinide ions to natural colloids, such as humic substances (HSs) and metal (hydr)oxides, plays an important role in the ecotoxicological behavior of these ions. Several thermodynamic models have been constructed to predict the speciation of these ions in metal/HS or metal/oxide binary systems. However, in natural environments the adsorption of HSs on oxides can influence the binding of target metals, leading to deviation from the additivity of calibrated binary models. In this study binding of copper (Cu 2+) to the purified Aldrich humic acid (PAHA)/goethite complex in the neutral to acidic pH region was investigated by measuring Cu2+ binding isotherms. The measured isotherms were compared with the results obtained for the binary systems under similar conditions. The comparison revealed that Cu2+ binding in the ternary system is enhanced with respect to the sum of Cu2+ binding in the corresponding binary systems. From the analysis of the charging behavior of the adsorbed PAHA as well as the smeared-out potential profile near the PAHA/goethite interface, the increase of Cu2+ binding to the complex was mainly attributed to the decrease of proton competition to the functional groups of the adsorbed PAHA and the change of the electrostatic potential in the vicinity of the goethite surface
Morphology, chemistry and distribution of neoformed spherulites in agricultural land affected by metallurgical point-source pollution
Leguedois, S. ; Oort, F. van; Jongmans, A.G. ; Chevalier, P. - \ 2004
Environmental Pollution 130 (2004)2. - ISSN 0269-7491 - p. 135 - 148.
smelter-contaminated soils - sequential extraction - exafs spectroscopy - speciation - lead - microprobe - france - metals - zn - pb
Metal distribution patterns in superficial soil horizons of agricultural land affected by metallurgical point-source pollution were studied using optical and electron microscopy, synchrotron radiation and spectroscopy analyses. The site is located in northern France, at the center of a former entry lane to a bunker of World War 11, temporarily paved with coarse industrial waste fragments and removed at the end of the war. Thin sections made from undisturbed soil samples from A and B horizons were studied. Optical microscopy revealed the occurrence of yellow micrometer-sizcd (Ap horizon) and red decamicroineter-sized spherulites (AB, B(1)g horizons) as well as distinct distribution patterns. The chemical composition of the spherulites was dominated by Fe, Mn, Zn, Pb, Ca, and P. Comparison of calculated Zn stocks, both in the groundmass and in spherulites, showed a quasi-exclusive Zn accumulation in these neoformed features. Their formation was related to several factors: (i) liberation of metal elements due to weathering of waste products, (ii) Ca and P supply from fertilizing practices, (iii) co-precipitation of metal elements and Ca and P in a Porous soil environment, after slow exudation of a supersaturated soil solution in more confined mineral media. (C) 2004 Elsevier Ltd. All rights reserved.
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