| 1. |
- Baken, Stijn, et al.
(författare)
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Characterisation of hydrous ferric oxides derived from iron-rich groundwaters and their contribution to the suspended sediment of streams
- 2013
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 39, s. 59-68
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Tidskriftsartikel (refereegranskat)abstract
- When Fe(II) bearing groundwaters surface in streams, particulate authigenic Fe-rich material is produced by oxidation. Such freshly precipitated Fe minerals may be transported as suspended sediment and have a profound impact on the fate of trace metals and nutrients in rivers. The objective of this study was to monitor changes in mineralogy and composition of authigenic material from its source to streams of increasing order. Groundwaters, surface waters, and suspended sediment in streams of different order were sampled in the Kleine Nete catchment (Belgium), a lowland with Fe-rich groundwaters (3.5-53.8 mg Fe/L; pH 6.3-6.9). Fresh authigenic material (>0.45 mu m) was produced by oxidising filtered (<0.45 mu m) groundwater and surface water. This material contained, on average, 44% Fe, and smaller concentrations of C, P, and Ca. Iron EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy showed that the Fe was present as poorly crystalline hydrous ferric oxides with a structure similar to that of ferrihydrite. The Fe concentration in the suspended sediment samples decreased to 36-40% (stream order 2), and further to 18-26% (stream order 4 and 5). Conversely, the concentrations of organic C, Ca, Si, and trace metals increased with increasing stream order, suggesting mixing of authigenic material with suspended sediment from a different source. The Fe speciation in the suspended sediment was similar to that in fresh authigenic material, but more Fe-Fe interactions were observed, i.e. it was increasingly hydrolysed, suggesting ageing reactions. The suspended sediment in the streams of order 4 and 5 is estimated to contain between 31% and 59% of authigenic material, but more data are needed to refine this estimate. The authigenic material is an important sink for P in these streams which may alleviate the eutrophication risk in this catchment.
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| 2. |
- Cornelis, Geert, et al.
(författare)
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Solubility and transport of Cr(III) in a historically contaminated soil – Evidence of a rapidly reacting dimeric Cr(III) organic matter complex
- 2017
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 189, s. 709-716
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Tidskriftsartikel (refereegranskat)abstract
- Chromium is a common soil contaminant and, although it has been studied widely, questions about its speciation and dissolutions kinetics remain unanswered. We combined information from an irrigation experiment performed with intact soil columns with data from batch experiments to evaluate solubility and mobilization mechanisms of Cr(III) in a historically contaminated soil (>65 years). Particulate and colloidal Cr(III) forms dominated transport in this soil, but their concentrations were independent of irrigation intensity (2-20 mm h(-1)). Extended X-ray absorption fine structure (EXAFS) measurements indicated that Cr(III) associated with colloids and particles, and with the solid phase, mainly existed as dimeric hydrolyzed Cr(III) bound to natural organic matter. Dissolution kinetics of this species were fast (<= 1 day) at low pH (<3) and slightly slower (<= 5 days) at neutral pH. Furthermore, it proved possible to describe the solubility of the dimeric Cr(III) organic matter complex with a geochemical equilibrium model using only generic binding parameters, opening the way for use of geochemical models in risk assessments of Cr(III)-contaminated sites. (C) 2017 The Authors. Published by Elsevier Ltd.
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| 3. |
- de Campos Pereira, Hugo, et al.
(författare)
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The Adsorption of Per- and Polyfluoroalkyl Substances (PFASs) onto Ferrihydrite Is Governed by Surface Charge
- 2020
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 54, s. 15722-15730
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Tidskriftsartikel (refereegranskat)abstract
- An improved quantitative and qualitative understanding of the interaction of per- and polyfluoroalkyl substances (PFASs) and short-range ordered Fe (hydr)oxides is crucial for environmental risk assessment in environments low in natural organic matter. Here, we present data on the pH-dependent sorption behavior of 12 PFASs onto ferrihydrite. The nature of the binding mechanisms was investigated by sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy and by phosphate competition experiments. Sulfur K-edge XANES spectroscopy showed that the sulfur atom of the head group of the sulfonated PFASs retained an oxidation state of +V after adsorption. Furthermore, the XANES spectra did not indicate any involvement of inner-sphere surface complexes in the sorption process. Adsorption was inversely related to pH (p < 0.05) for all PFASs (i.e., C-3-C-5 and C-7-C-9 perfluorocarboxylates, C-4, C-6, and C-8 perfluorosulfonates, perfluorooctane sulfonamide, and 6:2 and 8:2 fluorotelomer sulfonates). This was attributed to the pH-dependent charge of the ferrihydrite surface, as reflected in the decrease of surface zeta-potential with increasing pH. The importance of surface charge for PFAS adsorption was further corroborated by the observation that the adsorption of PFASs decreased upon phosphate adsorption in a way that was consistent with the decrease in ferrihydrite zeta-potential. The results show that ferrihydrite can be an important sorbent for PFASs with six or more perfluorinated carbons in acid environments (pH <= 5), particularly when phosphate and other competitors are present in relatively low concentrations.
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| 4. |
- Gustafsson, Jon Petter, 1964-, et al.
(författare)
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Chromium (III) and bismuth (III) complexation to organic matter : EXAFS Spectroscopy and equilibrium modeling
- 2013
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Ingår i: Mineralogical magazine. - 0026-461X .- 1471-8022. ; 77:5, s. 1235-
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Tidskriftsartikel (refereegranskat)abstract
- The complexation of chromium(III) and bismuth(III) to organic matter was investigated by batch equilibrations with Suwannee River Fulvic Acid (SRFA) and with mor layer material (Risbergshöjden Oe). In the SRFA systems, 3 mM chromium(III) solutions were equilibrated with 9 g L-1 SRFA and equilibrated at different pH values ranging from 2 to 6. Characterization of the reaction products was made at MAX-Lab, Lund, Sweden, using Cr K-edge EXAFS spectroscopy at 5 989 eV. The spectra were interpreted using both conventional data treatment using EXAFSPAK and with wavelet transform (WT) analysis. The results show that chromium(III) formed monomeric organic complexes with SRFA. There was no evidence of polymerization with the exception of the particulate phase at pH 6, which was attributed to a limited extent of Cr(OH)3 formation.The mor layer material was equilibrated with chromium(III) and bismuth(III) solutions as a function of pH, time and competing ions (iron(III), aluminium(III), copper(II)). Again CrK-edge and Bi L3-edge EXAFS spectroscopy was used, at 5 989 and 13 419 eV. The experiments showed a predominance of monomeric organic complexes for chromium(III). The sorption of chromium(III) was pH-dependent and to some extent found to be influenced by competition from aluminium(III) and copper(II). Chromium(III) complexation was found to be very slow at pH < 4, and equilibration times of three months or longer were required to reach equilibrium under these conditions. Concerning bismuth(III), complexation was quicker and found to be very strong, with more than 94 % bound at pH 1.2 at a high bismuth(III) loading. EXAFS spectroscopy showed that two complexes were involved, one monomeric and one di- or trimeric, with the latter being predominant at higher pH values, although it was present already at pH 1.2. In the organic bismuth(III) complexes, the bismuth(III) octahedron was found to be strongly distorted, which implies strong binding to organic acid functional groups. The complexation of bismuth(III) remained essentially unchanged even in the presence of a potent competitor such as iron(III).The results from the spectroscopic investigation and from the quantitative solution data were used to calibrate new and improved complexation models for the Stockholm Humic (SHM) and the NICA-Donnan models. In the case of the Stockholm Humic Model, both complexes as found by EXAFS spectroscopy were considered explicitly; this ensured the model to predict minimum competition effects in agreement with the laboratory results.
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| 5. |
- Gustafsson, Jon Petter, et al.
(författare)
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Chromium(III) complexation to natural organic matter : Mechanisms and modeling
- 2014
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 48:3, s. 1753-1761
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Tidskriftsartikel (refereegranskat)abstract
- Chromium is a common soil contaminant, and it often exists as chromium(III). However, limited information exists on the coordination chemistry and stability of chromium(III) complexes with natural organic matter (NOM). Here, the complexation of chromium(III) to mor layer material and to Suwannee River Fulvic Acid (SRFA) was investigated using EXAFS spectroscopy and batch experiments. The EXAFS results showed a predominance of monomeric chromium(III)-NOM complexes at low pH (<5), in which only Cr··C and Cr-O-C interactions were observed in the second coordination shell. At pH > 5 there were polynuclear chromium(III)-NOM complexes with Cr···Cr interactions at 2.98 Å and for SRFA also at 3.57 Å, indicating the presence of dimers (soil) and tetramers (SRFA). The complexation of chromium(III) to NOM was intermediate between that of iron(III) and aluminum(III). Chromium(III) complexation was slow at pH < 4: three months or longer were required to reach equilibrium. The results were used to constrain chromium-NOM complexation in the Stockholm Humic Model (SHM): a monomeric complex dominated at pH < 5, whereas a dimeric complex dominated at higher pH. The optimized constant for the monomeric chromium(III) complex was in between those of the iron(III) and aluminum(III) NOM complexes. Our study suggests that chromium(III)-NOM complexes are important for chromium speciation in many environments.
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| 6. |
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| 7. |
- Herting, Gunilla, et al.
(författare)
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Release of Si from Silicon, a Ferrosilicon (FeSi) Alloy and a Synthetic Silicate Mineral in Simulated Biological Media
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:9, s. e107668-
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Tidskriftsartikel (refereegranskat)abstract
- Unique quantitative bioaccessibility data has been generated, and the influence of surface/material and test media characteristics on the elemental release process were assessed for silicon containing materials in specific synthetic body fluids at certain time periods at a fixed loading. The metal release test protocol, elaborated by the KTH team, has previously been used for classification, ranking, and screening of different alloys and metals. Time resolved elemental release of Si, Fe and Al from particles, sized less than 50 mm, of two grades of metallurgical silicon (high purity silicon, SiHG, low purity silicon, SiLG), an alloy (ferrosilicon, FeSi) and a mineral (aluminium silicate, AlSi) has been investigated in synthetic body fluids of varying pH, composition and complexation capacity, simple models of for example dermal contact and digestion scenarios. Individual methods for analysis of released Si (as silicic acid, Si(OH)(4)) in synthetic body fluids using GF-AAS were developed for each fluid including optimisation of solution pH and graphite furnace parameters. The release of Si from the two metallurgical silicon grades was strongly dependent on both pH and media composition with the highest release in pH neutral media. No similar effect was observed for the FeSi alloy or the aluminium silicate mineral. Surface adsorption of phosphate and lactic acid were believed to hinder the release of Si whereas the presence of citric acid enhanced the release as a result of surface complexation. An increased presence of Al and Fe in the material (low purity metalloid, alloy or mineral) resulted in a reduced release of Si in pH neutral media. The release of Si was enhanced for all materials with Al at their outermost surface in acetic media.
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| 8. |
- Larsson, Maja, et al.
(författare)
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Vanadate complexation to ferrihydrite : X-ray absorption spectroscopy and CD-MUSIC modelling
- 2017
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Ingår i: Environmental Chemistry. - : CSIRO Publishing. - 1448-2517 .- 1449-8979. ; 14:3, s. 141-150
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Tidskriftsartikel (refereegranskat)abstract
- The mobility of vanadium in the environment is influenced by sorption to metal (hydr)oxides, especially those containing iron. The aim of this study is to understand the adsorption behaviour of vanadium on poorly ordered (two-line) ferrihydrite (Fh). A further objective was to determine the binding mechanism of vanadate(V) to ferrihydrite surfaces in aqueous suspension to constrain the CD-MUSIC surface complexation model. Vanadium adsorption to ferrihydrite was evaluated by batch experiments which included series with different Fh-to-V ratios and pH values. Vanadate(V) adsorption was also evaluated in the presence of phosphate to compete with vanadate(V) for the available surface sites on ferrihydrite. In agreement with earlier studies, vanadate(V) was strongly adsorbed to ferrihydrite and the adsorption increased with decreasing pH. In the presence of phosphate, less vanadate(V) was adsorbed. Analysis by X-ray absorption near-edge structure spectroscopy revealed that the adsorbed vanadium was tetrahedral vanadate(V), VO4, regardless of whether vanadate(V) or vanadyl(IV) was added to the system. Spectra collected by extended X-ray absorption fine structure spectroscopy showed that vanadate(V) is bound primarily as an edge-sharing bidentate complex with VFe distances around 2.8 angstrom. Based on this information, a surface complexation model was set up in which three bidentate vanadate(V) complexes with different degrees of protonation were included. The model provided a satisfactory description of vanadate(V) adsorption over most of the pH and concentration ranges studied, also in the presence of competing phosphate ions.
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| 9. |
- Löv, Åsa, et al.
(författare)
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Evaluating the ability of standardised leaching tests to predict metal(loid) leaching from intact soil columns using size-based elemental fractionation
- 2019
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 222, s. 453-460
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory-based leaching tests are frequently used for in situ risk assessments of contaminant leaching to groundwater and surface waters. This study evaluated the ability of three standardised leaching tests to assess leaching of lead (Pb), zinc (Zn), arsenic (As) and antimony (Sb) from four intact soil profiles, by considering particulate (0.45-8 mu m; percolation test), colloidal (10 kDa-0.45 mu m) and truly dissolved (<10 kDa) fractions of these elements. Deionised water was used as the percolation test leachant, while either deionised water or 1 mM CaCl2 was used in batch tests. Data from an irrigation experiment were used as reference. The results indicated that in percolation tests, leachate should be collected at a liquid:solid ratio (L/S) range of 2-10, instead of 0-0.5 or 0.5-2. Even at L/S = 2-10, the percolation test overestimated total Pb concentration, mainly because of greater mobilisation of particle-bound Pb, but appeared suitable for categorising soils into high/low risk with respect to mobilisation of particulate and colloidal contaminants. The batch test performed better with CaCl2 than with deionised water when standard membrane filtration (0.45 gm) was used, as the high Ca2+ concentration reduced colloidal mobilisation, avoiding overestimation of concentrations of elements such as Pb. However, the higher Ca2+ concentration and lower pH could result in overestimated concentrations of weakly sorbed elements, e.g. Zn. (C) 2019 The Authors. Published by Elsevier Ltd.
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| 10. |
- Löv, Åsa, et al.
(författare)
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Particle- and colloid-facilitated Pb transport in four historically contaminated soils - Speciation and effect of irrigation intensity
- 2018
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927. ; 96, s. 327-338
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Tidskriftsartikel (refereegranskat)abstract
- Due to the low solubility of lead (Pb) in many soils, colloidal and particulate transport may have large effects on Pb leaching. However, the role of colloidal and particulate transport varies considerably between soils and the mechanisms controlling mobilisation are complex and poorly known. Furthermore, increased frequency of high-intensity rainfall events is expected in some parts of Europe and North America in response to climate change, which might increase the mobilisation of particles and colloids. In this work, we investigated transport of particulate ( > 0.45 mu m), colloidal (10 kDa-0.45 mu m) and truly dissolved ( < 10 kDa) Pb in an irrigation experiment on intact soil columns from four historically contaminated soils. We also investigated the effect of irrigation intensity (2-20 mmh(-1)) on Pb leaching in these fractions. The mechanism binding Pb on particles and colloids was evaluated by extended X-ray absorption fine structure (EXAFS) spectroscopy and geochemical modelling. A 10-fold increase in irrigation intensity brought about at most a three-fold change in leached particulate and colloidal Pb concentrations. In contrast, the fraction of leached Pb associated with particles and colloids varied by one order of magnitude between soils. Hence, the results suggest that it is more important to consider soil type than potential future increases in rainfall. For one soil with high concentrations of both arsenic (As) and Pb, geochemical modelling indicated that mimetite, Pb-5(AsO4)(3)Cl(s), was the major Pb species in the colloidal and particulate fractions. For the other three soils, EXAFS of Pb on isolated particles and colloids indicated that ferrihydrite was a major phase-sorbing Pb and this was supported by geochemical equilibrium modelling. Thus geochemical modelling can be used to indicate the speciation of Pb in particles and colloids leached in intact soils.
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| 11. |
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| 12. |
- Sjöstedt, Carin, 1981-, et al.
(författare)
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A consistent equilibrium model for pH, and aluminum and iron speciation in Swedish lakes and streams
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Consistent models that account for true geochemical conditions are needed in order to be able to model e.g. aluminum speciation as a result of acid rain, and metal speciation at contaminated sites. However, most geochemical models that exist today are calibrated either to a certain element or a certain site. We present a consistent chemical equilibrium model for pH and speciation of aluminum and iron, which was validated on a large number of lakes and rivers from various environments all over Sweden (n=3400). The model was based on the Visual Minteq program version 2.61, and used the Stockholm Humic Model for organic complexation. The only parameters that were calibrated were the Fe(III) binding constants to DOM and the fraction of active dissolved organic matter. These were later kept constant throughout the study to test the generality of the model. Results gave an error in pH prediction of less than 0.2 pH units in average, and inorganic monomeric aluminum of less than 1.5 µmol L-1. Particulates of Al and Fe(III) were also reasonably well modeled as hydroxides at pH-values above 5.5 when compared to a dataset of 0.45 µm filtered water. The model can be used for prediction of Al toxicity for fish, but also be used to simulate changes in Al speciation due to changes in dissolved organic carbon concentrations and sulfate concentrations in surface waters.
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| 13. |
- Sjöstedt, Carin, et al.
(författare)
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Complexation of Arsenite, Arsenate, and Monothioarsenate with Oxygen-Containing Functional Groups of Natural Organic Matter: An XAS Study
- 2019
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 53, s. 10723-10731
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Tidskriftsartikel (refereegranskat)abstract
- Arsenic (As) is reported to be effectively sorbed onto natural organic matter (NOM) via thiol coordination and polyvalent metal cation bridged ternary complexation. However, the extent of sorption via complex-ation with oxygen-containing functional groups of NOM is poorly understood. By equilibrating arsenite, arsenate, and monothioarsenate with purified model-peat, followed by As K-edge X-ray absorption spectroscopic analysis, this study shows that complexation with oxygen-containing functional groups can be an additional or alternative mode of As sorption to NOM. The extent of complexation was highest for arsenite, followed by monothioarsenate and arsenate. Complexation was higher at pH 7.0 compared to 4.5 for arsenite and arsenate and vice versa for monothioarsenate because of partial transformation to arsenite at pH 4.5. Modeling of the As K-edge extended X-ray absorption fine structure data revealed that As center dot center dot center dot C interatomic distances were relatively longer in arsenate- (2.83 +/- 0.01 angstrom) and monothioarsenate-treated peat (2.80 +/- 0.02 angstrom) compared to arsenite treatments (2.73 +/- 0.01 angstrom). This study suggests that arsenite was predominantly complexed with carboxylic groups, whereas arsenate and monothioarsenate were complexed with alcoholic groups of the peat. This study further implies that in systems, where NOM is the major sorbent, arsenate and monothioarsenate can have higher mobility than arsenite.
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| 14. |
- Sjöstedt, Carin, et al.
(författare)
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Evidence of the mineral ZnHAsO4 center dot H2O, koritnigite, controlling As(V) and Zn(II) solubility in a multi-contaminated soil
- 2022
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927. ; 140
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Tidskriftsartikel (refereegranskat)abstract
- Assessing element speciation and solubility control mechanisms in multi-contaminated soils poses great challenges. In this study, we examined the speciation and mechanisms controlling the solubility of As and Zn in a soil historically contaminated with As, Cu, Cr, and Zn salts used for wood preservation. The leaching behavior of dissolved species, particles, and colloids was studied in an irrigation experiment with intact soil columns. Batch experiments were used to study the solubility of dissolved species as a function of pH (2-8). The speciation of As and Zn in bulk soil and leached particles was studied with microscale X-ray fluorescence (mu-XRF) and extended Xray absorption fine structure (EXAFS) spectroscopy. Chemical speciation and solubility were evaluated by geochemical modelling. mu-XRF of bulk soil and particles showed that As and Zn were correlated in space. Bulkand mu-EXAFS of As and Zn, in combination with calculated ion activity products of possible As-Zn minerals, suggested a koritnigite (ZnHAsO4 center dot H2O) phase controlling the dissolved fraction of As(V) and Zn with an apparent log K-sp of 21.9 +/- 0.46. This phase lowered the solubility of As by almost two orders of magnitude in soil at pH > 5, and could therefore be of great importance at other multi-contaminated sites.
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| 15. |
- Sjöstedt, Carin, et al.
(författare)
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Fate of silicon in tropical agricultural soil clays using XANES spectroscopy
- 2023
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Ingår i: Applied Clay Science. - 0169-1317. ; 245
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Tidskriftsartikel (refereegranskat)abstract
- Silicon (Si) is an abundant element in terrestrial ecosystems and makes essential contributions to agricultural crops, environments, and industries; however, current knowledge of Si speciation in soil systems is based primarily on crystalline mineral types with limited information about the effect of Si-adsorbed species on the most chemically reactive clay fraction. Herein, we investigated Si speciation in the clay-sized fraction of tropical soils. Silicon K-edge X-ray absorption near edge structure (XANES) spectra of clay samples, together with a wide range of reference compounds varying in clay and Fe/Al oxide mineralogy, showed the predominance of Si in a beidellite structure and of Si adsorbed to montmorillonite and to kaolinite. Unique features, including a pre-whiteline feature, white-line position and intensity, and post-edge numbers and positions of Si reference spectra, could differentiate most Si reference standard spectra. Silicon adsorbed to goethite, Si-ferrihydrite-natural organic matter complexes, and Si in the structure of biotite, illite-smectite, chlorite, quartz, and Si nanoparticle, variously occurred in different samples. The CaCl2 extraction data revealed that extracted Si was below the limits of Si deficiency in one-half of the total soil samples and accounted for only 0.02% of total soil Si. Soil extractable Si had a positive correlation with pH, organic matter, and clay. Our results present a novel application of Si K-edge XANES as a tool for identifying Si speciation in natural clays that are the most chemically reactive phase of Si retention and release in terrestrial and aquatic systems.
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| 16. |
- Sjöstedt, Carin, et al.
(författare)
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Improved geochemical modeling of lead solubility in contaminated soils by considering colloidal fractions and solid phase EXAFS speciation
- 2018
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927. ; 92, s. 110-120
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Tidskriftsartikel (refereegranskat)abstract
- Lead (Pb) is a common contaminant in soils at e.g. mining, shooting range, and glassworks sites. In order to make reliable risk assessments and appropriate decisions on various "gentle remediation options", such as applying phosphate, compost, or zero-valent iron to soils, the binding mechanism of Pb and its speciation needs to be known. Multi-surface geochemical equilibrium models are useful tools for estimating trace metal solubility and speciation, but for Pb the predictions are often poor. This study evaluates the recent parameterization for Pb in the Visual MINTEQ code for its ability to predict the solubility of Pb at different pH values in four historically contaminated Swedish soils. As an independent validation of the model performance, the modeled solid-phase speciation was compared to measured Pb speciation retrieved using extended X-ray absorption fine structure (EXAFS) spectroscopy. Furthermore, potential artefacts by the presence of Pb colloids were investigated by filtering solutions through both 0.45 pm and 10 kDa fillers. The model accuracy for predicting Pb solubility was improved compared with previous studies producing log root mean square error (RMSE) values below 0.42 in three out of four soils, just by using generic assumptions. The use of ultrafiltered (< 10 kDa) instead of the 0.45 mu m-filtered Pb concentrations lowered the RMSE with similar to 0.4 log units in two soils, giving a more accurate evaluation of the model performance. EXAFS proved to be a useful tool for validating and constraining the model, since the solid phase speciation did not exactly agree with the modeled results using default assumptions. However, a sample-specific optimization of the amount of "active" solid organic matter and Al + Fe hydroxides resulted in improved prediction of Pb solubility as well as better agreement with the EXAFS measurements. Solubility of Pb in the fourth, As-rich soil was probably controlled by Pb-5 (AsO4)(3)Cl (mimetite) with a solubility product constant of 10(-83.5)(3).
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| 17. |
- Sjöstedt, Carin, 1981-, et al.
(författare)
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Iron and aluminium phases in softwater lakes : identity and significance for copper binding
- 2009
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Aluminium and iron have been found to compete with copper for binding sites to dissolved organic matter (DOM) in soil systems and when using geochemical modelling. However, the knowledge of the phases of Al, Fe and DOM in natural waters is uncertain. The aim of this ongoing work is to advance the knowledge on the geochemistry of iron and aluminium so that the speciation of copper in lake water can be more accurately assessed. Water samples from three softwater lakes in Tyresta (Stockholm) (Fig. 1),Sweden, are filtered using 0.45 µm and using 1 kDa cross-flow ultrafiltration. The particles on the filters and the colloidal phases of iron are investigated by extended X-ray absorption fine structure (EXAFS) spectroscopy. Aluminium phases are investigated by Fourier transform infrared (FTIR) spectroscopy. Field-flow fractionation (FFF) is used to study the colloidal composition of iron, aluminium and DOM. The competition of Al and Fe with Cu on binding to DOM is explored with Cu titrations using an ion selective electrode. The results will be used to improve geochemical modelling. Preliminary results from EXAFS spectroscopy for an acid lake rich in DOM (Lake Trehörningen; pH 4.8, DOC = 22 mg/l) indicate that Fe is not present as a mineral in the colloids, instead it is bound as monomeric Fe(III) complexes to organic matter, which means that it probably competes with Cu for binding sites on DOM. Additional results will be presented at the conference.
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| 18. |
- Sjöstedt, Carin, 1981-
(författare)
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Iron and aluminium speciation in Swedish freshwaters : Implications for geochemical modelling
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Speciation governs transport and toxicity of trace metals and is important to monitor in natural waters. Geochemical models that predict speciation are valuable tools for monitoring. They can be used for risk assessments and future scenarios such as termination of liming. However, there are often large uncertainties concerning the speciation of iron and aluminium in the models, due to the complicated chemistry of these metals. Both are important in governing the speciation of other metals, due to (i) their capacity to form minerals onto which metals can adsorb and (ii) their ability to compete for binding sites to natural organic matter (NOM). Aluminium is also potentially toxic and is therefore closely monitored in acidified freshwaters. In this study different phases of iron in Swedish lakes were characterised. This required a good method for preconcentrating the iron colloids. A new method was developed in this thesis that uses an anion-exchange column to isolate the iron colloids prior to characterisation with extended X-ray absorption fine structure (EXAFS) spectroscopy. Iron was present as ferrihydrite in particles but was also strongly monomerically complexed to NOM in two Swedish lakes. Based on the results an internally consistent process-based geochemical equilibrium model was presented for Swedish freshwaters. The model was validated for pH (n = 9 400) and inorganic monomeric aluminium (Ali) (n = 3 400). The model could simulate pH and Ali simultaneously, and be used for scenario modelling. In this thesis, modelling scenarios for decreases and complete termination of liming are presented for the 3 000 limed Swedish lakes. The results suggest that liming can be terminated in 30 % of the Swedish lakes and decreased in many other lakes.
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| 19. |
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| 20. |
- Sjöstedt, Carin, 1981-, et al.
(författare)
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Iron speciation in soft-water lakes and soils as determined by EXAFS spectroscopy and geochemical modelling
- 2013
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533 .- 0046-564X. ; 105, s. 172-186
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Tidskriftsartikel (refereegranskat)abstract
- Complexation of iron by organic matter can potentially compete with toxic metals for binding sites. Iron(III) forms both monomeric and di/trimeric complexes with fulvic and humic acids, but the nature and extent of complexation with natural organic matter samples from soft-water lakes has not been extensively studied. The aim of this study was to determine the coordination of iron in complexes with organic matter in two soft-water lakes and in the surrounding Oe soil horizons. Iron K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy was performed on particles and large colloids (>0.45. μm) collected by in-line pre-filtration, and on smaller colloids isolated both on an AGMP-1 anion-exchange column and by concentration using 1000. Da ultrafiltration. The results showed that iron(III) was mainly present in monomeric complexes with organic matter, both in the lake water smaller colloids and in the soil samples. Evidence for iron(III) (hydr)oxides was found for the lake particles, in the ultrafiltration retentates, and in some of the soils. Overall, the results suggest that complexation of iron(III) to organic matter prevents hydrolysis into polymeric forms. Strong complexation of iron(III) would lead to competition with other metals for organic-matter binding sites.
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| 21. |
- Sjöstedt, Carin, 1981-, et al.
(författare)
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Lead and Copper Speciation in Swedish Lakes and Rivers : Iron and Organic Matter as Potential Particulate/Colloidal Carriers
- 2011
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Ingår i: 11th International Conference on the Biogeochemistry of Trace elements.
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Konferensbidrag (refereegranskat)abstract
- It is important to monitor the speciation of the potentially toxic metals lead and copper in surface waters. The speciation can be influenced by factors such as adsorption to iron (hydr)oxides and complexation to organic matter. The aim of this study is to explore the speciation of lead and copper in soft-water lakes and rivers in boreal forests, and investigate what kind of potential factors govern the speciation. Methods included 0.45 µm in-line pre-filtration, 1 kDa tangential flow ultrafiltration and geochemical modelling using the Visual MINTEQ program in two boreal lakes, compared with measured and modelled values of 0.45 syringe pre-filtered metals concentrations performed in Swedish lakes and rivers in a larger dataset. Preliminary results indicate that particulate iron can adsorb Pb. On the contrary, Cu in particulate form did not usually appear together with iron particles. Instead, copper was present more in the smaller size fractions and was possibly associated with organic matter.
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| 22. |
- Sjöstedt, Carin, 1981-, et al.
(författare)
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Modelling of pH and inorganic aluminium after termination of liming in 3 000 Swedish lakes
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Significant resources are spent on counteracting the effects of acidification, mainly by liming. Due to a lower sulphur and nitrogen deposition in Europe and North America, authorities are reducing liming, changing directives and strategies for remediation. However, as the acid-base buffer capacity differs in different water bodies, the desirable reduction of the lime dose is variable. In this study, a geochemical model is used to predict pH and inorganic monomeric aluminium (Ali) when liming reduced and finally terminated in the 3 000 Swedish lakes that have been subject to liming. The model used estimations of Ca and Mg concentrations not affected by liming based upon the Ca/Mg ratio in nearby unlimed reference lakes. For modelling of pH and inorganic aluminium we used the geochemical model program Visual MINTEQ including the Stockholm Humic Model recently calibrated for Swedish fresh water. The predictions were confirmed by results from six monitored lakes, in which liming had been terminated. The use of geochemical modelling proved to be a promising tool for the calculation of accurate lime requirements in acid waters. For simulations in which liming was completely terminated, the pH value decreased with, on average, 0.9 pH units to pH 5.9, whereas Ali increased with 18 μg L-1 to 31 μg L-1. If liming was reduced by half, the pH would drop only 0.3 pH units and Aliwould increase with 2 μg L-1. Lakes in the south-western part of Sweden were predicted to reach a lower pH and higher Ali, as could be expected due to their larger historical S deposition. The results indicate that liming can be terminated in certain areas and be reduced without large pH reductions in the fresh water.
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| 23. |
- Sjöstedt, Carin, et al.
(författare)
-
Modelling of pH and inorganic aluminium after termination of liming in 3000 Swedish lakes
- 2013
-
Ingår i: Applied Geochemistry. - : Elsevier. - 0883-2927 .- 1872-9134. ; 35, s. 221-229
-
Tidskriftsartikel (refereegranskat)abstract
- Significant resources are spent on counteracting the effects of acidification, mainly by liming. Due to lower S and N deposition in Europe and North America, authorities are changing directives and strategies for remediation and reducing liming. However, as the acid-base buffer capacity differs in different water bodies, the desirable reduction of the lime dose is variable. In this study, a geochemical model is used to predict pH and inorganic monomeric Al (Ali) when liming is reduced and finally terminated in the 3000 Swedish lakes currently treated with lime. To estimate Ca and Mg concentrations not affected by liming for use in the model, the Ca/Mg ratio in nearby unlimed reference lakes was used. For the modelling of pH and inorganic Al the Visual MINTEQ program including the Stockholm Humic Model recently calibrated for Swedish fresh water was used. The predictions were validated with modelling results from six monitored lakes, in which liming had been terminated. The use of geochemical modelling appeared to be a promising tool for the calculation of accurate lime requirements in acid waters. For simulations in which liming was completely terminated, the pH value decreased by, on average, 1 pH unit to pH 5.7, whereas Ali increased by 17 mu g L (1) to 32 mu g L (1). If liming was reduced by half, the pH would drop only 0.3 pH units and Ali would increase by 2 mu g L (1). Lakes in the south-western part of Sweden were predicted to reach a lower pH and higher Ali, which would be expected due to their greater historical S deposition. The results indicate that liming can be terminated in certain areas and in other areas be reduced without increases in the lake acidity.
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| 24. |
- Sjöstedt, Carin, 1981-, et al.
(författare)
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Målsjöinventeringen 07/08 - modellering av Ali och pH vid förändrad kalkning
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Målet med denna studie är att undersöka vad som händer vid en förändrad kalkning i sjöar, för att se om det går att minska på kalkdosen utan att det innebär en risk för låga pH och höga Ali-halter (monomert oorganiskt aluminium). De viktiga parametrarna pH och Ali har simulerats med en geokemisk jämviktsmodell, dels vid nuvarande uppmätta förhållanden i Målsjöinventeringen 07/08 (ca 3000 sjöar) och dels vid olika scenarier där kalcium- och magnesiumhalterna har minskat. Kalcium- och magnesiumkoncentrationerna har minskats ner till framräknade halter som är en uppskattning av vad de skulle vara i sjöarna utan tillsatt kalk, baserat på kvoten Ca*/Mg* i närliggande okalkade sjöar. För den ursprungliga situationen vid uppmätta förhållanden så hade mindre än 1% av de kalkade sjöarna över 30 μg L-1beräknad halt Ali och uppmätt pH låg på i medeltal 6,8. När istället icke-kalkpåverkade kalcium- och magnesiumkoncentrationer matades in i modellen, blev resultatet att pH minskade till i medeltal 5,7 och Ali ökade till i medeltal 31 μg L-1. Ca 40% av sjöarna fick pH-värden under 5,6 och ca 35% fick Ali-värden över 30 μg L-1. De faktorer som mest styrde vilka sjöar som fick lägst pH var dels hur mycket Ca och Mg-koncentrationerna minskade i förhållande till syraneutraliserande förmåga (ANC) (dvs mängden katjoner till starka baser minus anjoner till starka syror) och dels en geografisk skillnad. Om Ca- och Mg-koncentrationerna minskade med mer än 50% av ANC så minskade pH med mer än 0,4 pH-enheter. Det är alltså en riskfaktor som bör studeras innan avslutad eller minskad kalkning. De län som var mest drabbade av både surt pH och höga Ali-halter var Skånes, Hallands, Västra Götalands, Kronobergs och Örebros län. Där bör följaktligen kalkningen absolut fortsätta. Några län minskade dock väldigt lite i pH och ökade lite i Ali, speciellt Gävleborg och Jämtlands län. I dessa län bör man kunna överväga att minska ner på kalkningen. Om istället kalcium- och magnesiumkoncentrationerna bara minskades motsvarande en halverad kalkning skedde en mycket mindre förändring av pH och Ali. Antalet sjöar med pH under 5,6 blev nu istället 2,5% och 3% hade Ali över 30 μg L-1. Det skulle kunna betyda att för de flesta sjöarna så skulle det gå att minska på kalkningen utan några dramatiska följder. Av sjöarna i denna studie så var de län som var mest drabbade Kronobergs, Örebros och Västra Götalands län, som därmed inte bör minska ner på kalkningen.
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| 25. |
- Sjöstedt, Carin S., et al.
(författare)
-
Chemical Equilibrium Modeling of Organic Acids, pH, Aluminum, and Iron in Swedish Surface Waters
- 2010
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 44:22, s. 8587-8593
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Tidskriftsartikel (refereegranskat)abstract
- A consistent chemical equilibrium model that calculates pH from charge balance constraints and aluminum and iron speciation in the presence of natural organic matter is presented. The model requires input data for total aluminum, iron, organic carbon, fluoride, sulfate, and charge balance ANC. The model is calibrated to pH measurements (n = 322) by adjusting the fraction of active organic matter only, which results in an error of pH prediction on average below 0.2 pH units. The small systematic discrepancy between the analytical results for the monomeric aluminum fractionation and the model results is corrected for separately for two different fractionation techniques (n = 499) and validated on a large number In = 3419) of geographically widely spread samples all over Sweden. The resulting average error for inorganic monomeric aluminum is around 1 mu M. In its present form the model is the first internally consistent modeling approach for Sweden and may now be used as a tool for environmental quality management Soil gibbsite with a log *K-s of 8.29 at 25 degrees C together with a pH dependent loading function that uses molar Al/C ratios describes the amount of aluminum in solution in the presence of organic matter if the pH is roughly above 6.0.
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| 26. |
- Sjöstedt, Carin, et al.
(författare)
-
Speciation of aluminium, arsenic and molybdenum in excessively limed lakes
- 2009
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 407:18, s. 5119-5127
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Tidskriftsartikel (refereegranskat)abstract
- The possible existence of the potentially toxic oxyanions of Al (AI(OH)(4)(-)). As (HAsO42-), and Mo (MoO42-) was examined in excessively limed lakes. In-situ dialysis (MWCO 1 kDa) was performed in the surface and bottom waters of two excessively limed lakes (pH 7.1-7.7) and one acidic lake (pH similar to 5.4). The dialysable metal concentrations were compared to the equilibrium distribution of species as calculated with the geochemical code Visual MINTEQ incorporating the CD-MUSIC and Stockholm Humic models for complexation onto colloidal ferrihydrite and dissolved organic matter. Arsenic and molybdenum in the excessively limed lakes were to a large extent present in the dialysable fraction (>79% and >92% respectively). They were calculated to exist as free or adsorbed oxyanions. Most of the Al was observed to reside in the colloidal fraction (51-82%). In agreement with this, model predictions indicated aluminium to be present mostly as colloids or bound to dissolved organic matter. Only a small fraction was modelled as AI(OH)(4)(-) ions. In most cases, modelled values were in agreement with the dialysis results. The free concentrations of the three oxyanions were mostly low compared to toxic levels.
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| 27. |
- Suresh, Prashanth, et al.
(författare)
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Arsenic adsorption by iron-aluminium hydroxide coated onto macroporous supports : Insights from X-ray absorption spectroscopy and comparison with granular ferric hydroxides
- 2016
-
Ingår i: Journal of Hazardous Materials. - : Elsevier. - 0304-3894 .- 1873-3336. ; 302, s. 166-174
-
Tidskriftsartikel (refereegranskat)abstract
- This paper evaluates the arsenic adsorption characteristics of a macroporous polymer coated with coprecipitated iron-aluminium hydroxides (MHCMP). The MHCMP adsorbent-composite fits best with a pseudo-second order model for As(III) and a pseudo-first order kinetic model for As(V). The MHCMP shows a maximum adsorption capacity of 82.3 and 49.6 mgAs/g adsorbent for As(III) and As(V) ions respectively, and adsorption followed the Langmuir model. Extended X-ray absorption fine structure showed that binding of As(III) ions were confirmed to take place on the iron hydroxides coated on the MHCMP, whereas for As(V) ions the binding specificity could not be attributed to one particular metal hydroxide. As(III) formed a bidentate mononuclear complex with Fe sites, whereas As(V) indicated on a bidentate binuclear complex with Al sites or monodentate with Fe sites on the adsorbent. The column experiments were run in a well water spiked with a low concentration of As(III) (100 mu g/L) and a commercially available adsorbent (GEH (R) 102) based on granular iron-hydroxide was used for comparison. It was found that the MHCMP was able to treat 7 times more volume of well water as compared to GEH (R) 102, maintaining the threshold concentration of less than 10 mu gAs/L, indicating that the MHCMP is a superior adsorbent.
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| 28. |
- Tiberg, Charlotta, et al.
(författare)
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Metal sorption to Spodosol Bs horizons : Organic matter complexes predominate
- 2018
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Ingår i: Chemosphere. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0045-6535 .- 1879-1298. ; 196, s. 556-565
-
Tidskriftsartikel (refereegranskat)abstract
- While metal sorption mechanisms have been studied extensively for soil surface horizons, little information exists for subsoils, for example Spodosol Bs horizons. Here the sorption of cadmium(10, copper(II) and lead(II) to seven Bs horizons from five sites was studied. Extended X-ray absorption fine structure (EXAFS) spectroscopy showed that cadmium(II) and lead(II) were bound as inner-sphere complexes to organic matter. Addition of o-phosphate (to 1 mu mol l(-1)) did not result in any significant enhancement of metal sorption, nor did it influence EXAFS speciation. An assemblage model using the SHM and CD-MUSIC models overestimated metal sorption for six out of seven soil samples. To agree with experimental results, substantial decreases (up to 8-fold) had to be made for the fraction 'active organic matter', f(Hs), while the point-of-zero charge (PZC) of ferrihydrite had to be increased. The largest decreases of f(HS) were found for the soils with the lowest ratio of pyrophosphate-to oxalate-extractable Al (Al-pyp/Al-ox), suggesting that in these soils, humic and fulvic acids were to a large extent inaccessible for metal sorption. The low reactivity of ferrihydrite towards lead(II) can be explained by potential spillover effects from co-existing allophane, but other factors such as ferrihydrite crystallisation could not be ruled out. In conclusion, organic matter was the predominant sorbent for cadmium(II), copper(II) and lead(II). However, for lead(II) the optimised model suggests additional, but minor, contributions from Fe (hydr) oxide surface complexes. These results will be important to correctly model metal sorption in spodic materials.
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| 29. |
- Tiberg, Charlotta, et al.
(författare)
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Phosphate competition with arsenate on poorly crystalline iron and aluminum (hydr)oxide mixtures
- 2020
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 255
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Tidskriftsartikel (refereegranskat)abstract
- Phosphate competes with arsenate for sorption sites on poorly crystalline iron and aluminum (hydr) oxides. The competition has implications e.g. for the management of arsenic-contaminated soil and water. Phosphate competition with arsenate on mixed phases containing both iron and aluminum (hydr) oxides has rarely been investigated. Here, the phosphate competition with arsenate on mixtures of poorly crystalline aluminum hydroxide (Alhox) and ferrihydrite (Fh), was investigated in batch experiments at pH 6.5. X-ray absorption spectroscopy (XAS) was performed on the phosphorus and arsenic K edges, which offered a unique insight in the partitioning of arsenate and phosphate on mixed Alhox-Fh sorbents. Under the studied conditions the sorption capacity of the mixed sorbents (per mol Al or Fe) increased at higher Alhox to Fh ratios. The XAS measurements provided direct evidence that phosphate competed more effectively with arsenate for sorption sites on Alhox than on Fh. For example, in a mixture with 50% of both sorbents and with similar additions of arsenate and phosphate, 71% of the oxyanions adsorbed on Fh and 46% on Alhox were arsenate. Consequently, phosphate may mobilize arsenate more easily from mixed iron-aluminum matrices that are rich in aluminum. (C) 2020 The Authors. Published by Elsevier Ltd.
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| 30. |
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| 31. |
- Tiberg, Charlotta, 1973-, et al.
(författare)
-
Phosphate effects on copper and lead sorption to iron oxide
- 2013
-
Ingår i: ICOBTE 2013. - Athens, Georgia.
-
Konferensbidrag (refereegranskat)abstract
- Elevated concentrations of phosphate affects the mobility of copper and lead in soil. More detailed knowledge about the mechanisms behind this is of interest for example in risk assessments of contaminated soils. It is well known that the mineral pyromorphite is formed at high concentrations of lead(II) and phosphate in combination with high pH. This effect has been used to immobilize metals in remediation of contaminated soil.Sorption mechanisms, on the other hand, act also at low concentrations of metal and phosphate when no precipitates are formed. It has been shown that the sorption of lead(II) to iron oxide surfaces can be enhanced in precence of phosphate. Exactly how phosphate interacts with lead(II) and iron oxide has not yet been established, and there are seemingly contradictory results. Phosphate effects on copper(II) sorption to iron oxy(hydro)xides has been less studied.Here, batch experiments, X-ray absorption spectroscopy (EXAFS) and surface complexation modeling with the three-plane CD-MUSIC model has been used to study the effect of phosphate on sorption of copper(II) and lead(II) to ferrihydrite. The aim is to investigate what surface complexes are formed and to derive new and improved surface complexation constants for adsorption to ferrihydrite.A similar approach including batch experiments, X-ray absorption spectroscopy (EXAFS) and modelling is now applied to investigate sorption to samples of Swedish forest soils.Results show that addition of phosphate increases the sorption of copper(II) and lead(II) to ferrihydrite in batch experiments. The EXAFS results show, in agreement with earlier studies, that copper(II) and lead(II) form bidentate mononuclear complexes on ferrihydrite in systems without phosphate. However, in the presence of phosphate, there are indications of ternary complexes. The results are being used to suggest new surface complexation constants for the reactions.Results from experiments with Swedish forest soils are currently being evaluated.
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| 32. |
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| 33. |
- Tiberg, Charlotta, et al.
(författare)
-
Phosphate effects on copper(II) and lead(II) sorption to ferrihydrite
- 2013
-
Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier. - 0016-7037 .- 1872-9533 .- 0046-564X. ; 120, s. 140-157
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Tidskriftsartikel (refereegranskat)abstract
- Transport of lead(II) and copper(II) ions in soil is affected by the soil phosphorus status. Part of the explanation may be that phosphate increases the adsorption of copper(II) and lead(II) to iron (hydr)oxides in soil, but the details of these interactions are poorly known. Knowledge about such mechanisms is important, for example, in risk assessments of contaminated sites and development of remediation methods. We used a combination of batch experiments, extended X-ray absorption fine structure (EXAFS) spectroscopy and surface complexation modeling with the three-plane CD-MUSIC model to study the effect of phosphate on sorption of copper(II) and lead(II) to ferrihydrite. The aim was to identify the surface complexes formed and to derive constants for the surface complexation reactions. In the batch experiments phosphate greatly enhanced the adsorption of copper(II) and lead(II) to ferrihydrite at pH < 6. The largest effects were seen for lead(II). Based on interpretation of the EXAFS spectra edge-sharing bidentate copper(II) or lead(II) complexes predominated in the single-sorbate systems with ferrihydrite. Lead(II) EXAFS spectra suggested a distinct change of coordination in the presence of phosphate, i.e. the signal from edge-sharing complexes diminished and a longer Pb center dot center dot center dot Fe distance appeared at about 4 angstrom. A similar, but less pronounced, pattern was observed for copper(II). Based on the results from interpretation of EXAFS spectra and surface complexation modeling with the CD-MUSIC model the enhanced sorption in presence of phosphate was most satisfactorily explained by the appearance of ternary metal-phosphate complexes in which the metal interacts directly with the surface. In conclusion, geochemical models used for simulating trace element behavior in acidic environments seem to require ternary metal-phosphate surface complexes to properly describe partitioning of metals between solution and the solid phase.
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| 34. |
- Tiberg, Charlotta, et al.
(författare)
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Speciation of Cu and Zn in bottom ash from solid waste incineration studied by XAS, XRD, and geochemical modelling
- 2021
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 119, s. 389-398
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Tidskriftsartikel (refereegranskat)abstract
- Millions of tons of bottom ash (BA) is generated from incineration of industrial and municipal solid waste each year within EU. The magnitude of leaching of metals like Cu and Zn is critical for hazard and risk assessment of these ashes. Although speciation of metals is a key factor to understand and predict metal leaching, speciation of Cu and Zn in BA is not well known. In this study six metal separated and carbonized BA were investigated by a combination of X-ray absorption spectroscopy, X-ray diffraction, leaching/extraction tests, and geochemical modelling. Five of the BA were from grate boilers and one from a fluidized bed incinerator. The aims were to identify similarities in Cu and Zn speciation and to identify main species. The combination of several techniques was necessary to draw conclusions about speciation and displayed coherent results. A similar speciation of Cu and Zn was indicated in the five studied grate boiler ashes although the proportions between species may vary. Copper(II) oxide and Cu metal were the main Cu species in all BA. Zinc(II) oxide and willemite (Zn2SiO4) were identified in grate boiler ashes. The fluidized bed ash contained Zn-Si-minerals and possibly franklinite or gahnite, while the Zn(II) oxide content was low, if any. The results have implications for classification and risk assessment of MIBA.
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