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  • 1. Berger, T.
    et al.
    Mathurin, F. A.
    Gustafsson, Jon Petter
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. Swedish University of Agricultural Sciences, Sweden.
    Peltola, P.
    Åström, M.E.
    The impact of fluoride on Al abundance and speciation in boreal streams2015Inngår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 409, s. 118-124Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The impact of fluoride on the abundance and speciation of aluminium (Al) was investigated in three boreal streams characterised by overall high concentrations of fluoride and dissolved organic matter. Stream-water sampling was carried out several times a year for at least 4 years, and a chemical equilibrium model (Visual MINTEQ) was applied in order to model the proportion of colloidal and organically/inorganically complexed Al in the waters. The Al concentrations in filtered (0.45 μm) water samples were inversely correlated with pH, and reached values up to approximately 1. mg/L during low pH conditions (pH < 6.0). In a stream with high fluoride concentrations, as compared to a similar stream with only moderately elevated fluoride concentrations, the Al concentrations were consistently elevated. For the stream with high concentrations of fluoride and Al, the model predicted both high concentrations and proportions of Al-fluoride complexation. This prediction indicates that high fluoride levels contribute to raise both the Al abundance and the ratio of inorganic to organic Al complexation in stream water. In contrast, for another stream with high fluoride concentrations and consistently high (near neutral) pH, there was no evidence of fluoride affecting Al concentration or complexation. These results show that it is important to focus future studies on the role of high levels of dissolved fluoride on both the speciation and the toxicity of Al in stream water.

  • 2.
    Biswas, Ashis
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik. University of Kalyani, India .
    Neidhardt, Harald
    Kundu, Amit K.
    Halder, Dipti
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik. University of Kalyani, India .
    Chatterjee, Debashis
    Berner, Zsolt
    Jacks, Gunnar
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik.
    Bhattacharya, Prosun
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik.
    Spatial, vertical and temporal variation of arsenic in shallow aquifers of the Bengal Basin: Controlling geochemical processes2014Inngår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 387, s. 157-169Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A detailed understanding of the geochemical processes that regulate the spatial, temporal and vertical variation of dissolved arsenic (As) in shallow aquifers (<50 m) is a prerequisite for sustainable drinking water management in the Bengal Basin. The present study conducted at Chakdaha Block of the Nadia District, West Bengal, India, combined a high resolution hydrogeochemical monitoring study over 20 months from two sets of piezometers (2 x 5) to the sediment geochemistry at areas with high (average:146 mu g/L, n = 5) and relatively low (average: 53.3 mu g/L, n = 10) dissolved As concentrations in groundwater. The determination of the isotopic composition of delta H-2 and delta O-18 in groundwater of the two sites indicated the recharge of evaporative surface water to the aquifer. The concentrations of major aqueous solutes (Ca2+, Mg2+, Na+, K+, HCO3- and Cl-) and electrical conductivity were considerably higher in wells at the high As site compared to the low As site. Additionally, at the high As site, the major ions, Fe, SO42-, electrical conductivity, delta H-2 and delta O-18 showed markedly greater enrichment in the shallowest part (<24 m) of the aquifer compared to the deeper part, reflecting vertical layering of groundwater composition within the aquifer. The oxidation of pyrites has been attributed to the high rate of mineral dissolution resulting in such greater enrichments in this part of the aquifer. In addition, the anthropogenic input with recharge water possibly increased the concentrations of Cl- in this part of the aquifer. The vertical layering of groundwater was absent in the aquifer at the low As site. The absence of such layering and relatively low major ion concentrations and electrical conductivity could be linked to the enhanced aquifer flushing and decreased water-ediment interactions influenced by local-scale groundwater abstraction. The seasonal variations of As concentrations in groundwater were observed only in the shallowest part of the aquifers (<30 m). Furthermore, the As concentrations in groundwater at the uppermost part of the shallow aquifers (<21 m) increased continuously over the monitoring period at both sites. This study supports the view that the reductive dissolution of Fe oxyhydroxides coupled with competitive PO43- sorption reactions in the aquifer sediment enriches As in groundwater of the Bengal Basin. However, the additional Fe released by the weathering of silicate minerals, especially biotite, or the precipitation of Fe as secondary mineral phases such as siderite, vivianite and acid volatile sulfides may result in the decoupling of As and Fe enrichment in groundwater. The redox zonation within the aquifer possibly regulates the vertical distribution of As in the groundwater.

  • 3.
    Gustafsson, Jon Petter
    KTH, Tidigare Institutioner, Mark- och vattenteknik.
    Modelling molybdate and tungstate adsorption to ferrihydrite2003Inngår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 200, nr 02-jan, s. 105-115Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The environmental geochemistry of molybdenum and tungsten is not well known. To enable predictions of Mo and W concentrations in the presence of ferrihydrite (hydrous ferric oxide), batch equilibrations were made with MoO42-, WO42-, o-phosphate (PO43-) and freshly prepared ferrihydrite suspensions in 0.01 M NaNO3 in the pH range from 3 to 10 at 25°C. The results showed that WO42- is adsorbed more strongly than MoO42- , and that both ions are able to displace PO43- from adsorption sites at low pH. Two models, the Diffuse Layer Model (DLM) and the CD-MUSIC Model (CDM), were tested in an effort to describe the data. In both models, the adsorption of MoO42- and WO42- could be described with the use of two monodentate complexes. One of these was a fully protonated complex, equivalent to adsorbed molybdic or tungstic acid, which was required to fit the data at low pH. This was found to be the case also for a data set with goethite. In competitive systems with PO43- , the models did not always provide satisfactory predictions. It was suggested this may be partly due to the uncertainty in the PO43- complexation constants.

  • 4.
    Gustafsson, Jon Petter
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Tiberg, Charlotta
    Molybdenum binding to soil constituents in acid soils: An XAS and modelling study2015Inngår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 417, s. 279-288Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Despite its importance as a trace element, the binding mechanisms of molybdenum in soils are not well known. In this study, we studied the binding of molybdenum onto selected soil samples, and we used X-ray absorption spectroscopy (XAS) to characterize the coordination of molybdenum on three important environmental sorbents: ferrihydrite (Fh), amorphous aluminium hydroxide (Al(OH)(3)) and fulvic acid. The X-ray near-edge structure (XANES) data showed that the added molybdenum(VI) was not reduced, although for the organic samples the coordination shifted from tetrahedral to octahedral. The EXAFS (extended X-ray absorption fine structure) analysis showed that molybdenum(VI) on Fh and Al(OH)(3) was dominated by edge-sharing bidentate complexes with Mo center dot center dot center dot Fe and Mo center dot center dot center dot Al distances of 2.80 and 2.62 angstrom, respectively. For ferrihydrite, there was a minor contribution from a corner-sharing bidentate complex at 3.55 angstrom. Further, geochemical modelling suggested an additional role of an outer-sphere complex at high pH. A sample from a spodic Bs horizon had XANES and EXAFS features similar to those of Mo sorbed to Al(OH)(3), highlighting the importance of Al(OH)(3)-type sorbents in this soil. However, in the studied organic samples molybdenum(VI) was present in a distorted octahedral configuration as an organic complex. The results were used to improve molybdenum binding reaction equilibrium constants in the CD-MUSIC model for ferrihydrite and in the Stockholm Humic Model. Collectively the results show that acid soils may contain sorbents able to bind molybdenum efficiently, and thus prevent its leaching to waters.

  • 5.
    Hertz, Hans M.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Bertilson, Michael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    von Hofsten, Olof
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Gleber, S.-C.
    Sedlmair, J.
    Thieme, J.
    Laboratory X-ray microscopy for high-resolution imaging of environmental colloid structure2012Inngår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 329, nr SI, s. 26-31Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Transmission X-ray microscopy is a uniquely suited technique for studies of environmental colloids since it allows imaging in aqueous media with high spatial resolution, presently down to the 20 nm range. Such nanoscale morphological description of these high-specific-surface-area compounds show promise for improved understanding of soils, sediments or groundwater aquifers. However, present high-quality X-ray microscopes are located at synchrotron radiation facilities resulting in limited applicability and accessibility for colloid scientists. Here we investigate the applicability of a laboratory-scale transmission X-ray microscope for studies of colloids of the environment. The microscope is based on a laser-plasma source in combination with multilayer and zone plate optics. Samples are held at atmospheric pressure in their natural wet state. We show images revealing the nano-scale morphology of the clay nontronite, soils such as chernozem and luvisol, and the mineral hematite, an iron oxide. Comparative studies of dried substances clearly show the need for imaging in the wet state. The image quality approaches that of synchrotron-based microscopes, albeit at longer exposure times. Stereo imaging is investigated as a means for giving 3D information with shorter exposure times than tomography requires. Finally the future development of the laboratory X-ray microscope is discussed, especially with regard to the reduction of exposure times.

  • 6.
    Kleja, Dan B.
    et al.
    Swedish University of Agricultural Sciences.
    van Schaik, Joris W. J.
    Swedish University of Agricultural Sciences.
    Persson, Ingmar
    Swedish University of Agricultural Sciences.
    Gustafsson, Jon Petter
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630).
    Characterization of iron in floating surface films of some natural waters using EXAFS2012Inngår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 326, s. 19-26Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Floating, iron bearing films have been observed in a wide range of environments, including wetlands, seep waters in ground water discharge areas, small rivers and lakes. To date, knowledge about their formation and composition is scarce. We have investigated the form of iron in floating iron-rich films of different origin, including a pond and a brook, as well as seep water pools of a groundwater discharge area. Sampling sites were located in southern (pond, brook) and central (seep pools) Sweden. Synchrotron-based X-ray absorption spectroscopy (EXAFS and XANES) allowed identification of the iron precipitates present in the films, without any pretreatment. The EXAFS data showed that the iron containing phase formed in the floating films varied in composition between the sites investigated. In the films from two ground water discharge areas, characterized by out-flowing iron(II) rich ground water being high in pH and low in DOC, the iron phase was completely dominated by ferrihydrite. In contrast, surface films sampled from the brook and the pond, the iron speciation showed a mixture of iron(III)-organic complexes and iron (hydr)oxide (most likely ferrihydrite). These waters were oxic and contained higher concentration of DOC than the seep water pools in the ground water discharge areas. The position of the pre-edge peak, which is sensitive to the oxidation state of iron, did not indicate occurrence of iron (II) in any of the films. Elemental composition of one film (seep water), suggested that films contained about one third of organic matter. Ferrihydrite is probably present as small particles with humic material sorbed onto surfaces or included in the particles, making the particles sufficiently hydrophobic to not settle without physical disturbance. The films are fragile and break easily down and become suspended upon disturbance. More studies are warranted in order to understand the mechanism of the formation of these fascinating films and their biogeochemical role.

  • 7. Neidhardt, H.
    et al.
    Berner, Z. A.
    Freikowski, D.
    Biswas, Ashis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Majumder, S.
    Winter, J.
    Gallert, C.
    Chatterjee, D.
    Norra, S.
    Organic carbon induced mobilization of iron and manganese in a West Bengal aquifer and the muted response of groundwater arsenic concentrations2014Inngår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 367, s. 51-62Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The exact circumstances that cause the widespread enrichment of Mn and As in groundwater of the Bengal Delta Plain (BDP) and many other Asian delta areas still remain a matter of debate in the scientific community. We conducted an in situ field experiment in the central BDP region to investigate the influence of organic matter on the mobility of Fe, Mn and As in shallow aquifers. The groundwater at our study site was initially characterized by a circum-neutral pH, low concentrations of O2, NO3 - and SO4 2-, and increased Fe, Mn and As concentrations, reflecting reducing conditions in the aquifer. Since organic matter controls microbially mediated redox processes which are believed to result in the mobilization of Fe, Mn and As from Holocene aquifer sediments, an easily degradable carbon source (sucrose) was introduced into a shallow aquifer via four nested monitoring wells and distributed by circular pumping. Initial sucrose concentrations reached up to 2.55mM in the local groundwater and induced a strong increase in the activity of indigenous microbes that decomposed the sucrose within the following 14days stepwise into intermediate catabolic products (e.g., acetic acid), and finally to CO2/HCO3 -. The formation of organic acids was accompanied by a temporary decline in the pH and the redox potential, as well as an increase in the concentration of most major and trace elements in the groundwater by several times. While Mn concentrations rose up to 81.3μM (representing a 7.5 fold increase), Fe (on average 96.7% Fe(II)) concentrations reached a considerable transient maximum of 1390μM, which was 36 times higher than the initial baseline value. The most significant observation of this experiment is that the relative increments of dissolved As (on average 95.8% As(III)) reached between 19 and 49% only, which is in clear contrast to the pronounced mobilization of Fe, Mn and other trace elements. Changes in the groundwater composition during the experiment imply that the mobilization of Fe and Mn was primarily caused by a reductive dissolution of Mn-oxides and Fe-(oxyhydr)oxides, resulting from the stimulation of indigenous bacteria by the addition sucrose. In this context, the release of As can be attributed to the dissolution of Fe-(oxyhydr)oxides, which constitute the principal source of As in the aquifer sediments according to mineralogical and geochemical analyses. In contrast to the pronounced mobilization of Fe, the response of groundwater arsenic concentrations appeared to be muted, as indicated by subsequently declining As to Fe mol ratios that dropped one order in magnitude. The remarkable decoupling of As from Fe mobilization indicates that the aquifer sediments were apparently capable of compensating for the additional release of As. We attribute this As buffer potential to remaining Fe-minerals and potentially newly formed Fe(II)- and mixed Fe(II/III)-mineral phases, which were able to readily immobilize dissolved As. Sequential extraction results of the initial aquifer sediments further support this interpretation, revealing that up to 85% of the total As in the sediments was already present in adsorbed form, with Fe-minerals as principal hosts. Hence, the experimental data implies that a biogeochemically controlled environment of competing As release and retention arose after the addition of sucrose, where Fe-mineral phases played a key role in buffering the release of As. We further conclude that organic carbon limited aquifer systems in the BDP with increased As concentrations in groundwater may exhibit an unexpected buffer potential towards an additional As release, even when vast amounts of easily degradable organic carbon are introduced into the system.

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