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  • 1.
    Belonoshko, Anatoly
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Rosengren, Anders
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Iron shear modulus in the Earth's inner core2010In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 74, no 12, p. A75-A75Article in journal (Other academic)
  • 2.
    Berglund, S
    et al.
    KTH.
    Malmstrom, M E
    KTH.
    Jarsjo, J
    Destouni, G
    Modelling field-scale dispersion in heterogeneous groundwater systems with multi-component reactions2004In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 68, no 11, p. A456-A456Article in journal (Other academic)
  • 3.
    Dubois, Isabelle
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Zazzi, Åsa
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Malmström, Maria E.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Nickel sorption on chlorite: Batch experiments and modeling2009In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 73, no 13, p. A309-A309Article in journal (Refereed)
  • 4. Fedorov, Yu. N.
    et al.
    Maslov, A. V.
    Ronkin, Yu. L.
    Kutcherov, Vladmir G.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Alekseev, V. P.
    Geochemical investigation of crude oil samples from West Siberia Megabasin2010In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 74, no 12, p. A283-A283Article in journal (Other academic)
  • 5.
    Gustafsson, Jon Petter
    et al.
    KTH, Superseded Departments (pre-2005), Land and Water Resources Engineering.
    Berggren, D
    Salt effects on proton and cadmium binding to natural organic matter2004In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 68, no 11, p. A368-A368Article in journal (Other academic)
  • 6.
    Gustafsson, Jon Petter
    et al.
    KTH.
    Van Schaik, J. W. J.
    Kleja, Dan Berggren
    KTH.
    Persson, I.
    Mechanisms of iron(III) binding to organic matter and its competitive effect on trace metals2007In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 71, no 15, p. A364-A364Article in journal (Other academic)
  • 7. Jacks, G.
    et al.
    Harikumar, P. S.
    CWRDM, Kozhikode 673571, Kerala, India..
    Bhattacharya, Prosun
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Fluoride mobilisation in India2009In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 73, no 13, p. A578-A578Article in journal (Other academic)
  • 8.
    Jakariya, M.
    et al.
    NGO Forum Drinking Water Supply & Sanitat, Dhaka 1207, Bangladesh..
    Rahman, S. N.
    NGO Forum Drinking Water Supply & Sanitat, Dhaka 1207, Bangladesh..
    Bhattacharya, Prosun
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Rahman, M.
    ICDDR B Ctr, Dhaka, Bangladesh..
    von Bromssen, M.
    KTH, School of Architecture and the Built Environment (ABE).
    Persson, L. -A
    Uppsala Univ, IMCH, Uppsala, Sweden..
    Vahter, M.
    Karolinska Inst, Inst Environm Med, S-10401 Stockholm, Sweden..
    Temporal and seasonal variation in tubewell water arsenic concentrations in Matlab, Bangladesh2009In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 73, no 13, p. A583-A583Article in journal (Other academic)
  • 9. Kleja, D. B.
    et al.
    Standring, W.
    Oughton, D. H.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Fifield, K.
    Fraser, A. R.
    Assessment of isotopically exchangeable Al in soil materials using Al-26 tracer2005In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 69, no 22, p. 5263-5277Article in journal (Refereed)
    Abstract [en]

    The solubility of aluminium (Al) in many acidic soils is controlled by complexation reactions with soil organic matter. In such soils, Al solubility is theoretically a function of the pool size of active Al, i.e., the total amount of Al that equilibrates with the sod solution within a defined period of time. To date, no reliable measurements of active Al in soil materials exist. In this study, we determined the isotopically exchangeable pool of Al (E-A1) as an operationally defined assessment of active Al in acidic mineral soils. The suitability of CuCl2 and pyrophosphate (Na4P2O7) as extractants for active Al was also evaluated. Eleven samples, mostly from spodic B horizons, were spiked with carrier-free Al-26 and equilibrated for different time periods (1-756 h). The size of the Al pool with which the Al-26 tracer exchanged increased with time during the whole experimental period. Thus, contact time between solid and solution phases needs to be defined when assessing the active Al pool. Values of E-A1 obtained after I to 5 d of equilibration were equal to the amount of CuCl2 extractable Al, but considerably smaller than the Na4P2O7-extractable pool. Equilibration times greater than 5 d resulted in CuCl2 extractable Al concentrations that under-estimated the active Al pool. Three of the investigated samples were rich in imogolite-type materials (ITM). In these samples, 30-50 % of the added Al-26 rapidly became associated with soil constituents in forms that could not be extracted by Na4P2O7, indicating that a part of ITM may be in a dynamic state.

  • 10. Kleja, Dan B.
    et al.
    Van Schaik, Joris
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Acid-base and copper binding properties of three organic matter fractions isolated from a soil solution2009In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 73, no 13, p. A667-A667Article in journal (Refereed)
  • 11.
    Kutcherov, Vladmir G.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Abyssal abiogenic origin of petroleum: Updated milestones2010In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 74, no 12, p. A551-A551Article in journal (Other academic)
  • 12.
    Malmström, Maria
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Destouni, G.
    Berglund, S.
    Spreading Versus Mixing Effects on Reactive Transport in Groundwater2005In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 69, no 10, p. A176-A176Article in journal (Other academic)
  • 13.
    Malmström, Maria
    et al.
    KTH, Superseded Departments, Civil and Environmental Engineering.
    Salmon, Sally
    KTH, Superseded Departments, Civil and Environmental Engineering.
    Mineral Weathering Rates in Sulphidic Mill Tailings: Do Rate Laws for Monomineralic Samples Apply?2004In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 68, no 11, p. A147-A147Article in journal (Other academic)
  • 14.
    Norrström, Ann-Catrine
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Somerville, Richard
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Low-cost adsorption media for removal of toxic metals from contaminated water2009In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 73, no 13, p. A953-A953Article in journal (Other academic)
  • 15. Routh, J.
    et al.
    Saraswathy, A.
    Bhattacharya, A.
    Nag, S.K.
    Ray, S.P.S.
    Jacks, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Arsenic reduction by bacteria in shallow aquifers from Ambikanagar in West Bengal, India2006In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 68, no 11, p. A515-Article in journal (Other academic)
  • 16.
    Shaw, Cliff S. J.
    et al.
    Univ New Brunswick, Dept Earth Sci, 2 Bailey Dr, Fredericton, NB E3C 1G1, Canada..
    Klausen, Kim B.
    Univ New Brunswick, Dept Earth Sci, 2 Bailey Dr, Fredericton, NB E3C 1G1, Canada..
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Kinetics of dissolution of sapphire in melts in the CaO-Al2O3-SiO2 system2018In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 229, p. 129-146Article in journal (Refereed)
    Abstract [en]

    The dissolution rate of sapphire in melts in the CAS system of varying silica activity, viscosity and degree of alumina saturation has been determined at 1600 degrees C and 1.5 GPa. After an initiation period of up to 1800 s, dissolution is controlled by diffusion of cations through the boundary layer adjacent to the dissolving sapphire. The dissolution rate decreases with increasing silica activity, viscosity and molar Al2O3/CaO. The calculated diffusion matrix for each solvent melt shows that CAS 1 and 9 which have molar Al2O3/CaO of 0.33 and 0.6 and dissolution rate constants of 0.65 x 10(-6) and 0.59 x 10(-6) m/s(0.5) have similar directions and magnitudes of diffusive coupling: DCaO-Al2O3 and DAl2O3-CaO are both negative are approximately equal. The solvent with the fastest dissolution rate: CAS 4, which has a rate constant of 1.5 x 10(-6) m/s(0.5) and Al2O3/CaO of 0.31 has positive DCaO-Al2O3 and negative DAl2O3-CaO and the absolute values vary by a factor of 4. Although many studies show that aluminium is added to the melts via the reaction: Si4+ = Al3+ + 0.5 Ca2+ the compositional profiles show that this reaction is not the only one involved in accommodating the aluminium added during sapphire dissolution. Rather, aluminium is incorporated as both tetrahedrally coordinated Al charge balanced by Ca and as aluminium not charge balanced by Ca (termed Al-xs). This reaction: Al-IV-Ca = Al-xs thorn Ca-NBO where Ca-NBO is a non-bridging oxygen associated with calcium, may involve the formation of aluminium triclusters. The shape of the compositional profiles and oxide-oxide composition paths is controlled by the aluminium addition reaction. When Al-xs exceeds 2%, CaO diffusion becomes increasingly anomalous and since the bond strength of Al-xs correlates with CaO/CaO + Al2O3, the presence of more than 2% Al-xs leads to significantly slower dissolution than when Al-xs is absent or at low concentration. Thus, dissolution is controlled by diffusion of cations through the boundary layer, but this diffusion is itself controlled by the structural modifications required by the addition of new components to the melt. Comparison of quartz dissolution rates in similar melts shows that dissolution is much faster for quartz than for sapphire and that dissolution rates show the same correlation with silica activity and viscosity. We suggest that diffusive fluxes are related to changes in melt structure and the nature of the reaction that incorporates the added component. For the slow eigendirection, SiO2 addition occurs by a single reaction whereas Al2O3 addition requires a more complex two part reaction in which Al is accommodated by charge balance with Ca until Al is in excess of that which can be charge balanced. The Al-xs incorporation reaction, is slower than the Si incorporation reaction which inhibits sapphire dissolution relative to quartz in melts of the same composition.

  • 17.
    Sjöstedt, Carin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Persson, I.
    Berggren Kleja, Dan
    SGI.
    Hassellöv, Martin
    Göteborgs Universitet, Institutionen för Kemi.
    Borg, Hans
    Stockholms Universitet, ITM.
    Iron phases in soils and softwater lakes as determined by EXAFS spectroscopy2010In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 74, no 12, p. A969-A969Article in journal (Other academic)
  • 18.
    Sjöstedt, Carin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Persson, Ingmar
    SLU.
    Hesterberg, Dean
    Department of Soil Science, North Carolina State University.
    Berggren Kleja, Dan
    SGI.
    Borg, Hans
    Stockholms Universitet, ITM.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Iron speciation in soft-water lakes and soils as determined by EXAFS spectroscopy and geochemical modelling2013In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 105, p. 172-186Article in journal (Refereed)
    Abstract [en]

    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.

  • 19.
    Tiberg, Charlotta
    et al.
    Swedish University of Agricultural Sciences (SLU), Sweden.
    Sjöstedt, Carin
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Persson, Ingmar
    Swedish University of Agricultural Sciences (SLU), Sweden.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Phosphate effects on copper(II) and lead(II) sorption to ferrihydrite2013In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 120, p. 140-157Article in journal (Refereed)
    Abstract [en]

    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.

  • 20. van Schaik, Joris W. J.
    et al.
    Kleja, Dan B.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Environmental Geochemistry and Ecotechnology.
    Acid-base and copper-binding properties of three organic matter fractions isolated from a forest floor soil solution2010In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 74, no 4, p. 1391-1406Article in journal (Refereed)
    Abstract [en]

    Vast amounts of knowledge about the proton- and metal-binding properties of dissolved organic matter (DOM) in natural waters have been obtained in studies on isolated humic and fulvic (hydrophobic) acids. Although macromolecular hydrophilic acids normally make up about one-third of DOM, their proton- and metal-binding properties are poorly known. Here, we investigated the acid-base and Cu-binding properties of the hydrophobic (fulvic) acid fraction and two hydrophilic fractions isolated from a soil solution. Proton titrations revealed a higher total charge for the hydrophilic acid fractions than for the hydrophobic acid fraction. The most hydrophilic fraction appeared to be dominated by weak acid sites, as evidenced by increased slope of the curve of surface charge versus pH at pH values above 6. The titration curves were poorly predicted by both Stockholm Humic Model (SHM) and NTCA-Donnan model calculations using generic parameter values, but could be modelled accurately after optimisation of the proton-binding parameters (pH <= 9). Cu-binding isotherms for the three fractions were determined at pH values of 4, 6 and 9. With the optimised proton-binding parameters, the SHM model predictions for Cu binding improved, whereas the NICA-Donnan predictions deteriorated. After optimisation of Cu-binding parameters, both models described the experimental data satisfactorily. Iron(III) and aluminium competed strongly with Cu for binding sites at both pH 4 and pH 6. The SHM model predicted this competition reasonably well, but the NICA-Donnan model underestimated the effects significantly at pH 6. Overall, the Cu-binding behaviour of the two hydrophilic acid fractions was very similar to that of the hydrophobic acid fraction, despite the differences observed in proton-binding characteristics. These results show that for modelling purposes, it is essential to include the hydrophilic acid fraction in the pool of 'active' humic substances.

  • 21. Wolthers, Mariette
    et al.
    Nehrke, Gernot
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Environmental Geochemistry and Ecotechnology.
    Van Cappellen, Philippe
    Calcite growth kinetics: Modeling the effect of solution stoichiometry2012In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 77, p. 121-134Article in journal (Refereed)
    Abstract [en]

    Until recently the influence of solution stoichiometry on calcite crystal growth kinetics has attracted little attention, despite the fact that in most aqueous environments calcite precipitates from non-stoichiometric solution. In order to account for the dependence of the calcite crystal growth rate on the cation to anion ratio in solution, we extend the growth model for binary symmetrical electrolyte crystals of Zhang and Nancollas (1998) by combining it with the surface complexation model for the chemical structure of the calcite-aqueous solution interface of Wolthers et al. (2008). To maintain crystal stoichiometry, the rate of attachment of calcium ions to step edges is assumed to equal the rate of attachment of carbonate plus bicarbonate ions. The model parameters are optimized by fitting the model to the step velocities obtained previously by atomic force microscopy (AFM, Teng et al., 2000; Stack and Grantham, 2010). A variable surface roughness factor is introduced in order to reconcile the new process-based growth model with bulk precipitation rates measured in seeded calcite growth experiments. For practical applications, we further present empirical parabolic rate equations fitted to bulk growth rates of calcite in common background electrolytes and in artificial seawater-type solutions. Both the process-based and empirical growth rate equations agree with measured calcite growth rates over broad ranges of ionic strength, pH, solution stoichiometry and degree of supersaturation.

  • 22. Åström, Mats E.
    et al.
    Nystrand, Miriam
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Österholm, Peter
    Nordmyr, Linda
    Reynolds, Jason K.
    Peltola, Pasi
    Lanthanoid behaviour in an acidic landscape2010In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 74, no 3, p. 829-845Article in journal (Refereed)
    Abstract [en]

    Lanthanoids were studied in a boreal landscape where an abundance of acid sulfate soils and Histosols provide a unique opportunity to increase the understanding of flow these metals behave in acidic soils and waters and interact with soil and aqueous organic matter. In the acid sulfate soils lanthanoids are mobile as reflected in high to very high concentrations in soil water and runoff (typically a few mg 1(-1) but Lip to 12 mg 1(-1)) and abundant release by several relatively weak extractants (ammonium acetate EDTA, sodium pyrophosphate, hydroxylamine hydrochloride) applied on bulk soil. Normalisation with the lanthanoid pool in the underlying parent materials (sulphide-bearing sediments deposited in brackish-water) and soil water showed that the extensive release/retention in the acidic soil was accompanied by large, and variable, fractionation trends across the lanthanoid series. In low-order streams draining these soils, the lanthanoid concentrations were high and, as indicated by frontal ultrafiltration and geochemical modelling, largely dissolved (<1 kDa) in the form of the species LnSO(4)(+) and Ln(3+). In other moderately acidic stream waters (pH 4.3-4.6), organic complexation was predicted to be important in the <1 kDa fraction (especially for the heavy lanthanoids) and strongly dominating in the colloidal phase (1 kDa-0.45 mu m). Along the main stem of a stream in focus (catchment area of 223 km(2)), lanthanoid concentrations increased downstream, in particular during high flows, caused by a downstream increase in the proportion of acid sulfate soils which are extensively flushed during wet periods. The geochemical models applied to the colloidal Ln-organic phase were not successful in predicting the measured fractionation patterns.

  • 23. Åström, Mats E.
    et al.
    Österholm, Peter
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Nystrand, Miriam
    Peltola, Pasi
    Nordmyr, Linda
    Boman, Anton
    Attenuation of rare earth elements in a boreal estuary2012In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 96, p. 105-119Article in journal (Refereed)
    Abstract [en]

    This study focuses on attenuation of rare earth elements (REE) when a boreal creek, acidified and loaded with REE and other metals as a result of wetland drainage, empties into a brackish-water estuary (salinity < 6 parts per thousand). Surface water was collected in a transect from the creek mouth to the outer estuary, and settling (particulate) material in sediment traps moored at selected locations in the estuary. Ultrafiltration, high-resolution ICP-MS and modeling were applied on the waters, and a variety of chemical reagents were used to extract metals from the settling material. Aluminium, Fe and REE transported by the acidic creek were extensively removed in the inner/central estuary where the acidic water was neutralised, whereas Mn was relatively persistent in solution and thus redistributed to particles and deposited further down the estuary. The REE removal was caused by several contemporary mechanisms: co-precipitation with oxyhydroxides (mainly Al but also Fe), complexation with flocculating humic substances and sorption to suspended particles. Down estuary the dissolved REE pool, remaining after removal, was fractionated: the < 1 kDa pool became depleted in the middle REE and the colloidal (0.45 mu m-1 kDa) pool depleted in the middle and heavy REE. This fractionation was controlled by the removal process, such that those REE with highest affinity for the settling particles became most depleted in the remaining dissolved pool. Modeling, based on Visual MINTEQ version 3.0 and the Stockholm Humic Model after revision and updating, predicted that the dissolved (< 0.45 mu m) REE pool in the estuary is bound almost entirely to humic substances. Acid sulphate soils, the source of the REE and other metals in the creek water, are widespread on coastal plains worldwide and therefore the REE attenuation patterns and mechanisms identified in the studied estuary are relevant for recognition of similar geochemical processes and conditions in a variety of coastal locations.

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