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  • 1.
    Adediran, Gbotemi A.
    et al.
    Swedish Univ Agr Sci, Dept Soil & Environm, Box 7014, S-75007 Uppsala, Sweden..
    Tuyishime, J. R. Marius
    Swedish Univ Agr Sci, Dept Soil & Environm, Box 7014, S-75007 Uppsala, Sweden..
    Vantelon, Delphine
    Synchrotron SOLEIL, St Aubin BP 48, F-91192 Gif Sur Yvette, France..
    Klysubun, Wantana
    Synchrotron Light Res Inst, 111 Moo 6, Muang, Nakhon Ratchasi, Thailand..
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. Swedish Univ Agr Sci, Dept Soil & Environm, Box 7014, S-75007 Uppsala, Sweden..
    Phosphorus in 2D: Spatially resolved P speciation in two Swedish forest soils as influenced by apatite weathering and podzolization2020In: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 376, article id 114550Article in journal (Refereed)
    Abstract [en]

    The cycling and long-term supply of phosphorus (P) in soils are of global environmental and agricultural concern. To advance the knowledge, a detailed understanding of both the vertical and lateral variation of P chemical speciation and retention mechanism(s) is required, a knowledge that is limited in postglacial forest soils. We combined the use of synchrotron X-ray fluorescence microscopy with multi-elemental co-localisation analysis and P K-edge XANES spectroscopy to reveal critical chemical and structural soil properties. We established a two-dimensional (2D) imagery of P retention and speciation at a microscale spatial resolution in two forest soil profiles formed in glaciofluvial and wave-washed sand. The abundance and speciation of P in the upper 40 cm was found to be influenced by soil weathering and podzolization, leading to spatial variability in P speciation on the microscale (< 200 pm) with P existing predominantly as organic P and as PO4 adsorbed to allophane and ferrihydrite, according to XANES spectroscopy. These species were mostly retained at sharp edges and in pore spaces within Al and Si-bearing particles. Despite the relatively young age ( < 15,000 years) of the soils, our results show primary mineral apatite to have weathered from the surface horizons. In the C horizon however, a large fraction of the P was in the form of apatite, which appeared as widely dispersed ( > 600 pm) hot spots of inclusions in aluminosilicates or as discrete micro-sized apatite grains. The subsoil apatite represents a pool of P that trees can potentially acquire and thus add to the biogeochemically active P pool in temperate forest soils.

  • 2.
    Apul, Defne S.
    et al.
    Department of Civil Engineering, University of Toledo.
    Diaz, Maria E.
    Department of Chemical Engineering, University of Toledo.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Hundal, Lakhwinder S.
    Metropolitan Water Reclamation District of Greater Chicago, Research and Development Department, Section 123.
    Geochemical Modeling of Trace Element Release from Biosolids2010In: Environmental Engineering Science, ISSN 1092-8758, E-ISSN 1557-9018, Vol. 27, no 9, p. 743-755Article in journal (Refereed)
    Abstract [en]

    Biosolids-borne trace elements may be released to the environment when biosolids are used as fertilizers in farm land. Trace element leachate concentrations from biosolids are known to be limited by both organic and inorganic sorbent surfaces; this experimental evidence has not been previously verified with geochemical modeling of sorption reactions. In this study, pH-dependent leaching experiments and sorption isotherm experiments were coupled with a multisurface geochemical modeling approach. Biosolids samples were obtained from Toledo and Chicago wastewater treatment plants; their sorbent surfaces were defined and modeled as a combination of organic matter (OM) and Fe-, Al-, and Mn-oxides. The multisurface geochemical modeling approach was partially successful in predicting the pH-dependent leachate concentrations of As, Cd, Cr, Cu, Mo, Ni, and Zn. Both modeled and experimental data indicated that As and Mo in biosolids were bound to Fe- oxides; Cd, Cr, and Cu were bound mainly to OM; and as pH increased the fractions of Cd and Cu bound to Fe- oxides in the biosolids matrix increased. Ni and Zn were distributed between OM and Fe- oxides, and the percentage of each fraction depended on the pH. This study showed that the multisurface geochemical model could be used to generate As (and to a lesser extent Cd) Freundlich isotherm parameters for biosolids. However, the composition and reactivity of solid and dissolved OM was identified as a source of uncertainty in the modeling results. Therefore, more detailed studies focusing on the reactivity of isolated biosolids OM fractions with regard to proton and metal binding are needed to improve the capability of geochemical models to predict the fate of biosolids-borne trace metals in the environment.

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  • 3.
    Aullón Alcaine, Anna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Schulz, Carlos
    Univ Nacl La Pampa UNLPam, Fac Ciencias Exactas & Nat, Av Uruguay 151,L6300, Santa Rosa, La Pampa, Argentina..
    Bundschuh, Jochen
    Univ Southern Queensland, UNESCO Chair Groundwater Arsen Agenda Sustainable, West St, Toowoomba, Qld 4350, Australia.;Univ Southern Queensland, Fac Hlth Engn & Sci, West St, Toowoomba, Qld 4350, Australia..
    Jacks, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Thunvik, Roger
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Mörth, Carl-Magnus
    Stockholm Univ, Dept Geol & Geochem, Stockholm, Sweden..
    Sracek, Ondra
    Palacky Univ, Fac Sci, Dept Geol, 17 Listopadu 12, Olomouc 777146, Czech Republic..
    Ahmad, Arslan
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Bhattacharya, Prosun
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Hydrogeochemical controls on the mobility of arsenic, fluoride and other geogenic co-contaminants in the shallow aquifers of northeastern La Pampa Province in Argentina2020In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 715, article id 136671Article in journal (Refereed)
    Abstract [en]

    Elevated Arsenic (As) and Fluoride (F) concentrations in groundwater have been studied in the shallow aquifers of northeastern of La Pampa province, in the Chaco-Pampean plain, Argentina. The source of As and co-contaminants is mainly geogenic, from the weathering of volcanic ash and loess (rhyolitic glass) that erupted from the Andean volcanic range. In this study we have assessed the groundwater quality in two semi-arid areas of La Pampa. We have also identified the spatial distribution of As and co-contaminants in groundwater and determined the major factors controlling the mobilization of As in the shallow aquifers. The groundwater samples were circum-neutral to alkaline (7.4 to 92), oxidizing (Eh similar to 0.24 V) and characterized by high salinity (EC = 456-11,400 mu S/cm) and Na+-HCO3- water types in recharge areas. Carbonate concretions ("tosca") were abundant in the upper layers of the shallow aquifer. The concentration of total As (5.6 to 535 mu g/L) and F (0.5 to 14.2 mg/L) were heterogeneous and exceeded the recommended WHO Guidelines and the Argentine Standards for drinking water. The predominant As species were arsenate As(V) oxyanions, determined by thermodynamic calculations. Arsenic was positively correlated with bicarbonate (HCO3-), fluoride (F), boron (B) and vanadium (V), but negatively correlated with iron (Fe), aluminium (Al), and manganese (Mn), which were present in low concentrations. The highest amount of As in sediments was from the surface of the dry lake. The mechanisms for As mobilization are associated with multiple factors: geochemical reactions, hydrogeological characteristics of the local aquifer and climatic factors. Desorption of As(V) at high pH, and ion competition for adsorption sites are considered the principal mechanisms for As mobilization in the shallow aquifers. In addition, the long-term consumption of the groundwater could pose a threat for the health of the local community and low cost remediation techniques are required to improve the drinking water quality.

  • 4. Baken, S.
    et al.
    Larsson, M. A.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Cubadda, F.
    Smolders, E.
    Ageing of vanadium in soils and consequences for bioavailability2012In: European Journal of Soil Science, ISSN 1351-0754, E-ISSN 1365-2389, Vol. 63, no 6, p. 839-847Article in journal (Refereed)
    Abstract [en]

    Total vanadium (V) concentrations in soils commonly range from 20 to 120 mg kg-1. Vanadium added directly to soils is more soluble than geogenic V and can be phytotoxic at doses within this range of background concentrations. However, it is unknown how slow sorption reactions change the fate and effect of added V in soils. This study addresses the changes in V solubility, toxicity and bioavailability in soils over time. Four soils were amended with pentavalent V in the form of a soluble vanadate salt, and extractable V concentrations were monitored over 100 days. The toxicity to barley and tomato plants was evaluated in freshly spiked soils and in the corresponding aged soils that were equilibrated for up to 330 days after spiking. The V concentrations in 0.01 m CaCl2 soil extracts decreased approximately two-fold between 14 and 100 days after soil spiking, and the reaction kinetics were similar for all soils. The phytotoxicity of added V decreased on average two-fold between freshly spiked and aged soils. The reduced toxicity was associated with a corresponding decrease in V concentrations in the isolated soil solutions and in the shoots. The V speciation in the soil solution of the aged soils was dominated by V(V); less than 8% was present as V(IV). Oxalate extractions suggest that the V(V) added to soils is predominantly sorbed onto poorly crystalline oxyhydroxides. It is concluded that the toxicity of V measured in freshly spiked soils may not be representative of soils subject to a long-term V contamination in the field.

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  • 5.
    Baken, Stijn
    et al.
    KU Leuven, Belgium.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Smolders, Erik
    KU Leuven, Belgium.
    The association between iron and carbon in freshwater colloids2013Conference paper (Refereed)
    Abstract [en]

    Iron and carbon are important constituents of natural colloids, which intimately links the fate of these two elements in riverine systems. Iron may strongly affect the binding of trace metals by organic matter, e.g. through competition for binding sites, which highlights the importance of a correct appreciation of the Fe speciation in surface waters. However, the chemistry of Fe and C in natural colloids is complex and depend on many factors including the pH, the Fe:C ratio, and the redox speciation of Fe [1-3]. Two areas with a contrasting Fe chemistry were studied: a lowland area with widespread seepage of iron-rich groundwater, and an upland peat area. Samples of ten oxic, well-mixed streams were subjected to cascade filtration using conventional filtration (1.2 µm, 0.45 µm, 0.1 µm) and cross-flow ultrafiltration (CFF; 5 kDa). The colloidal fraction, here operationally defined as between 0.45 µm and 5 kDa, was isolated by CFF and subsequently freeze-dried. The speciation of colloidal Fe was determined by EXAFS spectroscopy at the Fe K-edge (MAX-lab, Lund, Sweden). In the rivers draining upland peat, Fe and C were predominantly recovered in the fraction between 5 kDa and 0.1 µm. Conversely, in the rivers draining the lowland with extensive seepage of iron-rich groundwater, Fe was most abundant in the > 0.1 µm fraction, whereas C was predominantly present < 0.1 µm. The EXAFS data reveal that colloidal Fe speciation is different in both study areas. It exists as mononuclear Fe complexed by dissolved organic matter, as colloidal hydrous ferric oxides (likely stabilized by adsorbed organic matter), or as a mixture of these. The colloidal Fe concentrations show considerable seasonal variability. Overall, this study contributes to a better understanding of colloidal Fe speciation and of its interaction with organic C.

  • 6. Baken, Stijn
    et al.
    Sjöstedt, Carin
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Seuntjens, Piet
    Desmet, Nele
    De Schutter, Jan
    Smolders, Erik
    Characterisation of hydrous ferric oxides derived from iron-rich groundwaters and their contribution to the suspended sediment of streams2013In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 39, p. 59-68Article in journal (Refereed)
    Abstract [en]

    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.

  • 7. Berger, T.
    et al.
    Mathurin, F. A.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. Swedish University of Agricultural Sciences, Sweden.
    Peltola, P.
    Åström, M.E.
    The impact of fluoride on Al abundance and speciation in boreal streams2015In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 409, p. 118-124Article in journal (Refereed)
    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.

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  • 8.
    Berggren Kleja, Dan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Elert, Mark
    Kemakta Konsult AB.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Jarvis, las
    Markvetenskap, SLU.
    Norrström, Ann-Catrine
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Metallers mobilitet i mark2006Report (Refereed)
    Abstract [sv]

    I rapporten beskrivs nuvarande kunskapsläge när det gäller metallers uppträdande imark. Riskbedömningar för metaller i förorenad mark diskuteras.De flesta metaller binds i viss utsträckning i marken, oftast genom olika ytreaktioner med markens organiska material eller med järn- och aluminiumoxider, ochibland även genom utfällningsreaktioner. I vilken omfattning detta sker beror avfaktorer som t.ex. pH, redoxförhållanden, löst organiskt material (DOC) i markvattnet, samt förekomst av konkurrerande joner. Det är också viktigt att beaktavilka former metallerna förekommer som i markvattnet. Komplexbildning medt.ex. DOC minskar i regel toxiciteten. För att bättre ta hänsyn till markkemiskaförhållanden i riskbedömningen bör geokemiska modeller komma till ökad användning.Metaller lösta i vattnet följer med när vattnet strömmar och kan transporterastill grund- och ytvatten eller tas upp av växter. Hur snabbt detta går beror, förutomkemiska och biologiska processer, även på en rad olika jordegenskaper. Till exempel innehåller vissa jordar s.k. makroporer vilka ger upphov till preferentiellt flöde.Detta innebär att en del av metallerna snabbare kan transporteras genom marken,förbi jordpartiklar där metallerna annars skulle bindas.De olika modeller som används för att beskriva påverkan av markförorening pågrundvatten kan delas in i två grupper: stationära modeller antar att källtermen ärkonstant och tar enbart hänsyn till den utspädning som sker i grundvattnet. Exempel på sådana modeller är den svenska riktvärdesmodellen, JAGG och RBCA. I detvå senare modellerna finns möjlighet att ta hänsyn till nedbrytning av organiskaämnen. Tidsberoende modeller antar en avklingande källterm och en tidsberoendetransport i grundvattnet, exempelvis RISC och TAC-modellen. För beräkning avtransport i grundvattnet tas hänsyn till flödes- och fastläggningsmekanismer somadvektion, dispersion och linjär sorption.Med hjälp av laktester kan man uppskatta den andel av metallföroreningen somär löslig i vatten. Denna information kan sedan användas för att beräkna adsorptionsparametrar (Kd-värden, m.m.) för spridningsmodeller. Laktester kan ibland gemissvisande resultat eftersom de orsakar utspädning av provet, bl.a. blir DOCkoncentrationerna alltför låga. Dessutom bör de inte användas för sulfidjordar.Geokemiska modeller kan användas för att förbättra tolkningen av laktester för attfå till stånd realistiska uppskattningar av Kd-värden.Det finns ett antal spridningsmodeller som kan användas för att bedöma riskenför spridning till grundvatten och ytvatten. De är kraftfulla verktyg som dock ännuinte använts i någon större utsträckning i Sverige. Detta beror på flera orsaker, bl.a.de hydrogeologiska förhållandena i Sverige, behovet av anpassningen av de modeller som är allmänt tillgängliga, svårigheter att ta fram bra dataunderlag samt ensvag tradition i att använda modeller och förstå modellresultat.Ett par angelägna forsknings- och utvecklingsinsatser är att ta fram bättre uppskattningar av metalladsorption i svensk mark, och att anpassa existerande spridningsmodeller för användning i riskbedömningar.

  • 9.
    Bhattacharya, Prosun
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering. Swedish Univ Environm Sci, Dept Soil & Environm, Box 7014, S-75007 Uppsala, Sweden.
    Tribute to Gunnar Jacks (*April 13, 1937 dagger September 18, 2019)2019In: Environmental Earth Sciences, ISSN 1866-6280, E-ISSN 1866-6299, Vol. 78, no 24, article id 724Article in journal (Other academic)
  • 10.
    Biswas, Ashis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Neidhardt, H.
    Karlsruhe Institute of Technology, Germany.
    Halder, Dipti
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Kundu, A.K.
    University of Kalyani, India.
    Chatterjee, Debashis
    University of Kalyani, India.
    Berner, Z.
    Karlsruhe Institute of Technology, Germany.
    Bhattacharya, Prosun
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Surface complexation modeling of temporal variability of arsenic in groundwater: Estimating the role of competing ions in the mobilization processes2013Conference paper (Refereed)
    Abstract [en]

    This study investigates the relative roles of different competing ions on the mobilization of arsenic (As) by surface complexation modeling of As rich groundwater in the aquifer of Bengal Basin. Two sets of piezometers, installed at different depths of the shallow aquifer (<50 m), have been monitored for As and other relevant hydrogeochemical parameters over a period of 20 months. The potentiality of two different surface complexation models (SCM), developed for ferrihydrite and goethite has been explored to account for the observed temporal variation in As(III) and As(V) concentration in groundwater. The SCM for ferrihydrite appears as the better predictor for the observed variation in both As(III) and As(V) concentration. It is estimated that among the competing ions PO43- is the major competitor of As(III) and As(V) adsorption into Fe oxyhydroxide and competing ability of the ions decreases as PO43- >> Fe(II) > H4SiO4 = HCO3-. The result of sensitivity test indicates that the competition of PO43- with As for the adsorption sites might already reach nearly to the stage of maxima. It is also shown that a slight increase or decrease in pH can have overwhelming effect on the mobility of As(III) and As(V) by changing their concentration oppositely. It appears that only the reductive dissolution of Fe oxyhydroxide cannot explain the observed high As concentration in the groundwater of Bengal Basin. In absence of potential competition for the adsorption sites, As released due to reductive dissolution of Fe oxyhydroxide would have been re-adsorbed into the residual Fe phases. This study suggests that the reductive dissolution of Fe oxyhydroxide followed by competitive ion exchange with the aquifer sediment is the processes conducive for As enrichment in groundwater of the sedimentary aquifers.

  • 11.
    Biswas, Ashis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Neidhardt, Harald
    Halder, Dipti
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Kundu, Amit K.
    Chatterjee, Debashis
    Berner, Zsolt
    Bhattacharya, Prosun
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Role of competing ions in the mobilization of arsenic in groundwater of Bengal Basin: Insight from surface complexation modeling2014In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 55, p. 30-39Article in journal (Refereed)
    Abstract [en]

    This study assesses the role of competing ions in the mobilization of arsenic (As) by surface complexation modeling of the temporal variability of As in groundwater. The potential use of two different surface complexation models (SCMs), developed for ferrihydrite and goethite, has been explored to account for the temporal variation of As(III) and As(V) concentration, monitored in shallow groundwater of Bengal Basin over a period of 20 months. The SCM for ferrihydrite appears as the better predictor of the observed variation in both As(III) and As(V) concentrations in the study sites. It is estimated that among the competing ions, PO43- is the major competitor of As(III) and As(V) adsorption onto Fe oxyhydroxide, and the competition ability decreases in the order PO43- >> Fe(II) > H4SiO4 = HCO- (3.) It is further revealed that a small change in pH can also have a significant effect on the mobility of As(III) and As(V) in the aquifers. A decrease in pH increases the concentration of As(III), whereas it decreases the As(V) concentration and vice versa. The present study suggests that the reductive dissolution of Fe oxyhydroxide alone cannot explain the observed high As concentration in groundwater of the Bengal Basin. This study supports the view that the reductive dissolution of Fe oxyhydroxide followed by competitive sorption reactions with the aquifer sediment is the processes responsible for As enrichment in groundwater.

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  • 12.
    Biswas, Ashis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Neidhardt, Harald
    Halder, Dipti
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Kundu, Amit K.
    Chatterjee, Debashis
    Berner, Zsolt
    Bhattacharya, Prosun
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Role of competing ions on the mobilization of arsenic in groundwater of sedimentary aquifers: insight from surface complexation modelingManuscript (preprint) (Other academic)
  • 13.
    Biswas, Ashis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. University of Kalyani.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. Swedish University of Agricultural Sciences.
    Neidhardt, Harald
    Karlsruhe Institute of Technology, Germany.
    Halder, Dipti
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. University of Kalyani.
    Kundu, Amit Kumar
    University of Kalyani, India.
    Chatterjee, Debashis
    University of Kalyani, India.
    Berner, Zsolt
    Karlsruhe Institute of Technology, Germany.
    Bhattacharya, Prosun
    University of Kalyani.
    Estimating the role of competing ions on the arsenic mobilization processes in the aquifers of Bengal Basin by surface complexation modeling2013Conference paper (Refereed)
    Abstract [en]

    This study investigates the relative roles of the different competing ions on the arsenic (As) mobilization in the sedimentary aquifers of Bengal basin by surface complexation modeling of the temporal varaibility of As in shallow (<50 m) groundwater. Two sets of piezometers (2×5 = 10), installed at the two sites with relatively contrasting dissolved As concentration in groundwater, were monitored bi-weekly for As and other hydrogeochemical parameters over a period of 20 months. The estimation of the standard deviation (SD) for As(III) reflects strong temporal variation (SD ≥10 μg/L) in all the piezometers of two sites over the monitoring period. Particularly, the variation is more prominent in the shallowest part of the aquifer, where the site specific cyclic trends are evident. While, As(V) shows significant temporal variation in the piezometers of high As site only and no specific trend is reflected in the variation.

    Two different surface complexation models (SCMs), developed for ferrihydrite and goethite have been explored to account for the observed temporal variation in As(III) and As(V) concentrations. The SCM for ferrihydrite has provided the better estimation for both As(III) and As(V) variations.

    Among the different competing ions, PO43- appears as the major competitor of As(III) and As(V) adsorption onto ferrihydrite and the competition ability decreases in the order PO43- >> Fe(II) > H4SiO4 = HCO3-. It is further revealed that a small decrease in pH significantly increases the concentration of As(III) and decreases the As(V) concentration and vice versa. The present study suggests that the reductive dissolution of Fe oxyhydroxides alone cannot explain the observed high As concentration in groundwater of the sedimentary aquifers. Perhaps, the reductive dissolution of Fe oxyhydroxides followed by competitive sorption reactions with the aquifer sediment is the processes conducive for As enrichment in the groundwater of Bengal basin.

  • 14. Braun, S.
    et al.
    McLaren, T. I.
    Frossard, E.
    Tuyishime, J. R. M.
    Börjesson, G.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering. Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
    Phosphorus desorption and isotope exchange kinetics in agricultural soils2020In: Soil use and management, ISSN 0266-0032, E-ISSN 1475-2743Article in journal (Refereed)
    Abstract [en]

    To improve phosphorus (P) fertilization and environmental assessments, a better understanding of release kinetics of solid-phase P to soil solution is needed. In this study, Fe (hydr)oxide-coated filter papers (Fh papers), isotopic exchange kinetics (IEK) and chemical extractions were used to assess the sizes of fast and slowly desorbing P pools in the soils of six long-term Swedish field experiments. The P desorption data from the Fh-paper extraction of soil (20 days of continual P removal) were fitted with the Lookman two-compartment desorption model, which estimates the pools of fast (Q1) and slowly (Q2) desorbing P, and their desorption rates k1 and k2. The amounts of isotope-exchangeable P (E) were calculated (E1min to E&gt;3 months) and compared with Q1 and Q2. The strongest relationship was found between E1 min and Q1 (r2 =.87, p &lt;.01). There was also an inverse relationship between the IEK parameter n (the rate of exchange) and k1 (r2 =.52, p &lt;.01) and k2 (r2 =.52, p &lt;.01), suggesting that a soil with a high value of n desorbs less P per time unit. The relationships between these results show that they deliver similar information, but both methods are hard to implement in routine analysis. However, Olsen-extractable P was similar in magnitude to Q1 (P-Olsen = 1.1 × Q1 + 2.3, r2 =.96), n and k1 were related to P-Olsen/P-CaCl2, while k2 was related to P-oxalate/P-Olsen. Therefore, these extractions can be used to estimate the sizes and desorption rates of the different P pools, which could be important for assessments of plant availability and leaching.

  • 15.
    Braun, Sabina
    et al.
    Swedish University of Agricultural Sciences, Department of Soil and Environment.
    Warrinnier, Ruben
    KU Leuven, Belgium.
    Börjesson, Gunnar
    Swedish University of Agricultural Sciences, Department of Soil and Environment.
    Ulén, Barbro
    Swedish University of Agricultural Sciences, Department of Soil and Environment.
    Smolders, Erik
    KU Leuven, Belgium.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Assessing the ability of soil tests to estimate labile phosphorus in agricultural soils: Evidence from isotopic exchange2019In: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 337, p. 350-358Article in journal (Refereed)
    Abstract [en]

    Efficient phosphorus (P) fertilization strategies are essential for intensive crop production with minimal negative environmental impacts. A key factor in sustainable P use is assessment of the plant available soil P pool using soil P tests. This study determined isotopically exchangeable P after six days of reaction with 33PO4 (P-E (6 d)) to determine how accurately two commonly used P tests, Olsen and AL (acid ammonium acetate lactate) can quantify the amount of labile P. Soil samples were taken from both highly P-amended and unamended plots at six sites within the Swedish long-term soil fertility experiments. According to P K-edge XANES spectroscopy, the P speciation was dominated by Al-bound P and organic P, with additional contributions from Fe-bound P and Ca phosphates in most soils. The results showed that the AL test overestimated P-E (6 d) by a factor of 1.70 on average. In contrast, the Olsen test underestimated P-E (6 d), with the mean ratios of P-Olsen to P-E (6 d) being 0.52 for high-P and 0.19 for low-P soils. The 33P/31P ratio in the Olsen extract of a 33PO4 spiked soil was closer to that of a 0.005 mol L−1 CaCl2 soil extract than the corresponding ratio in the AL extract, suggesting that AL extraction solubilized more non-labile P. In conclusion, the AL and Olsen methods are not suitable for direct quantification of the isotopically exchangeable soil P pool after 6 days of equilibration. However, based on the results, Olsen may be superior to AL for classification of soil P status, due to its even performance for calcareous and non-calcareous soils and lower extraction of non-labile P.

  • 16. Campos Pereira, H.
    et al.
    Ullberg, M.
    Kleja, D. B.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. Swedish University of Agricultural Sciences, Sweden.
    Ahrens, L.
    Sorption of perfluoroalkyl substances (PFASs) to an organic soil horizon – Effect of cation composition and pH2018In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 207, p. 183-191Article in journal (Refereed)
    Abstract [en]

    Accurate prediction of the sorption of perfluoroalkyl substances (PFASs) in soils is essential for environmental risk assessment. We investigated the effect of solution pH and calculated soil organic matter (SOM) net charge on the sorption of 14 PFASs onto an organic soil as a function of pH and added concentrations of Al3+, Ca2+ and Na+. Often, the organic C-normalized partitioning coefficients (KOC) showed a negative relationship to both pH (Δlog KOC/ΔpH = −0.32 ± 0.11 log units) and the SOM bulk net negative charge (Δlog KOC = −1.41 ± 0.40 per log unit molc g−1). Moreover, perfluorosulfonic acids (PFSAs) sorbed more strongly than perfluorocarboxylic acids (PFCAs) and the PFAS sorption increased with increasing perfluorocarbon chain length with 0.60 and 0.83 log KOC units per CF2 moiety for C3–C10 PFCAs and C4, C6, and C8 PFSAs, respectively. The effects of cation treatment and SOM bulk net charge were evident for many PFASs with low to moderate sorption (C5–C8 PFCAs and C6 PFSA). However for the most strongly sorbing and most long-chained PFASs (C9–C11 and C13 PFCAs, C8 PFSA and perfluorooctane sulfonamide (FOSA)), smaller effects of cations were seen, and instead sorption was more strongly related to the pH value. This suggests that the most long-chained PFASs, similar to other hydrophobic organic compounds, are preferentially sorbed to the highly condensed domains of the humin fraction, while shorter-chained PFASs are bound to a larger extent to humic and fulvic acid, where cation effects are significant.

  • 17.
    Campos-Pereira, Hugo
    et al.
    Swedish Univ Agr Sci SLU, Dept Soil & Environm, SE-75007 Uppsala, Sweden..
    Kleja, Dan B.
    Swedish Univ Agr Sci SLU, Dept Soil & Environm, SE-75007 Uppsala, Sweden.;Swedish Geotech Inst SGI, SE-58193 Linköping, Sweden..
    Sjostedt, Carin
    Swedish Univ Agr Sci SLU, Dept Soil & Environm, SE-75007 Uppsala, Sweden..
    Ahrens, Lutz
    Swedish Univ Agr Sci SLU, Dept Aquat Sci & Assessment, SE-75007 Uppsala, Sweden..
    Klysubun, Wantana
    Synchrotron Light Res Inst, Nakhon Ratchasima 30000, Thailand..
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. Swedish Univ Agr Sci SLU, Dept Soil & Environm, SE-75007 Uppsala, Sweden..
    The Adsorption of Per- and Polyfluoroalkyl Substances (PFASs) onto Ferrihydrite Is Governed by Surface Charge2020In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 54, no 24, p. 15722-15730Article in journal (Refereed)
    Abstract [en]

    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.

  • 18.
    Elert, Mark
    et al.
    Kemakta Konsult AB, Box 12655, S-11293 Stockholm, Sweden..
    Kleja, Dan Berggren
    Swedish Univ Agr Sci, S-75007 Uppsala, Sweden..
    Eliaeson, Karin
    IVL Swedish Environm Res Inst, S-10031 Stockholm, Sweden..
    Gustafsson, Jon Petter
    KTH.
    Wadstein, Ebba
    Swedish Geotech Inst, S-58193 Linkoping, Sweden..
    Enell, Anja
    Swedish Geotech Inst, S-58193 Linkoping, Sweden..
    RELEASES FROM CONTAMINATED SITES - METHODS TO ASSESS LEACHING AND TRANSPORT2008In: CONSOIL 2008: THEME D - RISKS & IMPACTS, VOLS 1 AND 2, HELMHOLTZ CENTRE ENVIRONMENTAL RESEARCH-UFZ , 2008, p. 104-+Conference paper (Refereed)
  • 19. Envall, Ida
    et al.
    Fagerlund, Fritjof
    Westholm, Lena Johansson
    aberg, Charlotte
    Bring, Arvid
    Land, Magnus
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    What evidence exists related to soil retention of phosphorus from on-site wastewater treatment systems in boreal and temperate climate zones?: A systematic map protocol2020In: Environmental Evidence, E-ISSN 2047-2382, Vol. 9, no 1, article id 22Article in journal (Refereed)
    Abstract [en]

    Background Soil-based on-site wastewater treatment systems (OWSs) are suspected to contribute to eutrophication of surface waters, due to the discharge of phosphorus (P). However, along the flow path between the facilities and surface waters, different processes contribute to delay the transport of phosphorus through the ground. This may reduce the unwanted impact on receiving water bodies. However, the strength and significance of this so-called soil retention remains unclear. In Sweden, there are nearly one million OWSs. To protect surface waters, a high P removal rate (up to 90%) is often required by the local municipalities. However, since these requirements may have costly consequences to property owners, it is debated as to whether they are too strict. In this debate, it is often claimed that the retention of P occurring in natural environments may be underestimated by authorities. Accordingly, there is a need for a scrutiny of the available evidence related to soil retention of phosphorus from OWSs. This is the objective of the planned systematic map. Focus will be on boreal and temperate climate zones. Methods Searches will be made for peer-reviewed articles and grey literature using bibliographic databases, search engines, specialist websites and stakeholder contacts. The references will be screened for relevance according to a predefined set of eligibility criteria. At stage one, after testing and clarifying the eligibility criteria, the references will be single-screened based on title and abstract. At stage two, potentially relevant references will be screened in full-text independently by two reviewers. We will compile a detailed database of the relevant studies. Moreover, a narrative report will be produced, describing the research landscape in general terms. This will be carried out with a conceptual model, describing the processes involved in P retention in natural environments, as a foundation. It will be discussed where the respective studies/study types fit into the conceptual model, and also evaluated how each study/study type can be related to the overarching question of eutrophication. Moreover, we will describe identified knowledge gaps that warrant further primary research effort, as well as identified knowledge clusters that could be suitable for systematic reviews.

  • 20. Eriksson, Ann Kristin
    et al.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. Swedish University of Agricultural Sciences, Sweden.
    Hesterberg, Dean
    Phosphorus speciation of clay fractions from long-term fertility experiments in Sweden2015In: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 241, p. 68-74Article in journal (Refereed)
    Abstract [en]

    Phosphorus (P) losses from agricultural soils constitute a main driver for eutrophication of the Baltic Sea. There is limited knowledge about sorption and release processes of P in these soils, especially concerning the effects of fertilization. In this study, P speciation of the clay fractions from six different soils in long-term fertility experiments in Sweden was investigated by P K-edge XANES spectroscopy. As expected, unfertilized soils had lower concentrations of acid-digestible P compared with fertilized soils. Based on best-fit standards that emerged from linear combination fitting (LCF) of XANES spectra, phosphate sorbed on iron (Fe) (hydr)oxides was a dominant P species in clay fractions from unfertilized soils containing more than 35 mmol kg(-1) of oxalate-extractable Fe. In contrast, P sorbed on aluminum (Al) (hydr)oxides predominated in soils with lower concentrations of oxalate-extractable Fe. A greater proportion of organically bound P was fit for soil samples containing >2% organic carbon. The soils included one calcareous soil for which a greater proportion of P was fit as apatite. After long-term fertilization, P had accumulated mainly as P adsorbed to Al (hydr) oxides according to the XANES analysis. Our research shows that P speciation in fertilized agricultural soils depended on the level of P buildup and on the soil properties.

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  • 21. Eriksson, Ann Kristin
    et al.
    Hesterberg, Dean
    Klysubun, Wantana
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SLU, Sweden.
    Phosphorus dynamics in Swedish agricultural soils as influenced by fertilization and mineralogical properties: Insights gained from batch experiments and XANES spectroscopy2016In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 566, p. 1410-1419Article in journal (Refereed)
    Abstract [en]

    The soil chemistry of phosphorus (P) is important for understanding the processes governing plant availability as well as the risk of environmental losses of P. The objective of this research was to investigate both the speciation and the pH-dependent solubility patterns of P in clayey agricultural soils in relation to soil mineralogy and fertilization history. The study focused on soil samples from six fields that were subjected to different P fertilization regimes for periods of 45 to 57 years. Soil P speciation was analyzed by P K-edge XANES spectroscopy and chemical fractionation, sorption isotherms were constructed, and dissolved P was measured as a function of pH. The XANES fitting results showed that organic P and P adsorbed to Fe and Al (hydr) oxides were common P constituents in all soils. Calciumphosphateswere identified in five of six soil samples. The XANES results also indicated an increase in P adsorbed to Al and to a lesser extent Fe (hydr) oxides as a result of fertilization. Moreover, the fluorescence intensity from the P K-edge XANES analysis was most strongly correlated with HCl-digestible P (r = 0.81***). Consistent with the XANES analysis, laboratory sorption isotherm models showed that the Freundlich sorption coefficient (K-F) was most closely related to oxalate-extractable Al. Greater proportions of Ca phosphate in two of the heavily fertilized soils in combination with enhanced PO4 solubilization upon sample acidification indicated neoformation of Ca-phosphate precipitates. The results for the unfertilized soil samples generally showed a minimum in dissolved PO4 between pH 6.5 and 7.5, with increases particularly at lower pH. This behavior can be explained either by the dissolution of Al-hydroxide-type sorbents or Ca phosphates at lower pH. In fertilized soils, there was no consistent trend in pH-dependent solubilization of P, with a complex relationship to solid-phase speciation. To conclude, inorganic P species changed most dynamically in agricultural clay soils over a period of several decades, and the role of pH in the solubilization of P depended mainly on P fertilization history and the content of reactive Ca phosphates.

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  • 22. Eriksson, Ann Kristin
    et al.
    Hillier, Stephen
    Hesterberg, Dean
    Klysubun, Wantana
    Ulén, Barbro
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. Swedish University of Agricultural Sciences, Sweden.
    Evolution of phosphorus speciation with depth in an agricultural soil profile2016In: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 280, p. 29-37Article in journal (Refereed)
    Abstract [en]

    With time, different soil-forming processes such as weathering, plant growth, accumulation of organic matter, and cultivation are likely to affect phosphorus (P) speciation. In this study, the depth distribution of P species was investigated for an agricultural clay soil, Lanna, Sweden. Small amounts of apatite-P was demonstrated in the topsoil whereas the speciation of Pat 70-100 cm depth consisted of approximately 86% apatite according to P K-edge XANES (X-ray absorption near-edge structure) spectroscopy. Because there were only minor differences in bulk mineralogy and texture, these variations in P speciation were interpreted as the result of apatite weathering of the topsoil. Speciation modeling on soil extracts supported this idea: hydroxyapatite was not thermodynamically stable in the top 50 cm of the soil. Apatite was enriched in the bulk soil relative to the clay fraction, as expected during apatite dissolution. Combined results from batch experiments, XANES spectroscopy and X-ray diffraction suggested chemical transformations of the topsoil as a result from accumulation of organic matter and airing from tillage followed by enhanced weathering of apatite, amphiboles, clay minerals, and iron oxides. This caused the formation of poorly crystalline secondary iron and aluminum (hydr)oxides in the topsoil, which retained part of the released P from apatite. Other P was incorporated into organic forms. Furthermore, the results also showed that short-term acidification below the current pH value (below 5.5 in the topsoil and 7.2 in the deeper subsoil) caused significant solubilization of P. This is attributed to two different mechanisms: the instability of Al-containing sorbents (e.g. Al hydroxides) at low pH (in the topsoil), and the acid-mediated dissolution of apatite (the subsoil).

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  • 23.
    Eveborn, David
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology. KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. JTI - Swedish Institute of Agricultural and Environmental Engineering, Sweden .
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology. KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. Department of Soil and Environment, Swedish University of Agricultural Sciences, Sweden.
    Elmefors, Elin
    JTI,Swedish Institute of Agricultural and Environmental Engineering.
    Yu, Lin
    Center for Environmental and Climate Research (CEC), Lund University.
    Eriksson, Ann-Kristin
    Department of Soil and Environment, Swedish University of Agricultural Sciences.
    Ljung, Emelie
    JTI,Swedish Institute of Agricultural and Environmental Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Phosphorus in soil treatment systems: accumulation and mobility2014In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 64, p. 42-52Article in journal (Refereed)
    Abstract [en]

    In several western countries, septic tanks with subsequent soil treatment systems (STS) are a common treatment technique for domestic wastewater in rural areas. However the suitability of STS (especially relatively close to surface waters) can be questioned since the discharge of phosphorus (P) from such effluents is not well known. In this study, six STS in Sweden (11 to 28 years old) were investigated by means of batch and column experiments on samples taken from the unsaturated subsoil beneath the distribution pipes. At all sites the wastewater had clearly influenced the soil. This was observed through decreased pH, increased amounts of oxalate extractable metals and altered P sorption properties. The amount of accumulated P in the STS (defined as the amount of total P in the STS samples minus the amount of total P in unused soil samples) were found to be between 0.32 and 0.87 kg m-3, which in most cases was just a small fraction of the estimated P load (< 30%). Column studies revealed that remarkably high P concentrations (up to 6 mg L-1) were leached from the material when deionized water was applied. However, the response to deionized water varied between the sites. The affinity for P in the soils was well correlated to the amount of oxalate-extractable aluminium (as evidenced by a strong relationship between oxalate-extractable Al and oxalate-extractable P) and generally soils with high content of oxalate extractable Al was also less vulnerable to P leakage.

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    Eveborn et al 2014 AAM
  • 24.
    Eveborn, David
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Hesterberg, Dean
    University Raleigh, Department of Soil Science, North Carolina, USA.
    Hillier, Stephen
    Macaulay Institute, Craigiebuckler, Aberdeen, UK.
    XANES Speciation of P in Environmental Samples: An Assessment of Filter Media for on-Site Wastewater Treatment2009In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, no 17, p. 6515-6521Article in journal (Refereed)
    Abstract [en]

    X-ray absorption near edge structure (XANES) spectroscopyis a useful technique for characterization of chemical speciesof phosphorus in complex environmental samples. To developand evaluate bed filters as sustainable on-site wastewater treatment solutions, our objective in this study was to determine the chemical forms of accumulated phosphorus in a selectionof promising filter materials: Filtralite P, Filtra P, Polonite, Absol, blast furnace slag, and wollastonite. Full-scale operational wastewater-treatment systems were sampled and in addition, filter samples collected from laboratory studies provided access to additional media and complementary samples.Phosphorus species were characterized using phosphorus K-edge XANES spectroscopy, complemented by X-ray powder diffraction (XRPD) and attenuated total reflectance Fouriertransform infrared spectroscopy (ATR-FTIR). No systematic differences could be seen in the results between laboratory and full-scale samples. All six filter media contained significant amounts of crystalline calcium phosphates. Some samples also contained amorphous calcium phosphate (>60 % of totalP in Absol). In Filtralite P and blast furnace slag, more than 35 % of the accumulated phosphorus was associated with Fe or Al. Both the power and shortcomings of XANES analysis for characterizing P species in these filter media are discussed.

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  • 25.
    Eveborn, David
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Kong, Deguo
    Department of Applied Environmental Science, Stockholm University, Sweden.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Wastewater treatment by soil infiltration: Long-term phosphorus removal2012In: Journal of Contaminant Hydrology, ISSN 0169-7722, E-ISSN 1873-6009, Vol. 140, p. 24-33Article in journal (Refereed)
    Abstract [en]

    Phosphorus (P) leaching from on-site wastewater treatment systems may contribute to eutrophication. In developed countries the most common on-site treatment technique is septic systems with soil infiltration. However, the current knowledge about long term P removal in soil treatment systems is not well developed and the data used for estimation of P losses from such systems are unreliable. In this study we sampled four filter beds from community-scale soil treatment systems with an age of between 14 and 22 years to determine the long-term P removal and to investigate the chemical mechanisms behind the observed removal. For one site the long-term P removal was calculated using a mass balance approach. After analysis of the accumulated P. it was estimated that on average 12% of the long-term P load had been removed by the bed material. This indicates a low overall capacity of soil treatment systems to remove phosphorus. Batch experiments and chemical speciation modelling indicated that calcium phosphate precipitation was not an important long-term P removal mechanism, with the possible exception of one of the sites. More likely, the P removal was induced by AlPO4 precipitation and/or sorption to poorly ordered aluminium compounds, as evidenced by strong relationships between oxalate-extractable Al and P.

  • 26.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Arsenate adsorption to soils: Modelling the competition from humic substances2006In: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 136, no 02-jan, p. 320-330Article in journal (Refereed)
    Abstract [en]

    There is currently no agreement to what extent humic substances may compete with arsenate and other anions for oxide adsorption sites in soils, and how to model this interaction. In this study, batch experiments were made in which the competition between fulvic acid and arsenate was studied in a spodic Bs horizon. Additional experiments were performed in which the pH and concentration dependence of arsenate adsorption was studied in four soils. The results showed that fulvic acid decreased the adsorption of AsO4, probably because of competition effects. The K-d value of AsO4 adsorption to the four studied soils differed by three orders of magnitude at pH 5. The introduction of an irreversibly sorbed component RO- into the Three-Plane CD-MUSIC model, and the optimisation of RO- using the K-d of AsO4 for one sample from each data set, permitted the use of the model to predict AsO4 adsorption under different conditions. On the whole, the predictions were reasonably close to measured values, but the model failed in 3 of 4 soils at high surface coverage. A strong relationship between the optimised RO- value and the observed pyrophosphate-extractable C value supported the assumption that RO- can be considered as being an adsorbed humic functional group. The large concentrations of RO- compared to those of adsorbed PO4 and SO4 suggest that humic substances may be the most important competitors for anion adsorption sites in many soils.

  • 27.
    Gustafsson, Jon Petter
    KTH, Superseded Departments (pre-2005), Land and Water Resources Engineering.
    Modeling the acid-base properties and metal complexation of humic substances with the Stockholm Humic Model2001In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 244, no 1, p. 102-112Article in journal (Refereed)
    Abstract [en]

    To describe the binding of protons and metals to humic substances, the Stockholm Humic Model (SHM) has been developed. The model employs a discrete-site approach similar to that of Model V/VI, although it has another electrostatic submodel, based on the Basic Stern concept. An empirical set of equations has been introduced to account for the extra screening of charge inside the gel-like structures of the humic substances. Six adjustable parameters are needed to describe proton binding to humic or fulvic acids. To simulate metal binding, equilibrium constants are defined for mono- and bidentate coordination and an extra parameter, Delta LK2, accounts for binding-site heterogeneity. It is shown that the SHM appears to be able to describe proton binding well; the quality of the fits is similar to those obtained by Model V/VI and the NICA-Donnan model. The SHM was capable of correctly describing metal binding and competitive interactions over a wide range of conditions, although the model performance was not very convincing concerning the ionic strength dependence of metal binding and stepwise proton-metal exchange stoichiometries.

  • 28.
    Gustafsson, Jon Petter
    KTH, Superseded Departments (pre-2005), Land and Water Resources Engineering.
    Modelling competitive anion adsorption on oxide minerals and an allophane-containing soil2001In: European Journal of Soil Science, ISSN 1351-0754, E-ISSN 1365-2389, Vol. 52, no 4, p. 639-653Article in journal (Refereed)
    Abstract [en]

    Can surface complexation constants for anions, drawn from the literature for reference oxides, be combined to describe competitive adsorption in a spodic B horizon sample containing the important adsorbent minerals proto-imogolite allophane and ferrihydrite? To answer this and to derive complexation constants for the corresponding reference oxides, a CD-MUSIC model was used, with arsenate as the sorbing ion. To minimize the interference from competing organic substances, a sample containing little organic matter was used. To describe the adsorption of added arsenate correctly, it was found that competitive interactions from sulphate, silicic acid and phosphate had to be considered. In the model, the specific surface area of singly coordinated AlOH groups of allophane, the sulphate surface complexation constant on allophane, and the total concentration of reactive silicic acid were fitted. All other parameters were fixed using reference oxide values. The results indicated that arsenate, phosphate and silicic acid formed stronger surface complexes on ferrihydrite than on gibbsite or allophane, whereas the reverse was true for sulphate. I conclude that the approach used should provide significant qualitative information on the competitive adsorptive interactions in soils. However, the approach may be impractical for routine simulations and predictions. This is partly due to the uncertainty of the assumption that the properties of allophane and ferrihydrite in real soils can be approximated by those of gibbsite and ferrihydrite synthesized in the laboratory. Another difficulty is that the adsorption of arsenate and phosphate might not reach equilibrium within the limited time of most experiments.

  • 29.
    Gustafsson, Jon Petter
    KTH, Superseded Departments (pre-2005), Land and Water Resources Engineering.
    Modelling molybdate and tungstate adsorption to ferrihydrite2003In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 200, no 02-jan, p. 105-115Article in journal (Refereed)
    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.

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  • 30.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Soil chemical behaviour of cadmium pigments from paints2013Report (Other academic)
    Abstract [en]

    A review focusing on the thermodynamic stability and dissolution rates of Cd-containing sulphides and selenides from paints is presented. In the surface horizon of Swedish agricultural soils, cadmium sulphide, CdS(s), and cadmium selenide, CdSe(s), are shown to be thermodynamically unstable. The presence of electron acceptors such as oxygen gas and iron(III) will lead to gradual dissolution of these compounds. The dissolution rate of Cd-containing sulphides is dependent on the amount of crystalline zinc sulphide in contact with the cadmium, as zinc will be dissolved preferentially from a mixed cadmium zinc sulphide mineral. In the absence of crystalline zinc sulphide, Cd will be dissolved completely after 1-3 years. The presence of crystalline zinc sulphide can extend the life span of CdS to 1-2 decades; however, sewage sludge contains mostly amorphous ZnS that will dissolve more quickly. In conclusion, if a time frame of several decades is applied, it is very likely that Cd from Cd pigments has a similar solubility and bioavailability as an easily soluble Cd salt such as cadmium chloride.

  • 31.
    Gustafsson, Jon Petter
    KTH, Superseded Departments (pre-2005), Land and Water Resources Engineering.
    The surface chemistry of imogolite2001In: Clays and clay minerals, ISSN 0009-8604, E-ISSN 1552-8367, Vol. 49, no 1, p. 73-80Article in journal (Refereed)
    Abstract [en]

    Imogolite is a tubular aluminosilicate which is common in Andosols and Spodosols. The high pH at point-of-zero charge at the outer parts of the tube and the anomalously high chloride adsorption of imogolite suggested that there may be structural charge associated with this mineral. The structural charge may arise because of changes in bond valence imposed by the incorporation of orthosilicate anions in a gibbsite-type sheet. By using a Basic Stem Model approach, it is shown that the surface charge properties of imogolite are explained if the mean Al-O bond valence of the outer -Al2OH groups is higher than the inner -Al2OHSiO3 groups. Hence, a weak positive charge is developed on the outer tube walls whereas a negative charge develops in the tubular pores. The best model fits were obtained where either one or two units of structural charge per unit cell of tube were assumed. The model may also explain why imogolite tubes are normally aggregated in large bundles in close hexagonal packing, because bound counterions may hold the tubes together. However, to arrive at good model descriptions, the deprotonation of -Al2OH groups must occur at a higher pH than that expected when assuming that all surface oxygens form two hydrogen bridges with H2O. A more precise structure of imogolite is required to test fully this hypothesis.

  • 32.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. Swedish Univ Agr Sci, Dept Soil & Environm, Box 7014, S-75007 Uppsala, Sweden.
    Vanadium geochemistry in the biogeosphere -speciation, solid-solution interactions, and ecotoxicity2019In: APPLIED GEOCHEMISTRY, Vol. 102, p. 1-25Article, review/survey (Refereed)
    Abstract [en]

    Vanadium is a metal that receives increasing attention due to its possible toxicity and its increased use in society, i.e. in high-grade steel and in vanadium redox-flow batteries. Already today, the global biogeochemical cycle of vanadium is heavily impacted by human activities, and these impacts will probably increase. The total V concentration in the upper part of the Earth's crust, and in soils, is near 100 mg V kg(-1). Usually, the dissolved V concentration is low. In seawater the mean dissolved V concentration is 1.8 mu g L-1, and in freshwaters the concentration is commonly below 1 mu g L-1 although in areas with volcanic and sedimentary rocks it may be much higher, i.e. at the slopes of Mt. Etna, Italy, concentrations of up to 180 mu g V L-1 have been recorded. Vanadium is a redox-sensitive element, which occurs in three oxidation states (+III, +IV and +V) in the environment. Whereas vanadium(V) usually occurs as the oxyanion vanadate(V) under most environmental conditions, vanadyl(IV) is an oxocation that is stable at low pH and/or mildly reducing conditions, particularly when the organic matter concentration is high. Vanadium(III), which is the least studied form of vanadium, occurs under strongly reducing conditions. All vanadium forms are strongly bound to environmental sorbents: vanadate(V) is bound as a bidentate complex to iron, aluminium, and titanium (hydr)oxides, and with a stronger affinity than that of orthophosphate (o-phosphate). Vanadyl(IV) is strongly complexed to natural organic matter, while vanadium(III) may substitute for other trivalent ions in mineral structures. Despite this, vanadium may be mobilized to the aqueous phase, for example under high-pH conditions. Studies with V K-edge XANES spectroscopy have shown that most oxic soils usually contain a mixture of vanadium(IV) that is octahedrally coordinated in primary minerals, and surface-bound vanadate(V) on iron and aluminium (hydr) oxides, although acid organic soils are dominated by organically complexed vanadyl(IV). In reduced environments, such as in sediments and black shales, available evidence suggests that the V consists of a mixture of organically complexed vanadyl(IV) and unknown vanadium(III) species. However, considerable uncertainty exists on the V speciation under reducing conditions, and additional research is recommended. Vanadium is essential for some species of cyanolichens and algae due to its presence in vanadium nitrogenase, which can be important for N fixation in boreal ecosystems, and in vanadium haloperoxidases, which mediate the oxidation of halides, particularly iodine and bromine. In certain organisms vanadium is accumulated for unknown reasons, e.g. in ascidians, where V accumulates as a vanadium(III) complex with organic S, and in Amanita mushrooms, in which amavadin, a stable vanadium(IV)-organic complex, is accumulated. However, at high concentrations vanadium is toxic to many organisms. This is mostly due to its interference with o-phosphate in a number of biomolecules. Available evidence shows that toxic effects appear in the mg V L-1 range for most studied species. However, some organisms, i.e. algae and possibly some soil bacteria, are more sensitive. In soils, the toxic response is related to the soil solution V concentration, rather than to the solid-phase concentration. The o-phosphate concentration has been identified as a parameter that influences toxicity, but the relationship between the P status and the environmental risk of V toxicity is not yet well determined - as a result risk-based guidelines remain uncertain. There is urgent need for more research on this topic. Vanadium, being a redox-sensitive element, responds to sudden environmental change such as flooding that leads to decreased redox potential. In most, but not all, cases, an increased solubilisation of vanadium is observed after flooding, which can be attributed to reductive dissolution of vanadate(V)-sorbing iron (hydr)oxides and to vanadate(V) reduction to vanadyl(IV) that forms stable complexes with dissolved organic matter. The vanadium redox conversions are carried out by a large number of genera of bacteria. Bioremediation methods are being developed that may reduce vanadate(V) to vanadyl(IV), which may reduce the bioavailability of vanadium in many soils.

  • 33.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. Swedish University of Agricultural Sciences, Sweden.
    Akram, Muhammad
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Tiberg, Charlotta
    Predicting sulphate adsorption/desorption in forest soils: Evaluation of an extended Freundlich equation2015In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 119, p. 83-89Article in journal (Refereed)
    Abstract [en]

    Sulphate adsorption and desorption can delay the response in soil acidity against changes in acid input. Here we evaluate the use of an extended Freundlich equation for predictions of pH-dependent SO4 adsorption and desorption in low-ionic strength soil systems. Five B horizons from Spodosols were subjected to batch equilibrations at low ionic strength at different pHs and dissolved SO4 concentrations. The proton coadsorption stoichiometry (eta), i.e. the number of H+ ions co-adsorbed for every adsorbed SO42- ion, was close to 2 in four of five soils. This enabled the use of a Freundlich equation that involved only two adjustable parameters (the Freundlich coefficient K-F and the non-ideality parameter m). With this model a satisfactory fit was obtained when only two data points were used for calibration. The root-mean square errors of log adsorbed SO4 ranged from 0.006 to 0.052. The model improves the possibility to consider SO4 adsorption/desorption processes correctly in dynamic soil chemistry models.

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  • 34.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. Swedish Univ Agr Sci, Dept Soil & Environm, POB 7014, S-75007 Uppsala, Sweden..
    Belyazid, Salim
    Stockholm Univ, Dept Phys Geog, S-10691 Stockholm, Sweden..
    McGivney, Eric
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Löfgren, Stefan
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, POB 7050, S-75007 Uppsala, Sweden..
    Aluminium and base cation chemistry in dynamic acidification models - need for a reappraisal?2018In: SOIL, ISSN 2199-3971, Vol. 4, no 4, p. 237-250Article in journal (Refereed)
    Abstract [en]

    Long-term simulations of the water composition in acid forest soils require that accurate descriptions of aluminium and base cation chemistry are used. Both weathering rates and soil nutrient availability depend on the concentrations of Al3+, of H+, and of base cations (Ca2+, Mg2+, Na+, and K+). Assessments of the acidification status and base cation availability will depend on the model being used. Here we review in what ways different dynamic soil chemistry models describe the processes governing aluminium and base cation concentrations in the soil water. Furthermore, scenario simulations with the HD-MINTEQ model are used to illustrate the difference between model approaches. The results show that all investigated models provide the same type of response to changes in input water chemistry. Still, for base cations we show that the differences in the magnitude of the response may be considerable depending on whether a cation-exchange equation (Gaines-Thomas, Gapon) or an organic complexation model is used. The former approach, which is used in many currently used models (e.g. MAGIC, ForSAFE), causes stronger pH buffering over a relatively narrow pH range, as compared to state-of-the-art models relying on more advanced descriptions in which organic complexation is important (CHUM, HD-MIN PLQ). As for aluminium, a "fixed" gibbsite constant, as used in MAGIC, SMART/VSD, and ForSAFE, leads to slightly more pH buffering than in the more advanced models that consider both organic complexation and Al(OH)(3) (s) precipitation, but in this case the effect is small. We conclude that the descriptions of acid-base chemistry and base cation binding in models such as MAGIC, SMART/VSD, and ForSAFE are only likely to work satisfactorily in a narrow pH range. If the pH varies greatly over time, the use of modern organic complexation models is preferred over cation-exchange equations.

  • 35.
    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)
  • 36.
    Gustafsson, Jon Petter
    et al.
    KTH, Superseded Departments (pre-2005), Land and Water Resources Engineering.
    Berggren, D.
    Simonsson, M.
    Zysset, M.
    Mulder, J.
    Aluminium solubility mechanisms in moderately acid Bs horizons of podzolized soils2001In: European Journal of Soil Science, ISSN 1351-0754, E-ISSN 1365-2389, Vol. 52, no 4, p. 655-665Article in journal (Refereed)
    Abstract [en]

    The processes controlling the retention and release of aluminium in acid forest soils are still subject to controversy, and therefore a universal hypothesis as to what mechanisms are operating has not been firmly established. By studying the Bs horizons of Swedish and Swiss podzolized soils, and by analysing data in the literature, we have found that aluminium hydroxide, and in some cases also poorly ordered imogolite, may control Al solubility in moderately acid (pH>4.2-4.3) Bs horizons. The strongest evidence in support of the presence of a quickly reacting Al(OH)(3) pool came from the temperature dependence of Al solubility in a Bs horizon, which was consistent with the reaction enthalpy of an Al(OH)3 phase such as gibbsite, and from the observation that the eon activity product for Al(OH)3 was the same regardless of whether equilibrium was reached from over- or undersaturation. The pool of Al(OH)3 is commonly small and may be completely dissolved after large additions of acid. This may be explained by the continuing redissolution of reactive Al(OH)(3) to form less soluble imogolite-type phases. By using the same methods it was found that soil suspensions did not reach equilibrium with poorly ordered imogolite even after 17 days. Thus, imogolite probably does not control Al solubility in the short term in many soils despite the common occurrence of this mineral. This is due to the relatively slow kinetics of imogolite formation and dissolution, especially at low temperatures and at small solution H4SiO4 concentrations.

  • 37.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Bhattacharya, Prosun
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Geochemical modelling of arsenic adsorption to oxide surfaces2007In: Arsenic in soil and groundwater environment: Biogeochemical Interactions, Health Effects and Remediation / [ed] Bhattacharya, P., Mukherjee, A.B., Bundschuh, J., Zevenhoven, R., Loeppert, R.H., Elsevier, 2007, p. 159-206Chapter in book (Refereed)
    Abstract [en]

    In natural environments, arsenic chemistry is dominated by the reactions of its two predominant soluble forms, arsenate and arsenite. To predict the fate of As in the environment, it is necessary to consider processes that act to restrict its mobility. The mobility of As is strongly influenced by adsorption reactions to particle surfaces. Arsenate and arsenite may form surface complexes with a number of different oxides, including Fe-, Al-, Mn- and Ti oxides. The focus of this chapter is on the adsorption of As(III) and As(V) to the surfaces of oxides, in particular Fe oxides. We have analysed the existing data for arsenite and arsenate adsorption to ferrihydrite and goethite. Spectroscopic results show that arsenate forms bidentate binuclear complexes under all conditions; for arsenite, evidence has been found both for a bidentate binuclear complex and for a weaker outer-sphere complex, which may be of some importance at low ionic strength. We optimized As adsorption parameters for two surface complexation models, the diffuse double-layer model (DLM) and the three-plane CD-MUSIC model (TPCD), taking into account the spectroscopic evidence. For arsenate adsorption to ferrihydrite, the new DLM constants imply stronger binding than the previous compilation by Dzombak and Morel (1990), whereas for arsenite the revised DLM constants are in reasonable agreement. The surface complexation models could not be optimized satisfactorily for data sets in which the dissolved arsenite concentration at equilibrium was larger than 10 mM; the reasons for this are discussed. Simulations of competition effects show that o-phosphate competes strongly with arsenate over the whole pH range. Silicic acid and carbonate are important competitors in the circumneutral pH range, while sulphate may have a small competitive effect at low pH. Humic substances are important competitors when a large part of the Fe oxides is covered with humic substances. By contrast, calcium promotes arsenate adsorption at alkaline pH because of surface charge effects.

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  • 38.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Braun, Sabina
    Tuyishime, J. R. Marius
    Adediran, Gbotemi A.
    Warrinnier, Ruben
    Hesterberg, Dean
    A Probabilistic Approach to Phosphorus Speciation of Soils Using P K-edge XANES Spectroscopy with Linear Combination Fitting2020In: Soil systems, ISSN 2571-8789, Vol. 4, no 2, article id 26Article in journal (Refereed)
    Abstract [en]

    A common technique to quantitatively estimate P speciation in soil samples is to apply linear combination fitting (LCF) to normalized P K-edge X-ray absorption near-edge structure (XANES) spectra. Despite the rapid growth of such applications, the uncertainties of the fitted weights are still poorly known. Further, there are few reports to what extent the LCF standards represent unique end-members. Here, the co-variance between 34 standards was determined and their significance for LCF was discussed. We present a probabilistic approach for refining the calculation of LCF weights based on Latin hypercube sampling of normalized XANES spectra, where the contributions of energy calibration and normalization to fit uncertainty were considered. Many of the LCF standards, particularly within the same standard groups, were strongly correlated. This supports an approach in which the LCF standards are grouped. Moreover, adsorbed phytates and monetite were well described by other standards, which puts into question their use as end-members in LCF. Use of the probabilistic method resulted in uncertainties ranging from 2 to 11 percentage units. Uncertainties in the calibrated energy were important for the LCF weights, particularly for organic P, which changed with up to 2.7 percentage units per 0.01 eV error in energy. These results highlight the necessity of careful energy calibration and the use of frequent calibration checks. The probabilistic approach, in which at least 100 spectral variants are analyzed, improves our ability to identify the most likely P compounds present in a soil sample, and a procedure for this is suggested in the paper.

  • 39.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Dässman, Ellinor
    Swedish University of Agricultural Sciences.
    Bäckström, Mattias
    Örebro University.
    Towards a consistent geochemical model for prediction of uranium(VI) removal from groundwater by ferrihydrite2009In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 24, no 3, p. 454-462Article in journal (Refereed)
    Abstract [en]

    Uranium(VI), which is often elevated in granitoidic groundwaters, is known to adsorb strongly to Fe (hydr)oxides under certain conditions. This process can be used in water treatment to remove U(VI). To develop a consistent geochemical model for U(VI) adsorption to ferrihydrite, batch experiments were performed and previous data sets reviewed to optimize a set of surface complexation constants using the 3-plane CD-MUSIC model. To consider the effect of dissolved organic matter (DOM) on U(VI) speciation, new parameters for the Stockholm Humic Model (SHM) were optimized using previously published data. The model, which was constrained from available X-ray absorption fine structure (EXAFS) spectroscopy evidence, fitted the data well when the surface sites were divided into low- and high-affinity binding sites. Application of the model concept to other published data sets revealed differences in the reactivity of different ferrihydrites towards U(VI). Use of the optimized SHM parameters for U(VI)-DOM complexation showed that this process is important for U(VI) speciation at low pH. However in neutral to alkaline waters with substantial carbonate present, Ca-U-CO3 complexes predominate. The calibrated geochemical model was used to simulate U(VI) adsorption to ferrihydrite for a hypothetical groundwater in the presence of several competitive ions. The results showed that U(VI) adsorption was strong between pH 5 and 8. Also near the calcite saturation limit, where U(VI) adsorption was weakest according to the model, the adsorption percentage was predicted to be >80%. Hence U(VI) adsorption to ferrihydrite-containing sorbents may be used as a method to bring down U(VI) concentrations to acceptable levels in groundwater.

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  • 40.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Kleja, D. B.
    Modeling salt-dependent proton binding by organic soils with the MICA-Donnan and Stockholm Humic models2005In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 39, no 14, p. 5372-5377Article in journal (Refereed)
    Abstract [en]

    Models are available for simulations of proton dissociation and cation binding by natural organic matter; two examples are the NICA-Donnan and Stockholm Humic (SHM) models. To model proton and metal binding, it is necessary to properly account for the ionic strength dependence of proton dissociation. In previous applications of the models for soils it was assumed that the electrostatic interactions for solid-phase humic substances were the same as in solution;this assumption was recently challenged. Therefore, we reanalyzed previously published acid-base titrations of acid-washed Sphagnum peat, and we produced additional data sets for two Sphagnum peats and two Spodosol Oe horizons. For the soil suspensions, the original NICA-Donnan and SHM models, which were developed for dissolved humic substances, underestimated the observed salt dependence considerably. When a fixed Donnan volume of 1 L kg(-1) for humic substances in the solid phase was used, the NICA-Donnan model fits were much improved. Also for SHM, slight changes produced improved model fits. The models also produced acceptable simulations of the dissolved Ca, Mg, and Cd concentrations, provided that cation selectivity was introduced. In conclusion, the proposed extensions to the NICA-Donnan and SHM models were shown to predict the salt dependence of solid-phase humic substances more satisfactorily than earlier model versions.

  • 41.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Lumsdon, David G.
    James Hutton Institute, Aberdeen, UK.
    Comment on "Citrate adsorption can decrease soluble phosphate concentration in soils: Results of theoretical modelling'' by Marek Duputel, Nicolas Devau, Michel Brossard, Benoit Jaillard, Davey L. Jones, Philippe Hinsinger and Frederic Gerard (2013)2014In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 46, p. 85-89Article in journal (Refereed)
    Abstract [en]

    By use of a multi-site surface complexation model, Duputel et al. (2013) showed that citrate can decrease the solubility of phosphorus in soils, in contrast to what is commonly expected. We have identified several major errors in their model, which put the conclusions in doubt. We argue that major re-evaluation of their modelling approach is needed.

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  • 42.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Mwamila, Luhuvilo B.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Kergoat, Kevin
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    The pH dependence of phosphate sorption and desorption in Swedish agricultural soils2012In: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 189, p. 304-311Article in journal (Refereed)
    Abstract [en]

    A number of previous studies have reported the existence of a minimum in phosphate solubility between pH 5.5 and 7 in non-calcareous soils. Different hypotheses have been forwarded to explain this phenomenon. In this study, ten soil samples with varying textures and phosphorus status were subjected to batch experiments in which dissolved phosphate was measured as a function of pH and phosphate load. Soil samples with more than 20% clay all had a minimum phosphate solubility between pH 6 and 7, whereas for samples with <10% clay, no such minimum was observed. Further experiments involving additions of phosphate and arsenate showed an increasing adsorption of these anions with decreasing pH also below pH 6 in clay soils, suggesting that the pH dependence on adsorption and desorption in short-term experiments was not the same. Kinetic experiments showed that the increased phosphate desorption at lower pH values in non-calcareous clay soils was a quick process, which is consistent with adsorption/desorption being the most important mechanism governing the retention and release of inorganic P. Moreover, by comparing extraction results with batch experiment results for samples from a long-term fertility experiment, it was concluded that more than 60% of the accumulated phosphate was occluded, i.e. not reactive within 6 days. Additional evidence for an important role of occluded phosphate comes from an analysis of the Freundlich sorption isotherms for the studied soils. It is hypothesized that interlayered hydroxy-Al and hydroxy-Fe polymers in clay minerals may be important for P dynamics in clay soils by trapping some of the P in an occluded form. The results also suggest that improved knowledge on the speciation and dynamics of phosphorus in soils is required for consistent mechanistically based modeling of phosphate sorption/desorption reactions.

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  • 43.
    Gustafsson, Jon Petter
    et al.
    Swedish University of Agricultural Sciences, Uppsala.
    Oromieh, Aidin Geranmayeh
    Swedish University of Agricultural Sciences, Uppsala.
    Sjöstedt, Carin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Persson, Ingmar
    Sveriges Lantbruksuniversitet.
    Berggren Kleja, Dan
    Swedish Geotechnical Institute, Stockholm, Sweden.
    Chromium (III) and bismuth (III) complexation to organic matter: EXAFS Spectroscopy and equilibrium modeling2013In: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 77, no 5, p. 1235-Article in journal (Refereed)
    Abstract [en]

    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 Cr

    K-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.

  • 44.
    Gustafsson, Jon Petter
    et al.
    KTH, Superseded Departments (pre-2005), Land and Water Resources Engineering.
    Pechova, P.
    Berggren, D.
    Modeling metal binding to soils: The role of natural organic matter2003In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 37, no 12, p. 2767-2774Article in journal (Refereed)
    Abstract [en]

    The use of mechanistically based models to simulate the solution concentrations of heavy metals in soils is complicated by the presence of different sorbents that may bind metals. In this study, the binding of Zn, Pb, Cu, and Cd by 14 different Swedish soil samples was investigated. For 10 of the soils, it was found that the Stockholm Humic Model (SHM) was able to describe the acid-base characteristics, when using the concentrations of active humic substances and Al as fitting parameters. Two additional soils could be modeled when ion exchange to clay was also considered, using a component additivity approach. For dissolved Zn, Cd, Ca, and Mg reasonable model fits were produced when the metal-humic complexation parameters were identical for the 12 soils modeled. However, poor fits were obtained for Pb and Cu in Aquept B horizons. In two of the soil suspensions, the Lund A and Romfartuna Bhs, the calculated speciation agreed well with results obtained by using cation-exchange membranes. The results suggest that organic matter is an important sorbent for metals in many surface horizons of soils in temperate and boreal climates, and the necessity of properly accounting for the competition from Al in simulations of dissolved metal concentrations is stressed.

  • 45.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Persson, I.
    Oromieh, A. G.
    Van Schaik, J. W. J.
    Sjöstedt, Carin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Kleja, D. B.
    Chromium(III) complexation to natural organic matter: Mechanisms and modeling2014In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 48, no 3, p. 1753-1761Article in journal (Refereed)
    Abstract [en]

    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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  • 46.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Persson, Ingmar
    Kleja, Dan Berggren
    Van Schaik, Joris W. J.
    Binding of iron(III) to organic soils: EXAFS spectroscopy and chemical equilibrium modeling2007In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 41, no 4, p. 1232-1237Article in journal (Refereed)
    Abstract [en]

    The complexation of iron(III) to soil organic matter is important for the binding of trace metals in natural environments because of competition effects. In this study, we used extended X-ray absorption fine structure (EXAFS) spectroscopy to characterize the binding mode for iron(III) in two soil samples from organic mor layers, one of which was also treated with iron(III). In most cases the EXAFS spectra had three significant contributions, inner-core Fe-O/N interactions at about 2.02(2) A, Fe-C interactions in the second scattering shell at 3.00(4) A, and a mean Fe-Fe distance at 3.37(3) A. One untreated sample showed features typical for iron (hydr)oxides; however, after treatment of iron(III) the EXAFS spectrum was dominated by organically complexed iron. The presence of a Fe-Fe distance in all samples showed that the major part of the organically complexed iron was hydrolyzed, most likely in a mixture of complexes with an inner core of (O5Fe)(2)O and (O5Fe)(3)O. These results were used to constrain a model for metal-humic complexation, the Stockholm Humic Model (SHM). The model was able to describe iron(III) binding very well at low pH considering only one dimeric iron(III)-humic complex. The competition effect on trace metals was also well described.

  • 47.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Renman, Agnieszka
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Poll, Katarina
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Phosphate removal by mineral-based sorbents used in filters for small-scale wastewater treatment2008In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 42, no 1-2, p. 189-197Article in journal (Refereed)
    Abstract [en]

    The mineral-based sorbents Filtra P, Polonite (R), natural wollastonite and water-cooled blast furnace slag (WCBFS) were studied in terms of their PO4 removal performance. Results from a long-term column experiment showed that both Filtra P and Polonite (R) removed > 95% of PO4 from the applied synthetic solution, and that the used filter materials had accumulated several (1.9-19) g kg(-1) P. Phosphorus was removed also by natural wollastonite and WCBFS, but these materials were less efficient. Batch experiments on the used materials showed that the solubility PO4 was considerably larger than the one expected for crystalline Ca phosphates such as hydroxyapatite, and results from investigations with attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) on the Filtra P material showed that the formed P phase was not crystalline. These evidence suggest that a soluble amorphous tricalcium phosphate (ATCP) was formed in the mineral-based sorbents; the apparent solubility constant on dissolution was estimated to log K-s = -27.94 ( 0.31) at 21 degrees C. However, since only up to 18% of the accumulated PO4 was readily dissolved in the experiments, it cannot be excluded that part of the phosphorus had crystallized to slightly less soluble phases. In conclusion, Filtra P and Polonite are two promising mineral-based sorbents for phosphorus removal, and at least part of the accumulated phosphorus is present in a soluble form, readily available to plants.

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  • 48.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Tiberg, Charlotta
    SLU.
    Fosfors betydelse för metallers mobilitet i mark2013Report (Other academic)
    Abstract [en]

    The aim with this project was to investigate the role of dissolved phosphate for the adsorption of lead(II), copper(II), cadmium(II) and uranium(VI) onto ferrihydrite and to soils. The methods involved batch studies, EXAFS spectroscopy, and equilibrium modelling. Phosphate was found to significantly enhance the adsorption of all investigated metals onto ferrihydrite. Results obtained so far show that the results are consistent with the formation of ternary surface complexes at low pH, but additional research is required to understand the processes in more detail. Similar enhancements were not observed in soil samples to which phosphate is added, and the reasons for this remain to be fully elucidated. In any case, this research shows that the presence of phosphate may restrict the mobility of many trace metals in environments that contain iron(III) (hydr)oxides.

  • 49.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Tiberg, Charlotta
    Molybdenum binding to soil constituents in acid soils: An XAS and modelling study2015In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 417, p. 279-288Article in journal (Refereed)
    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.

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  • 50.
    Gustafsson, Jon Petter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Tiberg, Charlotta
    Swedish University of Agricultural Sciences.
    Edkymish, Abubaker
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Kleja, Dan Berggren
    Swedish Geotechnical Institute.
    Modelling lead(II) sorption to ferrihydrite and soil organic matter2011In: Environmental Chemistry, ISSN 1448-2517, E-ISSN 1449-8979, Vol. 8, no 5, p. 485-492Article in journal (Refereed)
    Abstract [en]

    Lead(II) adsorption to soil organic matter and iron (hydr)oxides is strong, and may control the geochemical behaviour of this metal. Here, we report the adsorption of Pb(2+) (i) to 2-line ferrihydrite, and (ii) to a mor layer. The results showed that ferrihydrite has heterogeneous Pb(2+) binding. Use of a surface complexation model indicated that similar to 1% of the surface sites adsorbed Pb(2+) more strongly than the remaining 99 %. Although only one surface complexation reaction was used (a bidentate complex of the composition (equivalent to FeOH)(2)Pb(+)), three classes of sites with different affinity for Pb(2+) were needed to simulate Pb(2+) binding correctly over all Pb/Fe ratios analysed. For the mor layer, Pb(2+) sorption was much stronger than current models for organic complexation suggest. The results could be described by the Stockholm Humic Model when the binding heterogeneity was increased, and when it was assumed that 0.2% of the binding sites were specific for Pb. Use of revised model parameters for nine Vietnamese soils suggest that lead(II) binding was more correctly simulated than before. Thus, underestimation of lead(II) sorption to both (hydr) oxide surfaces and organic matter may explain the failure of previous geochemical modelling attempts for lead(II).

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