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  • 1. Aeppli, Christoph
    et al.
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Holmstrand, Henry
    Gustafsson, Örjan
    Use of Cl and C Isotopic Fractionation to Identify Degradation and Sources of Polychlorinated Phenols: Mechanistic Study and Field Application2013In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 47, no 2, p. 790-797Article in journal (Refereed)
    Abstract [en]

    The widespread use of chlorinated phenols (CPs) as a wood preservative has led to numerous contaminated sawmill sites. However, it remains challenging to assess the extent of in situ degradation of CPs. We evaluated the use of compound-specific chlorine and carbon isotope analysis (Cl- and C-CSIA) to assess CP biotransformation. In a laboratory system, we measured isotopic fractionation during oxidative 2,4,6-trichlorophenol dechlorination by representative soil enzymes (C. fumago chloroperoxidase, horseradish peroxidase, and laccase from T. versicolor). Using a mathematical model, the validity of the Rayleigh approach to evaluate apparent kinetic isotope effects (AKIE) was confirmed. A small but significant Cl-AKIE of 1.0022 ± 0.0006 was observed for all three enzymes, consistent with a reaction pathway via a cationic radical species. For carbon, a slight inverse isotope effect was observed (C-AKIE = 0.9945 ± 0.0019). This fractionation behavior is clearly distinguishable from reported reductive dechlorination mechanisms. Based on these results we then assessed degradation and apportioned different types of technical CP mixtures used at two former sawmill sites. To our knowledge, this is the first study that makes use of two-element CSIA to study sources and transformation of CPs in the environment.

  • 2.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Eriksson, Erik J.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Palm, Fredrik
    Umeå University, Faculty of Arts, Humlab.
    SEAD - The Strategic Environmental Archaeology Database: Progress Report Spring 20142014Report (Other academic)
    Abstract [en]

    This report provides an overview of the progress and results of the VR:KFI infrastructure projects 2007-7494 and (825-)2010-5976. It should be considered as a status report in an on-going long-term research infrastructure development project.

    Download full text (pdf)
    SEAD - Progress Report Spring 2014
  • 3. Colla, Christopher A.
    et al.
    Casey, William H.
    Ohlin, C. André
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Computational prediction of Mg-isotope fractionation between aqueous [Mg(OH2)6]2+ and brucite2018In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 227, p. 64-74Article in journal (Refereed)
    Abstract [en]

    The fractionation factor in the magnesium-isotope fractionation between aqueous solutions of magnesium and brucite changes sign with increasing temperature, as uncovered by recent experiments. To understand this behavior, the Reduced Partition Function Ratios and isotopic fractionation factors (Δ26/24Mgbrucite-Mg(aq)) are calculated using molecular models of aqueous [Mg(OH2)6]2+ and the mineral brucite at increasing levels of density functional theory. The calculations were carried out on the [Mg(OH2)6]2+·12H2O cluster, along with different Pauling-bond-strength-conserving models of the mineral lattice of brucite. Three conclusions were reached: (i) all levels of theory overestimate 〈Mg‒O〉 bond distances in the aqua ion complex relative to Tutton’s salts; (ii) the calculations predict that brucite at 298.15 K is always enriched in the heavy isotope, in contrast with experimental observations; (iii) the temperature dependencies of Wimpenny et al. (2014) and Li et al. (2014) could only be achieved by fixing the 〈Mg‒O〉 bond distances in the [Mg(OH2)6]2+·12H2O cluster to values close to those observed in crystals that trap the hydrated ion.

  • 4.
    Ekeberg, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. ABB Schweiz AG, Corporate Research, CH-5405 Baden-Dättwil, Switzerland.
    Stasiewicz, Kristof
    Swedish Institute of Space Physics, P.O. Box 537, SE-751 21 Uppsala, Sweden.
    Wannberg, Gudmund
    Swedish Institute of Space Physics, P.O. Box 812, SE-981 28 Kiruna, Sweden.
    Sergienko, Tima
    Swedish Institute of Space Physics, P.O. Box 812, SE-981 28 Kiruna, Sweden.
    Eliasson, Lars
    Swedish Institute of Space Physics, P.O. Box 812, SE-981 28 Kiruna, Sweden.
    Incoherent scatter ion line enhancements and auroral arc-induced Kelvin-Helmholtz turbulence2015In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 122, p. 119-128Article in journal (Refereed)
    Abstract [en]

    We present two cases of incoherent-scatter ion line enhancements in conjunction with auroral arcs drifting through the radar beam. The up- and downshifted ion line shoulders as well as the spectral region between them are enhanced equally and simultaneously. The power enhancements are one order of magnitude above the thermal level and are concentrated in less than 15 km wide altitude ranges at the ionospheric F region peak. The auroral arc passages are preceded by significantly enhanced ion temperatures in the E region, which are shown to generate high velocity shears. We use a Hall MHD model of velocity shears perpendicular to the geomagnetic field and show that a Kelvin-Helmholtz instability will grow for the two presented cases. We assess the possibility that the subsequently generated low frequency turbulence can explain the observed spectrally uniform ion line power enhancements.

  • 5.
    Fahlman, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    En geokemisk kartering över området kring Nasa silvergruva: Effekterna av historisk gruvdrift i svensk fjällmiljö2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of the study was to map the extent of Fe, Cu, Pb, As, Zn and S contamination in the area surrounding the Nasa silver mine. The mine operated between 1635 and 1810 with some prospecting performed in 1889, and has become infamous for the gruesome ways that the indigenous people were treated during the early years of operation. This study tested three hypotheses through a geochemical survey: 1) sulfide oxidation is still active in the abandoned mine, 2) the soil downslope of the mine is contaminated by mine drainage, and 3) the stream downslope of the mine is affected in the same way. All three hypotheses were valid, as the results showed that still, >200 years after mining operations ceased, signs of the historical mining are clearly visible in the surrounding environment. Acidic conditions were discovered in surface waters close to the waste rock piles, which indicates active sulfide oxidation. In addition, elevated levels of Fe, Cu, Pb, As, Zn and S were found in both soil and stream sediment downslope of the mines, as compared to reference localities upstream the mine (p <0.05). These results suggest that previous assessments of the mine being no threat to the environment may not be entirely correct. This study illustrates how mining waste can continue to affect the local, sub-arctic environment long after mining operations have ceased.

    Download full text (pdf)
    En geokemisk kartering över området kring Nasa silvergruva
  • 6. Galli, André
    et al.
    Wurz, Peter
    Kallio, Esa
    Ekenbäck, Andreas
    Institutet för rymdfysik (IRF).
    Holmström, Mats
    Institutet för rymdfysik, Kiruna.
    Barabash, Stas
    Institutet för rymdfysik, Kiruna.
    Gregoriev, Alexander
    Futaana, Yoshifumi
    Institutet för rymdfysik, Kiruna.
    Fok, Mei-Ching
    Gunell, H
    The tailward flow of energetic neutral atoms observed at Mars2008In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 113, article id E12012Article in journal (Refereed)
    Abstract [en]

    The ASPERA-3 experiment on Mars Express provides the first measurements of energetic neutral atoms (ENAs) from Mars. These measurements are used to study the global structure of the interaction of the solar wind with the Martian atmosphere. In this study we describe the tailward ENA flow observed at the nightside of Mars. After characterizing energy spectra of hydrogen ENA signals, we present composite images of the ENA intensities and compare them to theoretical predictions (empirical and MHD models). We find that the tailward flow of hydrogen ENAs is mainly generated by shocked solar wind protons. Despite intensive search, no oxygen ENAs above the instrument threshold are detected. The results challenge existing plasma models and constrain the hydrogen exospheric densities and atmospheric hydrogen and oxygen loss rates at low solar activity.

  • 7.
    Hagvall, Kristoffer
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Persson, Per
    Karlsson, Torbjörn
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Effects of natural organic matter on gibbsite dissolutionManuscript (preprint) (Other academic)
  • 8.
    Hagvall, Kristoffer
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Persson, Per
    Karlsson, Torbjörn
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Speciation of aluminum in soils and stream waters: The importance of organic matter2015In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 417, p. 32-43Article in journal (Refereed)
    Abstract [en]

    Aluminum (Al) is the most common metal in the Earth's crust, and exists mainly in the form of silicates, oxides and hydroxides, or in complexes with natural organic matter (NOM) or inorganic ligands. Since speciation is a key factor for understanding the environmental impact of Al, it is important to determine the chemical forms of Al that predominate in different natural media and under varying geochemical conditions. This study investigated how complexation with NOM influenced the speciation of Al(III) in different environmental samples (isolated aquatic NOM, organic soils and stream waters) using X-ray absorption spectroscopy (XAS) and Infrared (IR) spectroscopy. The combined spectroscopic results showed that Al(III) formed mononuclear complexes with carboxylic functional groups in NOM that were sufficiently stable to suppress the hydrolysis and polymerization of Al(III). These organic Al complexes were favored at slightly acidic pH values between pH 3 and 6 and at decreasing Al concentrations. The XAS results of the organic soils and the stream water samples indicated a variation in the speciation from a predominance of organically complexed Al in the stream waters to a mixture of Al-NOM complexes and precipitated Al phases (Al hydroxides and/or Al silicates) in the organic soils. Although the presented XAS results were limited by relatively low signal-to-noise caused by the low K-edge energy of Al, the combined spectroscopic results provided new and useful information about Al in different environmental samples and showed that NOM and pH are important parameters controlling the speciation of Al.

  • 9. Hahn, A.
    et al.
    Rosen, Peter
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Kliem, P.
    Ohlendorf, C.
    Zolitschka, B.
    Comparative study of infrared techniques for fast biogeochemical sediment analyses2011In: Geochemistry Geophysics Geosystems, ISSN 1525-2027, E-ISSN 1525-2027, Vol. 12, p. Q10003-Article in journal (Refereed)
    Abstract [en]

    Analysis of sediment samples in the visible to mid infrared (IR) region requires small amounts of sample material and enables rapid and cost efficient geochemical analysis of mineral and organic sediment components. Here we use geochemical properties (total organic and inorganic carbon, biogenic silica, total nitrogen) from the ICDP deep drilling project PASADO to compare three different IR spectroscopy techniques: Diffuse Reflectance Fourier Transform IR Spectrometry (DRIFTS), Attenuated Total Reflectance Fourier Transform IR Spectroscopy (ATR-FTIRS) and Visible Near IR Spectroscopy (VNIRS). ATR-FTIRS and VNIRS are more rapid techniques compared to DRIFTS. Results show that calibration models developed using DRIFTS are most robust (correlation coefficient: R = 0.92 for TIC, R = 0.84 for BSi, R = 0.97 for TOC, R = 0.95 for TN). However, good statistical performance was also obtained by using ATR-FTIRS and VNIRS. When time and costs are limiting factors, these tools may be given preference for rapid biogeochemical screening.

  • 10.
    Hansson, Sophia V.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Kaste, James M.
    College of William & Mary.
    Chen, Keyao
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bindler, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Beryllium-7 as a natural tracer for short-term downwash in peat2014In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 119, no 1-3, p. 329-339Article in journal (Refereed)
    Abstract [en]

    Several factors can affect the integrity of natural archives such as peat records, e.g., decomposition and nutrient cycling, and it has also been hypothesized that some rapid downward transport of atmospherically derived elements may occur. We test this hypothesis by analyzing the short-lived, natural tracer beryllium-7 (tA1/2A = 53.4 days) in five cores from two peatlands. In triplicate hummock cores from a raised bog in southern Sweden, Be-7 could be measured to 20, 18 and 8 cm depth, and in a nutrient-poor mire in northern Sweden to a depth of 16 cm in a Sphagnum lawn core, but only 4 cm in the dominant, more-decomposed fen peat, indicating some spatial variability both within and between sites. Total Be-7 inventories were 320-450 Bq m(-2) in the bog, and 150 Bq m(-2) (lawn) and 240 Bq m(-2) (fen peat) in the mire. 25-79 % of the total inventory of Be-7 was located in the upper 2-cm layer. To further test downwashing, in the laboratory we applied a CuBr-solution to two cores and a Cu-solution to one core taken from the mire Sphagnum lawn, all with low water table conditions. About 50 % of the added Cu and similar to 35 % of the added Br were retained in the surface (2 cm) layer; 1-3 % of the Cu was found at 8-12 cm depth and similar to 1 % of the Br was measured in the lowest level (20-22 cm). Based on our novel approach using Be-7 and experimental work we show that short-term downwashing can occur in peatlands and we suggest the depth of this will depend on the properties of the peat, e.g., bulk density and decomposition, as well as hydrology.

  • 11.
    Hansson, Sophia V.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Kaste, James M.
    College of William & Mary.
    Olid, Carolina
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bindler, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Incorporation of radiometric tracers in peat and implications for estimating accumulation rates2014In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 493, p. 170-177Article in journal (Refereed)
    Abstract [en]

    Accurate dating of peat accumulation is essential for quantitatively reconstructing past changes in atmospheric metal deposition and carbon burial. By analyzing fallout radionuclides Pb-210, Cs-137, Am-241, and Be-7, and total Pb and Hg in 5 cores from two Swedish peatlands we addressed the consequence of estimating accumulation rates due to downwashing of atmospherically supplied elements within peat. The detection of Be-7 down to 18-20 cm for some cores, and the broad vertical distribution of Am-241 without a well-defined peak, suggest some downward transport by percolating rainwater and smearing of atmospherically deposited elements in the uppermost peat layers. Application of the CRS age-depth model leads to unrealistic peat mass accumulation rates (400-600 g m(-2) yr(-1)), and inaccurate estimates of past Pb and Hg deposition rates and trends, based on comparisons to deposition monitoring data (forest moss biomonitoring and wet deposition). After applying a newly proposed IP-CRS model that assumes a potential downward transport of Pb-210 through the uppermost peat layers, recent peat accumulation rates (200-300 g m(-2) yr(-1)) comparable to published values were obtained. Furthermore, the rates and temporal trends in Pb and Hg accumulation correspond more closely to monitoring data, although some off-set is still evident. We suggest that downwashing can be successfully traced using Be-7, and if this information is incorporated into age-depth models, better calibration of peat records with monitoring data and better quantitative estimates of peat accumulation and past deposition are possible, although more work is needed to characterize how downwashing may vary between seasons or years.

  • 12.
    Hansson, Sophia V.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rydberg, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Kylander, Malin
    Gallagher, Kerry
    Bindler, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Evaluating paleoproxies for peat decomposition and their relationship to peat geochemistry2013In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 23, no 12, p. 1666-1667Article in journal (Refereed)
    Abstract [en]

    The past decade has seen a rapid increase in interest in the biogeochemical record preserved in peat, particularly as it relates to carbon dynamics and environmental change. Importantly, recent studies show that carbon dynamics, that is, organic matter decomposition, can influence the record of atmospherically derived elements such as halogens and mercury. Most commonly, bulk density, light transmission, or carbon/nitrogen (C/N) ratios are used as a proxy to qualitatively infer the degree of decomposition in peat, but do these three proxies reflect the same patterns? Furthermore, how do each of these proxies relate to other geochemical data? To address these questions, we analyzed bulk density, light transmission, and C/N ratios, as well as multielement geochemistry (wavelength-dispersive x-ray fluorescence (WD-XRF)), in three hummock cores (70 cm in length, c. 500 years) from an ombrotrophic Swedish bog. To compare the proxies, we applied principal component analysis (PCA) to identify how the proxies relate to and interact with the geochemical matrix. This was coupled with changepoint modeling to identify and compare statistically significant changes for each proxy. Our results show differences between the proxies within and between cores, indicating each responds to a different part of the decomposition process. This is supported by the PCA, where the three proxies fall on different principal components. Changepoint analysis also showed that the inferred number of changepoints and their depths vary for each proxy and core. This suggests that decomposition is not fully captured by any one of these commonly used proxies, and thus, more than one proxy should be included.

  • 13.
    Hansson, Sophia V.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Tolu, Julie
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bindler, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Testing the downwash of atmospherically deposited metals in peat and the influence of rainfall intensityArticle in journal (Refereed)
  • 14. Jiang, Tao
    et al.
    Skyllberg, Ulf
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Green, Nelson W.
    Tang, Jianhui
    Wang, Dingyong
    Gao, Jie
    Li, Chuxian
    Characteristics of dissolved organic matter (DOM) and relationship with dissolved mercury in Xiaoqing River-Laizhou Bay estuary, Bohai Sea, China2017In: Environmental Pollution, ISSN 0269-7491, E-ISSN 1873-6424, Vol. 223, p. 19-30Article in journal (Refereed)
    Abstract [en]

    Abstract Because of heterogeneous properties, dissolved organic matter (DOM) is known to control the environmental fate of a variety of organic pollutants and trace metals in aquatic systems. Here we report absorptive and fluorescence properties of DOM, in concurrence with concentrations of dissolved mercury (Hg), along the Xiaoqing River-Laizhou Bay estuary system located in the Bohai Sea of China. A mixing model consisting of the two end-members terrestrial and aquatic DOM demonstrated that terrestrial signatures decreased significantly from the river into the estuary. Quasi-conservative mixing behavior of DOM sources suggests that the variations in the average DOM composition were governed by physical processes (e.g., dilution) rather than by new production and/or degradation processes. In contrast to some previous studies of river-estuary systems, the Xiaoqing River-Laizhou Bay estuary system displayed a non-significant correlation between DOM and Hg quantities. Based on this and the variation of Hg concentration along the salinity gradient, we concluded that Hg showed a non-conservative mixing behavior of suggested end-member sources. Thus, rather than mixing, Hg concentration variations seemed to be controlled by biogeochemical processes.

  • 15.
    Jonsson, Sofi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Skyllberg, Ulf
    Nilsson, Mats B.
    Lundberg, Erik
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Differentiated availability of geochemical mercury pools controls methylmercury levels in estuarine sediment and biota2014In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, p. 4624-Article in journal (Refereed)
    Abstract [en]

    Neurotoxic methylmercury (MeHg) formed from inorganic divalent mercury (HgII) accumulates in aquatic biota and remains at high levels worldwide. It is poorly understood to what extent different geochemical Hg pools contribute to these levels. Here we report quantitative data on MeHg formation and bioaccumulation, in mesocosm water-sediment model ecosystems, using five HgII and MeHg isotope tracers simulating recent Hg inputs to the water phase and Hg stored in sediment as bound to natural organic matter or as metacinnabar. Calculations for an estuarine ecosystem suggest that the chemical speciation of HgII solid/adsorbed phases control the sediment Hg pool's contribution to MeHg, but that input of MeHg from terrestrial and atmospheric sources bioaccumulates to a substantially greater extent than MeHg formed in situ in sediment. Our findings emphasize the importance of MeHg loadings from catchment runoff to MeHg content in estuarine biota and we suggest that this contribution has been underestimated.

  • 16.
    Jönsson, Jörgen
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Persson, Per
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lövgren, Lars
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Schwertmannite precipitated from acid mine drainage: phase transformation, sulphate release and surface properties2005In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 20, no 1, p. 179-191Article in journal (Refereed)
    Abstract [en]

    Schwertmannite precipitated from acid mine drainage at the Kristineberg Zn-Cu mine in northern Sweden has been characterised regarding elemental composition, phase transformation as a function of pH and time. SO42- release and speciation of SO42- associated with the solid. The elemental analysis gave the composition FeSOS(OH)(5.02)(-SO4)(1.49) . 0.5H(2)O where approximately 1/3 of the SO42- is adsorbed to the surface. The conversion of schwertmannite to goethite at pH 9 was complete within 187 days; at pH 6. the conversion was still incomplete after 514 days. Lower pH and relatively high SO42- concentration decreased the conversion even further. Also temperature was shown to be an important parameter for this process and low temperature (+4 degreesC) effectively stopped the transformation at pH 3. The release of SO42- was linear with pH and X-ray photoelectron spectroscopy measurements confirming that the surface bound SO42- was released before bulk SO42-. Zeta potential measurements indicate a pH(IEP) of 7.2 for the schwertmannite sample. Prior to conversion into goethite, the SO42- associated with schwertmannite was indicated by attenuated total reflectance FTIR spectroscopy to be present both as bulk and surface species. Furthermore: the speciation of surface SO42- was shown to vary with pH and two predominating species were detected. As pH increases. SO42- is increasingly Coordinated in an outer sphere mode whereas a stronger. possibly inner sphere, complex dominates. at low pH.

  • 17.
    Kanbar, Hussein Jaafar
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Applied Plant Biotechnology Laboratory (APBL), Faculty of Sciences, Department of Earth and Life Sciences, The Lebanese University, Hadat, Lebanon; Research and Analysis Platform for Environmental Sciences (PRASE), Doctoral School of Sciences and Technology (EDST), Faculty of Sciences, The Lebanese University, Hadat, Lebanon.
    Kaouk, Malak
    Mineral and chemical changes of sediments after Cu sorption and then desorption induced by synthetic root exudate2019In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 236, article id 124393Article in journal (Refereed)
    Abstract [en]

    Understanding the fate of anthropogenically introduced copper in sediments is important to comprehend the biogeochemical processes; consequently, beneficial utilization of Cu-rich materials can be proposed (e.g. soil amendment). Therefore, we address the behavior of copper and other metals at the liquid-solid interface of different grain sizes in lake sediments. Initially, the sediment fractions were characterized for mineralogy (XRD), chemical structure (FTIR), physicochemical parameters (mainly pH, cation exchange capacity, and electric conductivity), organic content, and chemical composition (AAS). Then, solutions of varying Cu concentrations were added to the fractions; the Cu concentrations of the sorption experiment were chosen according to the exchangeable cations of each fraction. A desorption experiment by synthetic root exudate was followed. The physicochemical parameters, functional groups, and mineralogy were noted before and after the two experiments. The sorption and desorption of Cu, Ca, Mg, K, and Na were also studied. The sediment fractions had similar mineralogy and chemical structure, yet the physicochemical composition and metal contents were different. The Cu sorption experiment showed that surface Ca and embedded Mg were the main cations that were exchanged with Cu, as shown by linear and logarithmic trends, respectively. The copper-sediment interaction mainly occurred at the organic interface. Finally, synthetic root exudate was able to restore part of the initial chemical structure of the sediments, indicating exchangeable Cu sorption on the organic part of the sediments. The various grain sizes had an insignificant influence on the behavior of metal sorption and desorption.

  • 18. Kang, Mingliang
    et al.
    Bardelli, Fabrizio
    Charlet, Laurent
    Géhin, Antoine
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Chen, Fanrong
    Morel, Marie-Christine
    Ma, Bin
    Liu, Chunli
    Redox reaction of aqueous selenite with As-rich pyrite from Jiguanshanore mine (China): reaction products and pathway2014In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 47, p. 130-140Article in journal (Refereed)
    Abstract [en]

    The interaction of an As-rich natural pyrite (FeS2.08As0.043) with aqueous Se(IV) was investigated as a function of pH, ferrous iron concentration, and reaction time. Arsenic is often the most abundant minor constituent of natural pyrite, and is believed to substitute for S in the pyrite structure. EXAFS measurements confirmed the presence of AsS dianion group, with arsenic in the same local configuration as in the arsenopyrite. Speciation studies indicated that Se(0) was the unique reduction product in the pH range 5.05–8.65 over a reaction period of &gt;1 month, while trace amounts of FeSeO3 might be formed at pH ⩟ 6.10. At pH &gt; 6.07, the formation of Fe(III)-(oxyhydr)oxide is kinetically favored, and it consumed nearly all the aqueous iron, including the extra added Fe2+, thereby inhibiting the formation of the thermodynamically most stable product: FeSe2. After oxidation by Se(IV), the occurrence of surface S0, significant aqueous sulfur deficit, and excessive leaching of arsenic in solution, indicate the preferential release of As impurity via arsenopyrite oxidation. The data suggest that the polysulfide-elemental sulfur pathway, which prevails in acid-soluble metal sulfides, is an important pathway in the oxidation of As-rich pyrite, in addition to the thiosulfate pathway for acid-insoluble pyrite. Control experiments on As-free natural pyrite further support this mechanism. This study confirms the potential of reductive precipitation to attenuate the mobility of Se in the environment and demonstrates that minor elements commonly present in natural pyrite can play a significant role on its dissolution pathway.

  • 19.
    Karlsson, Jon
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rydberg, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Segerström, Ulf
    Nordström, Eva-Maria
    Thöle, Philine
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Biester, Harald
    Bindler, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Tracing a bog-iron bloomery furnace in an adjacent lake-sediment record in Ängersjö, central Sweden, using pollen and geochemical signals2016In: Vegetation History and Archaeobotany, ISSN 0939-6314, E-ISSN 1617-6278, Vol. 25, no 6, p. 569-581Article in journal (Refereed)
    Abstract [en]

    Recent studies of bloomery sites in Sweden indicate the amount of iron produced with this early low-technology smelter was greater than previously thought, which implies greater economic importance. Little is known about the history of bloomery technology, not least the timeframe over which individual bloomeries were operated, as well as their impact on the landscape because of resource consumption and pollution. In this study we performed pollen and geochemical analyses of the lake-sediment record from Rortjarnen, which is 120 m from the remains of a documented bloomery [one radiocarbon date: ad 1300-1435 (1 sigma)], in A"ngersjo, Halsingland. A surface-soil transect shows a limited geochemical signal only within 20 m of the bloomery, and the sediment pollen record provides little direct evidence of an active bloomery and is consistent with other studied sites in the area linked to forest grazing or cultivation. Instead, we find major changes in sediment geochemistry during ad 800-1200, centered on a unique peak in Pb at ad 1030-1060. These changes include, e.g., Si (biogenic) and P, together with changes in pollen (e.g., Betula, Picea, Cyperaceae), which together indicate disturbance in the forest and especially the adjoining fen. We attribute these changes to a period of bloomery-related activities predating the radiocarbon date of the charcoal from the bloomery, and suggest that date represents a late phase for the site.

  • 20.
    Karlsson, Torbjörn
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hagvall, Kristoffer
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Persson, Per
    Adsorption of gallium(III)-organic matter complexes on gibbsite particlesManuscript (preprint) (Other academic)
  • 21.
    Klaminder, Jonatan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bindler, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Renberg, Ingemar
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    The biogeochemistry of atmospherically derived Pb in the boreal forest of Sweden2008In: Applied Geochemistry, Vol. 23, no 10, p. 2922-2931Article in journal (Refereed)
    Abstract [en]

    The use of stable Pb isotopes for tracing Pb contamination within the environment has strongly increased our understanding of the fate of airborne Ph contaminants within the boreal forest. This paper presents new stable Pb isotope (Pb-206/Pb-207 ratio) measurements of solid soil samples, stream water (from a mire outlet and a stream draining a forest dominated catchment) and components of Picea abies (roots, needles and stemwood), and synthesizes some of the authors' recent findings regarding the biogeochemistry of Ph within the boreal forest. The data clearly indicate that the biogeochemical cycling of Pb in the present-day boreal forest ecosystem is dominated by pollution Pb from atmospheric deposition. The Pb-206/Pb-207 ratios of the mor layer (O-horizon), forest plants and stream water (mainly between 1.14 and 1.20) are similar to atmospheric Pb pollution (1.14-1.19), while the local geogenic Pb of the mineral soil (C-horizon) has high ratios (>1.30). Roots and basal stemwood of the analyzed forest trees have higher Pb-206/Pb-207 ratios (1.15-1.30) than needles and apical stemwood (1.14-1.18), which indicate that the latter components are more dominated by pollution derived Pb. The low Pb-206/Pb-207 ratios of the mor layer suggest that the upward transport of Ph as a result of plant uptake is small (<0.04 mg m(-2) a(-1)) in comparison to atmospheric inputs (similar to 0.5 mg m(-2) a(-1)) and annual losses with percolating soil-water (similar to 2 mg m(-2) a(-1)); consequently, the Ph levels in the mor layer are now decreasing while the pool of Pb in the mineral soil is increasing. Streams draining mires appear more strongly affected by pollution Ph than streams from forested catchments, as indicated by Pb concentrations about three times higher and lower Pb-206/Pb-207 ratios (1.16 +/- 0.01 in comparison to 1.18 +/- 0.02). To what extent stream water Pb levels will respond to the build-up of Ph in deeper mineral soil layers remains uncertain. (c) 2008 Elsevier Ltd. All rights reserved.

  • 22. Kronberg, Rose-Marie
    et al.
    Schaefer, Jeffra K.
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Skyllberg, Ulf
    Mechanisms of Methyl Mercury Net Degradation in Alder Swamps: The Role of Methanogens and Abiotic Processes2018In: Environmental Science and Technology Letters, E-ISSN 2328-8930, Vol. 5, no 4, p. 220-225Article in journal (Refereed)
    Abstract [en]

    Wetlands are common net producers of the neurotoxin monomethylmercury (MeHg) and are largely responsible for MeHg bioaccumulation in aquatic food-webs. However, not all wetlands net produce MeHg; notable exceptions are black alder (Alnus glutinosa) swamps, which net degrade MeHg. Here we report the mechanisms of MeHg demethylation in one such swamp (EHT), shown to be a sink for MeHg during four consecutive years. The potential demethylation rate constant (k(d) ) in soil incubations was similar to 3 times higher in the downstream (EHT-D: k(d) similar to 0.14 d(-1)) as compared to the upstream part of the swamp (EHT-U: k(d) 0.05 d(-1)). This difference concurred with increased stream and soil pH, and a change in plant community composition. Electron acceptor and inhibitor addition experiments revealed that abiotic demethylation dominated at EHT-U while an additional and equally large contribution from biotic degradation was observed at EHT-D, explaining the increase in MeHg degradation. Biotic demethylation (EHT-D) was primarily due to methanogens, inferred by a decrease in k(d) to autoclaved levels following selective inhibition of methanogens. Though methanogen-specific transcripts (mcrA) were found throughout the wetland, transcripts clustering with Methanosaetaceae were exclusive to EHT-D, suggesting a possible role for these acetoclastic methanogens in the degradation of MeHg.

  • 23. Kylander, Malin E.
    et al.
    Martinez-Cortizas, Antonio
    Bindler, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Greenwood, Sarah L.
    Mörth, Carl-Magnus
    Rauch, Sebastien
    Potentials and problems of building detailed dust records using peat archives: An example from Store Mosse (the "Great Bog"), Sweden2016In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 190, p. 156-174Article in journal (Refereed)
    Abstract [en]

    Mineral dust deposition is a process often overlooked in northern mid-latitudes, despite its potential effects on ecosystems. These areas are often peat-rich, providing ample material for the reconstruction of past changes in atmospheric deposition. The highly organic (up to 99% in some cases) matrix of atmospherically fed mires, however, makes studying the actual dust particles (grain size, mineralogy) challenging. Here we explore some of the potentials and problems of using geochemical data from conservative, lithogenic elements (Al, Ga, Rb, Sc, Y, Zr, Th, Ti and REE) to build detailed dust records by using an example from the 8900-yr peat sequence from Store Mosse (the "Great Bog"), which is the largest mire complex in the boreo-nemoral region of southern Sweden. The four dust events recorded at this site were elementally distinct, suggesting different dominant mineral hosts. The oldest and longest event (6385-5300 cal yr BP) sees a clear signal of clay input but with increasing contributions of mica, feldspar and middle-REE- rich phosphate minerals over time. These clays are likely transported from a long-distance source (< 100 km). While dust deposition was reduced during the second event (5300-4370 cal yr BP), this is the most distinct in terms of its source character with [Eu/Eu*] UCC revealing the input of plagioclase feldspar from a local source, possibly active during this stormier period. The third (2380- 2200 cal yr BP) and fourth (1275-1080 cal yr BP) events are much shorter in duration and the presence of clays and heavy minerals is inferred. Elemental mass accumulation rates reflect these changes in mineralogy where the relative importance of the four dust events varies by element. The broad changes in major mineral hosts, grain size, source location and approximated net dust deposition rates observed in the earlier dust events of longer duration agree well with paleoclimatic changes observed in northern Europe. The two most recent dust events are much shorter in duration, which in combination with evidence of their local and regional character, may explain why they have not been seen elsewhere. 

  • 24.
    Lidman, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Radionuclide transport in the boreal landscape: Uranium, thorium and other metals in forests, wetlands and streams2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The boreal landscape is complex mosaic of vast forests, lakes and wetlands. Through the landscape flows a fine network of streams and rivers, carrying dissolved and suspended material from atmospheric deposition and weathering of soils and bedrock to downstream recipients. This thesis investigates the transport of U, Th and other metals in the boreal landscape by comparing a set of catchments with contrasting characteristics, ranging from 0.12-68 km2 in area. Using uranium (234U/238U) and oxygen isotopes (δ18O) it was demonstrated that catchment size has a strong impact on the hydrological pathways and on the mobilisation of uranium. Both tracers also displayed a consistent shift towards more superficial sources and more superficial flow pathways when going from winter baseflow conditions to the spring flood. Large spatiotemporal variability was observed with U fluxes ranging from 1.7 -30 g km-2 a-1. Using a wide set of hydrochemical parameters and landscape characteristics it was demonstrated that wetlands play a decisive role for the biogeochemical cycling of many metals. Comparing normalised fluxes of 13 different elements (Al, Ba, Ca, Cr, Cu, La, Mg, Na, Ni, Si, Sr, U and Y) 73% of the spatial variance could be explained based on the wetland coverage and the affinity for organic matter, the latter of which was quantified using thermodynamic modelling. Hence, it was possible to link the large-scale transport patterns of a wide range of metals to fundamental biogeochemical properties. When restraining the analysis to the smaller streams (<10 km2), the explanatory power increased to 88%. For elements such as Na and Si with low affinity for organic matter the decrease in wetland-dominated catchments corresponded closely to the area of mineral soils that had been replaced by peat, indicating that reduced weathering was the main cause of the decrease. For organophilic metals the decrease in wetland-dominated catchments was even greater, suggesting that there also was an accumulation of these metals in the peat. This was confirmed by investigating the distribution of radionuclides in local mire, which revealed considerable accumulation of uranium and thorium along the edges of the mire. Based on the inventories of uranium and thorium and their distribution in the peat it was concluded that the mire historically had been a sink for these metals and that it most likely will continue to be so for a long time to come. All and all, wetlands were estimated to decrease the fluxes of metals from the boreal forests to downstream lakes and oceans by 20-40%, depending on how strongly they bind to organic matter.

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    Radionuclide Transport in the Boreal Landscape
  • 25.
    Lidman, Fredrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Mörth, Carl-Magnus
    Dept. of Geology and Geochemistry, Stockholm University, Stockholm, Sweden.
    Laudon, Hjalmar
    Dept. of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Landscape control of uranium and thorium in boreal streams: spatiotemporal variability and the role of wetlands2012In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 9, no 11, p. 4773-4785Article in journal (Refereed)
    Abstract [en]

    The concentrations of uranium and thorium in ten partly nested streams in the boreal forest region were monitored over a two-year period. The investigated catchments ranged from small headwaters (0.1 km(2)) up to a fourth-order stream (67 km(2)). Considerable spatiotemporal variations were observed, with little or no correlation between streams. The fluxes of both uranium and thorium varied substantially between the subcatchments, ranging from 1.7 to 30 g km(-2) a(-1) for uranium and from 3.2 to 24 g km(-2) a(-1) for thorium. Airborne gamma spectrometry was used to measure the concentrations of uranium and thorium in surface soils throughout the catchment, suggesting that the concentrations of uranium and thorium in mineral soils are similar throughout the catchment. The fluxes of uranium and thorium were compared to a wide range of parameters characterising the investigated catchments and the chemistry of the stream water, e. g. soil concentrations of these elements, pH, TOC (total organic carbon), Al, Si and hydrogen carbonate, but it was concluded that the spatial variabilities in the fluxes of both uranium and thorium mainly were controlled by wetlands. The results indicate that there is a predictable and systematic accumulation of both uranium and thorium in boreal wetlands that is large enough to control the transport of these elements. On the landscape scale approximately 65-80% of uranium and 55-65% of thorium entering a wetland were estimated to be retained in the peat. Overall, accumulation in mires and other types of wetlands was estimated to decrease the fluxes of uranium and thorium from the boreal forest landscape by 30-40%, indicating that wetlands play an important role for the biogeochemical cycling of uranium and thorium in the boreal forest landscape. The atmospheric deposition of uranium and thorium was also quantified, and its contribution to boreal streams was found to be low compared to weathering.

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  • 26.
    Lidman, Fredrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Peralta Tapia, Andres
    Dept. of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Vesterlund, Anna
    Swedish Defence Research Agency (FOI), Umeå, Sweden.
    Laudon, Hjalmar
    Dept. of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    234U/238U and 18O in a boreal stream network: comparing two tracers for deep groundwater dischargeManuscript (preprint) (Other academic)
    Abstract [en]

    Uranium (234U/238U) and oxygen (δ18O) isotopes were measured in eight boreal streams and in seven deep groundwater wells adjacent to these streams. The measurements covered an entire spring flood cycle from winter baseflow conditions, through the peak flow and into the early summer, thereby capturing much of the hydrological dynamics in these systems. In the groundwater higher 234U/238U ratios were found in the larger catchments, indicating that long transit times and deep hydrological pathways are reflected in the uranium isotope signature. This was also supported by the δ18O signals and the Ca/Mg ratio in the groundwater. A similar dependence on the catchment area was observed in the streams, which during baseflow conditions generally displayed higher 234U/238U ratios in the larger streams. This relationship remained as the peak flood arrived, although it coincided with a general decrease in the 234U/238U ratios. Simultaneously, the δ18O signal dropped, indicating a greater influence of meltwater. Combined the two isotope pairs suggest that the spring flood leads to more superficial hydrological pathways and more superficial sources of uranium. In connection with the spring flood there was a strong, nearly 1:1 relationship between the streams and the adjacent groundwater wells in terms of 234U/238U ratios. However, the streams generally tended to have higher 234U/238U ratios than the deep groundwater, which in turn had higher uranium concentrations. No correlation was found between 234U/238U ratios and uranium concentrations in any of the analysed waters, and no difference in 234U/238U ratios could be observed between different landscape types. All and all, the results demonstrate that 234U/238U and δ18O generally provide a consistent view of the functioning of the investigated catchment in terms of hydrology and element transport.

  • 27.
    Lidman, Fredrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Peralta-Tapia, Andres
    Vesterlund, Anna
    Laudon, Hjalmar
    U-234/U-238 in a boreal stream network: relationship to hydrological events, groundwater and scale2016In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 420, p. 240-250Article in journal (Refereed)
    Abstract [en]

    Uranium isotopes (U-234/U-238) were measured in eight well-studied boreal streams of different sizes and characters and in seven deep groundwater wells (up to 11m deep) adjacent to these streams. The measurements covered an entire spring flood cycle, from winter baseflow conditions, through the peak flow and into the early summer, thereby capturing much of the hydrological dynamics in these systems. To deepen the interpretation of the spatiotemporal variability of the U-234/U-238 ratio a wide range of hydrochemical and geographical data were included in the analysis. Special attention was given to delta O-18, the most widely used isotopic tracer for hydrological pathways and groundwater transit times, because high U-234/U-238 ratios have often traditionally been attributed to input of deep groundwater and long transit times. The results demonstrated that there was generally a gradual increase in U-234/U-238 ratios in groundwater with increasing catchment area, which based on delta O-18 data was caused by deeper groundwater pathways and longer residence times in larger catchments. A similar dependence on the catchment area was observed in the streams, which during baseflow conditions generally displayed higher U-234/U-238 ratios in the larger streams. This relationship remained as the peak flow arrived, although it coincided with a general decrease in the U-234/U-238 ratios. Simultaneously, the delta O-18 signal dropped, indicating a greater influence of meltwater and younger groundwater. When combined, this confirmed that the activation of shallower groundwater pathways in connection with the spring flood also activated shallower sources of uranium. In connection with the spring flood there was a strong, nearly 1:1 relationship between the streams and the adjacent groundwater wells in terms of U-234/U-238 ratios, suggesting that the Quaternary deposits were the main source for uranium. Despite large differences in uranium concentrations between different landscape types no effects could be seen on the isotope signature, indicating that the U-234/U-238 ratio is a reliable tracer for the primary source and that the fractionation after mobilisation probably is negligible. All in all, the results demonstrated that U-234/U-238 ratios and delta O-18 generally provide a consistent picture of the hydrological and bio-geochemical functioning of the investigated catchment.

  • 28.
    Liem-Nguyen, Van
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Skyllberg, Ulf
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Thermodynamic Modeling of the Solubility and Chemical Speciation of Mercury and Methylmercury Driven by Organic Thiols and Micromolar Sulfide Concentrations in Boreal Wetland Soils2017In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 51, no 7, p. 3678-3686Article in journal (Refereed)
    Abstract [en]

    Boreal wetlands have been identified as environments in which inorganic divalent mercury (HgII) is transformed to methylmercury (MeHg) by anaerobic microbes. In order to understand this transformation and the mobility and transport of HgII and MeHg, factors and conditions in control of the solubility and chemical speciation of HgII and MeHg need to be clarified. Here we explore the ability of thermodynamic models to simulate measured solubility of HgII and MeHg in different types of boreal wetland soils. With the input of measured concentrations of MeHg, sulfide, eight low molecular mass thiols and thiol groups associated with natural organic matter (NOM), as determined by sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy and Hg LIII-edge extended X-ray absorption fine structure spectroscopy (EXAFS),the model could accurately predict porewater concentrations of MeHg in the wetlands. A similar model for HgII successfully predicted the average level of its concentration in the porewaters, but the variability among samples, driven mainly by the concentration of aqueous inorganic sulfide, was predicted to be larger than measurements. The smaller than predicted variability in HgII solubility is discussed in light of possible formation of colloidal HgS(s) passing the 0.22 μm filters used to define the aqueous phase. The chemical speciation of the solid/adsorbed and aqueous phases were dominated by NOM associated thiol complexes for MeHg and by an equal contribution from NOM associated thiols and HgS(s) for HgII.

  • 29.
    Ligtenberg, Jora
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lake condition changes of a boreal lake over the past ca. 6500 years based on varve geochemistry2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this study was to assess changes in the in-lake conditions of lake Kassjön, northern Sweden, in response to environmental and climate changes over the past ca. 6500 years. Sediment concentrations of different elements and biogenic silica (bSi) were measured with wavelength dispersive X-ray fluorescence spectrometry (XRF) and Fourier transform infrared spectroscopy (FTIR), respectively. The lake-water total organic carbon (LWTOC) content was inferred based on near-infrared spectroscopy (NIRS). The marine sediment was distinguished from the lacustrine sediment by higher dry bulk density, lithogenic element concentrations and Br content, and lower bSi concentrations. After lake formation, the dry bulk density, lithogenic element concentrations and metal contents decreased, while organic matter (OM), bSi and LWTOC increased. The main reasons for these changes are soil development and vegetation establishment. Spruce immigration around 3000 BP induced considerable changes to the sediment concentrations indicative of increased erosion versus weathering, and LWTOC declined. These changes are mainly related the different characteristics of spruce compared to birch. Human influences in the catchment were also clearly visible, but the rest of the sediment sequence demonstrated that natural changes can be of a similar magnitude. Overall, relatively small-scale, catchment specific processes seem to be more important for changes in the lake conditions than general climate change.

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    master's thesis Jora Ligtenberg
  • 30.
    Linderholm, Johan
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Macphail, Richard
    University College London, UK.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Östman, Sofi
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Eriksson, Samuel
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Wallin, Jan-Erik
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab. Pollenlaboratoriet i Umeå AB.
    Engelmark, Roger
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Ørlandet Iron Age settlement pattern development: Geoarchaeology (geochemistry and soil micromorphology) and plant macrofossils2019In: Environment and Settlement: Ørland 600 BC–AD 1250 / [ed] Ingrid Ystgaard, Nordic Open Access Scholarly Publishing (NOASP) , 2019, p. 107-134Chapter in book (Refereed)
    Abstract [en]

    Macrofossil and geoarchaeological data from a variety of contexts and periods at Vik can provide either in situ or proxyinformation on the human – environment interactions at the site through time. The aim of this paper is to discuss settlementactivity patterns through time and space, with special emphasis on agriculture and animal husbandry strategies. The calcareousshell bank deposits at the site led to a reduction of the amount of analysed citric soluble phosphate and are apparentlyalso linked to very poor macrofossil preservation. The analysis shows that farming in the pre-Roman Iron Age involvedanimal management and manuring of fields where naked and hulled barley were cultivated. Stock was kept in the long houses.There are also indications that animals grazed along the shore. In the Roman Iron Age there is no clear evidence of keepinglivestock indoors; byre residues were instead found in house-associated waste heaps, where chemical data indicate thatdung was left to ferment. Near-house Roman Iron Age waste deposits were also characterised by latrine and fish processingwaste, as well as by high temperature artisan residues – fuel ash and iron working materials. Analysis of soil chemical samplesindicates an increase and intensification of occupation over time during the pre-Roman Iron Age and the Roman Iron Age.Viking-medieval features were also a remarkable source for monitoring latrine, byre and industrial waste, including the secondaryuse of water holes and wells that supplied water to both people and animals.

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  • 31.
    Monteux, Sylvain
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    A song of ice and mud: Interactions of microbes with roots, fauna and carbon in warming permafrost-affected soils2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Permafrost-affected soils store a large quantity of soil organic matter (SOM) – ca. half of worldwide soil carbon – and currently undergo rapid and severe warming due to climate change. Increased SOM decomposition by microorganisms and soil fauna due to climate change, poses the risk of a positive climate feedback through the release of greenhouse gases. Direct effects of climate change on SOM decomposition, through such mechanisms as deepening of the seasonally-thawing active layer and increasing soil temperatures, have gathered considerable scientific attention in the last two decades. Yet, indirect effects mediated by changes in plant, microbial, and fauna communities, remain poorly understood. Microbial communities, which may be affected by climate change-induced changes in vegetation composition or rooting patterns, and may in turn affect SOM decomposition, are the primary focus of the work described in this thesis.

    We used (I) a field-scale permafrost thaw experiment in a palsa peatland, (II) a laboratory incubation of Yedoma permafrost with inoculation by exotic microorganisms, (III) a microcosm experiment with five plant species grown either in Sphagnum peat or in newly-thawed permafrost peat, and (IV) a field-scale cold season warming experiment in cryoturbated tundra to address the indirect effects of climate change on microbial drivers of SOM decomposition. Community composition data for bacteria and fungi were obtained by amplicon sequencing and phospholipid fatty acid extraction, and for collembola by Tullgren extraction, alongside measurements of soil chemistry, CO2 emissions and root density.

    We showed that in situ thawing of a palsa peatland caused colonization of permafrost soil by overlying soil microbes. Further, we observed that functional limitations of permafrost microbial communities can hamper microbial metabolism in vitro. Relieving these functional limitations in vitro increased cumulative CO2 emissions by 32% over 161 days and introduced nitrification. In addition, we found that different plant species did not harbour different rhizosphere bacterial communities in Sphagnum peat topsoil, but did when grown in newly-thawed permafrost peat. Plant species may thus differ in how they affect functional limitations in thawing permafrost soil. Therefore, climate change-induced changes in vegetation composition might alter functioning in the newly-thawed, subsoil permafrost layer of northern peatlands, but less likely so in the topsoil. Finally, we observed that vegetation encroachment in barren cryoturbated soil, due to reduced cryogenic activity with higher temperatures, change both bacterial and collembola community composition, which may in turn affect soil functioning.

    This thesis shows that microbial community dynamics and plant-decomposer interactions play an important role in the functioning of warming permafrost-affected soils. More specifically, it demonstrates that the effects of climate change on plants can trickle down on microbial communities, in turn affecting SOM decomposition in thawing permafrost.

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  • 32. Pearson, Emma J.
    et al.
    Juggins, Steve
    Talbot, Helen M.
    Weckstrom, Jan
    Rosén, Peter
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ryves, David B.
    Roberts, Stephen J.
    Schmidt, Roland
    A lacustrine GDGT-temperature calibration from the Scandinavian Arctic to Antarctic: Renewed potential for the application of GDGT-paleothermometry in lakes2011In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 75, no 20, p. 6225-6238Article in journal (Refereed)
    Abstract [en]

    Quantitative climate reconstructions are fundamental to understand long-term trends in natural climate variability and to test climate models used to predict future climate change. Recent advances in molecular geochemistry have led to calibrations using glycerol dialkyl glycerol tetraethers (GDGTs), a group of temperature-sensitive membrane lipids found in Archaea and bacteria. GDGTs have been used to construct temperature indices for oceans (TEX(86) index) and soils (MBT/CBT index). The aim of this study is to examine GDGT-temperature relationships and assess the potential of constructing a GDGT-based palaeo-thermometer for lakes. We examine GDGT-temperature relationships using core top sediments from 90 lakes across a north-south transect from the Scandinavian Arctic to Antarctica including sites from Finland, Sweden, Siberia, the UK, Austria, Turkey, Ethiopia, Uganda, Chile, South Georgia and the Antarctic Peninsula. We examine a suite of 15 GDGTs, including compounds used in the TEX(86) and MBT/CBT indices and reflecting the broad range of GDGT inputs to small lake systems. GDGTs are present in varying proportions in all lakes examined. The TEX(86) index is not applicable to our sites because of the large relative proportions of soil derived and methanogenic components. Similarly, the MBT/CBT index is also not applicable and predicts temperatures considerably lower than those measured. We examine relationships between individual GDGT compounds and temperature, pH, conductivity and water depth. Temperature accounts for a large and statistically independent fraction of variation in branched GDGT composition. We propose a GDGT-temperature regression model with high accuracy and precision (R(2) = 0.88; RMSE = 2.0 degrees C; RMSEP = 2.1 degrees C) for use in lakes based on a subset of branched GDGT compounds and highlight the potential of this new method for reconstructing past temperatures using lake sediments. (C) 2011 Elsevier Ltd. All rights reserved.

  • 33. Renson, V
    et al.
    Martinez-Cortizas, A
    Mattielli, N
    Coenaerts, J
    Sauvage, C
    De Vleeschouwer, F
    Lorre, C
    Vanhaecke, F
    Bindler, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rautman, M
    Nys, K
    Claeys, Ph
    Lead isotopic analysis within a multiproxy approach to trace pottery sources. The example of White Slip II sherds from Late Bronze Age sites in Cyprus and Syria.2013In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 28, p. 220-234Article in journal (Refereed)
    Abstract [en]

    Lead isotope analyses were carried out on fragments of White Slip II ware, a Late Bronze Age Cypriote pottery ware, and on raw materials possibly used for their production. Sherds originate from three Late Bronze Age sites (Hala Sultan Tekke and Sanidha in Cyprus and Minet el-Beida in Syria) and clays come from the surroundings of Sanidha, a production site for White Slip ware. X-ray fluorescence (XRF) and a Principal Component Analysis (PCA) are combined with Pb isotope analyses to further investigate the effectiveness of the latter method within a multiproxy approach for pottery provenance study. The pottery sherds from the three sites are compared between themselves and with potential raw material. Additional X-ray diffraction (XRD) and analyses using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray detection (EDX) facility were performed on selected sherds and clays. This work confirms that the clay source used for pottery production in Sanidha derives from local weathered gabbro. It also shows that different origins can be proposed for White Slip II ware sherds from Hala Sultan Tekke and Minet el-Beida and that clays were prepared prior to White Slip II ware production. It finally confirms the effectiveness of Pb isotopes in tracing pottery provenance not only by comparing sherd assemblages but also by comparing sherds to potential raw materials. (C) 2012 Elsevier Ltd. All rights reserved.

  • 34.
    Robygd, Joakim
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Effekten av kvävegödsling på gasproduktionen vintertid i boreala sjöar2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    To investigate effects of nitrogen on in-lake CO2 and CH4 production during winter, three pair of lakes was subject for a fertilizing experiment in which one lake in each pair was fertilized with nitric acid (HNO3) directly into the water column in the summer of 2012. The lakes in each pair are assumed to be morphologically, hydrologically and biologically similar, that is, the non-fertilized lakes are considered references. The pairs do differ in one major way by being progressively less humic, going from around 25 mg/l to 10 mg/l DOC. Sampling and analysis was carried out at the end of the frozen period in 2013. Results show a significantly higher concentration of both CO2 (p<0,001) and CH4 (α=0,1, p=0,053) between impact and reference sites in the two less humic pairs. The very humic pair generated lower concentrations of CO2 and CH4 after fertilization in the impact site compared to the reference site. The lakes with low and intermediate humic content are assumed to have increased their biomass production during the ice-free season which contributed to elevated amount of available organic carbon to be mineralized to gas during winter. The absence of a fertilization effect in the very high humic lake is most likely due to light-limitation being the key limitator in that lake, thus preventing an elevated biomass production during the ice-free season. Northern boreal lakes can be expected to react differently to elevated N-deposition and runoff depending on the amount of catchment derived terrestrial carbon transported to the lake.

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    Effekten av kvävegödsling på gasproduktionen vintertid i boreala sjöar
  • 35. Routh, Joyanto
    et al.
    Hugelius, Gustaf
    Kuhry, Peter
    Filley, Timothy
    Tillman, Paivi Kaislahti
    Becher, Marina
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Crill, Patrick
    Multi-proxy study of soil organic matter dynamics in permafrost peat deposits reveal vulnerability to climate change in the European Russian Arctic2014In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 368, p. 104-117Article in journal (Refereed)
    Abstract [en]

    Soil organic carbon (SOC) in permafrost terrain is vulnerable to climate change. Perennially frozen peat deposits store large amounts of SOC, but we know little about its chemical composition and lability. We used plant macrofossil and biomarker analyses to reconstruct the Holocene paleovegetation and paleoenvironmental changes in two peat plateau profiles from the European Russian Arctic. Peat plateaus are the main stores of permafrost soil C in the region, but during most of the Holocene peats developed as permafrost-free rich fens with woody vegetation, sedges and mosses. Around 2200 cal BP, permafrost aggraded at the site resulting in frost heave and a drastic reduction in peat accumulation under the drier uplifted surface conditions. The permafrost dynamics (aggradation, frost-heave and thaw) ushered changes in plant assemblages and carbon accumulation, and consequently in the biomarker trends too. Detailed biomarker analyses indicate abundant neutral lipids, which follow the general pattern: n-alkanols > sterols >= n-alkanes >= triterpenols. The lignin monomers are not as abundant as the lipids and increase with depth. The selected aliphatic and phenolic compounds are source specific, and they have different degrees of lability, which is useful for tracing the impact of permafrost dynamics (peat accumulation and/or decay associated with thawing). However, common interpretation of biomarker patterns, and perceived hydrological and climate changes, must be applied carefully in permafrost regions. The increased proportion (selective preservation) of n-alkanes and lignin is a robust indicator of cumulative decomposition trajectories, which is mirrored by functional compounds (e. g. n-alkanol, triterpenol, and sterol concentrations) showing opposite trends. The distribution of these compounds follows first order decay kinetics, and concurs with the down core diagenetic changes. In particular, some of the biomarker ratios (e. g. stanol/sterol and higher plant alkane index) seem promising for tracing SOC decomposition despite changes in botanical imprint, and sites spanning across different soil types and locations. Carbon accumulation rate calculated at these sites varies from 18.1 to 31.1 gC m(-2) yr(-1), and it's evident selective preservation, molecular complexity of organic compounds, and freezing conditions enhance the long-term stability of SOC. Further, our results suggest that permafrost dynamics strongly impact the more undecomposed SOC that could be rapidly remobilized through ongoing thermokarst expansion.

    (C) 2014 Elsevier B. V. All rights reserved.

  • 36. Sar, Suchandra
    et al.
    Öqvist, Lena Sundqvist
    Sparrman, Tobias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Engström, Fredrik
    Samuelsson, Caisa
    Characterization of Double Leached Waelz Oxide for Identification of Fluoride Mineral2019In: Metals, ISSN 2075-4701, Vol. 9, no 3, article id 361Article in journal (Refereed)
    Abstract [en]

    Double leached Waelz oxide (DLWO), with 76% zinc, is a secondary zinc containing raw materials obtained by the treatment of electric arc furnace dust. The content of fluoride in DLWO is still too high for direct leaching, as fluoride has a detrimental effect on electrowinning for zinc production. Knowledge of the characteristics of DLWO, and especially on how a fluoride mineral might exist, can contribute to further improvement of the selective leaching for the removal of fluoride. In this study, DLWO was characterized using analytical techniques, such as inductively coupled plasma-optical emission spectroscopy (ICP-OES), F-19 liquid-state nuclear magnetic resonance (F-19 LS NMR), X-ray powder diffraction analysis (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and F-19 solid-state nuclear magnetic resonance (F-19 SS NMR). This study showed that DLWO mainly consisted of zincite (ZnO), cerussite (PbCO3) and a spinel containing zinc, iron and manganese. The fluoride mineral identified was calcium fluoride (CaF2). In SEM analysis, fluorine was found in larger grains together with calcium and oxygen, which was possibly calcium carbonate.

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  • 37. Schellekens, Judith
    et al.
    Bindler, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Martínez-Cortizas, Antonio
    McClymont, Erin L.
    Abbott, Geoffrey D.
    Biester, Harald
    Pontevedra-Pombal, Xabier
    Buurman, Peter
    Preferential degradation of polyphenols from Sphagnum-4-Isopropenylphenol as a proxy for past hydrological conditions in Sphagnum-dominated peat2015In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 150, p. 74-89Article in journal (Refereed)
    Abstract [en]

    The net accumulation of remains of Sphagnum spp. is fundamental to the development of many peatlands. The effect of polyphenols from Sphagnum on decomposition processes is frequently cited but has barely been studied. The central area of the Rodmossamyran peatland (Sweden) is an open lawn that consists mostly of Sphagnum spp. with a very low contribution from vascular plants. In order to determine the effects of decay on sphagnum phenols, 53 samples of a 2.7 m deep core from this lawn were analysed with pyrolysis gas chromatography-mass spectrometry (pyrolysis-GC-MS) and compared with more traditional decomposition proxies such as C/N ratio, UV light transmission of alkaline peat extracts, and bulk density. Factor analysis of 72 quantified pyrolysis products suggested that the variation in 4-isopropenylphenol was largely determined by aerobic decomposition instead of Sphagnum abundance. In order to evaluate the effects of aerobic decay in Sphagnum peat, down-core records from different climatic regions were compared using molecular markers for plant biopolymers and C/N ratio. These included markers for lignin from vascular plants ((di) methoxyphenols), polyphenols from Sphagnum spp. (4-isopropenylphenol), and cellulose (levoglucosan). Our results indicate that polyphenols from Sphagnum are preferentially degraded over polysaccharides; consequently the variability of the marker for sphagnum acid, 4-isopropenylphenol, was found indicative of decomposition instead of reflecting the abundance of Sphagnum remains. The fact that 4-isopropenylphenol is aerobically degraded in combination with its specificity for Sphagnum spp. makes it a consistent indicator of past hydrological conditions in Sphagnum-dominated peat. In contrast, the variability of C/N records in Sphagnum-dominated peat was influenced by both vegetation shifts and decomposition, and the dominant effect differed between the studied peatlands. Our results provide direction for modelling studies that try to predict possible feedback mechanisms between peatlands and future climate change, and indicate that the focus in Sphagnum decay studies should be on carbohydrates rather than on phenolic compounds.

  • 38.
    Skoglund, Björn
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Diffusive gas fluxes in neotropical rainforest streams2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Rainforests are of great importance to global carbon cycling, but the importance of deforestation and change in land use is poorly understood due to a lack of studies quantifying the difference in carbon fluxes between original rainforest and agricultural land. Furthermore, the aquatic outgassing of neotropical systems have been proven to have greater impact on global carbon cycling than previously anticipated (Richey et al 2002).In this study we investigated the aquatic concentration and daily diffusive gas flux of CO2 and CH4 from 4 pristine sites and 4 impacted sites, respectively, in 4 streams running along a gradient of anthropological impaction in the Atlantic Rainforest, Brazil. Statistically significant differences between pristine and impacted sites were found in all streams for both CO2 and CH4. On average, the impacted sites were found to be emitting almost three times as much C into the atmosphere as the pristine sites, mainly owing to CO2 emissions (14172±5226 mg C m-2 d-1). Exploring an area of the neotropical carbon cycle that is not yet fully understood, the study draws attention to the significant difference in aquatic outgassing from rivers observed at different impaction levels and highlights the need for further field studies.

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  • 39. Soerensen, A. L.
    et al.
    Schartup, A. T.
    Skrobonja, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bouchet, S.
    Amouroux, D.
    Liem-Nguyen, Van
    Umeå University, Faculty of Science and Technology, Department of Chemistry. School of Science and Technology, Örebro University, Örebro, Sweden.
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Deciphering the Role of Water Column Redoxclines on Methylmercury Cycling Using Speciation Modeling and Observations From the Baltic Sea2018In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 32, no 10, p. 1498-1513Article in journal (Refereed)
    Abstract [en]

    Oxygen-depleted areas are spreading in coastal and offshore waters worldwide, but the implication for production and bioaccumulation of neurotoxic methylmercury (MeHg) is uncertain. We combined observations from six cruises in the Baltic Sea with speciation modeling and incubation experiments to gain insights into mercury (Hg) dynamics in oxygen depleted systems. We then developed a conceptual model describing the main drivers of Hg speciation, fluxes, and transformations in water columns with steep redox gradients. MeHg concentrations were 2-6 and 30-55 times higher in hypoxic and anoxic than in normoxic water, respectively, while only 1-3 and 1-2 times higher for total Hg (THg). We systematically detected divalent inorganic Hg (Hg-II) methylation in anoxic water but rarely in other waters. In anoxic water, high concentrations of dissolved sulfide cause formation of dissolved species of Hg-II: HgS2H(aq)- and Hg (SH)(2)(0)((aq)). This prolongs the lifetime and increases the reservoir of Hg-II readily available for methylation, driving the high MeHg concentrations in anoxic zones. In the hypoxic zone and at the hypoxic-anoxic interface, Hg concentrations, partitioning, and speciation are all highly dynamic due to processes linked to the iron and sulfur cycles. This causes a large variability in bioavailability of Hg, and thereby MeHg concentrations, in these zones. We find that zooplankton in the summertime are exposed to 2-6 times higher MeHg concentrations in hypoxic than in normoxic water. The current spread of hypoxic zones in coastal systems worldwide could thus cause an increase in the MeHg exposure of food webs.

  • 40.
    Song, Xiaowei
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boily, Jean-François
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Water vapor adsorptions on goethite surfacesManuscript (preprint) (Other academic)
  • 41.
    Sundman, Anneli
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Interactions between Fe and organic matter and their impact on As(V) and P(V)2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Iron (Fe) speciation is important for many biogeochemical processes. The high abundance and limited solubility of Fe(III) are responsible for the widespread occurrence of Fe(III) minerals in the environment. Co-precipitation and adsorption onto mineral surfaces limits the free concentrations of compounds such as arsenate (As(V)), Fe(III) and, phosphate (P(V)). Mineral dissolution, on the other hand, might lead to elevated concentrations of these compounds. Fe speciation is strongly affected by natural organic matter (NOM), which suppresses hydrolysis of Fe(III) via complexation. It limits the formation of Fe(III) minerals and Fe(III) co-precipitation. This thesis is focused on interactions between Fe(III) and NOM as well as their impact on other elements (i.e. As(V) and P(V)). X-ray absorption spectroscopy (XAS) was used to obtain molecular scale information on Fe and As speciation. This was complemented with infrared spectroscopy, as well as traditional wet-chemical analysis, such as pH and total concentration determinations. Natural stream waters, soil solutions, ground water and soil samples from the Krycklan Catchment, in northern Sweden, were analyzed together with model compounds with different types of NOM. A protocol based on ion exchange resins was developed to concentrate Fe from dilute natural waters prior to XAS measurements. Iron speciation varied between the stream waters and was strongly affected by the surrounding landscape. Stream waters originating from forested or mixed sites contained both Fe(II, III)-NOM complexes and precipitated Fe(III) (hydr)oxides. The distribution between these two pools was influenced by pH, total concentrations and, properties of NOM. In contrast, stream waters from wetland sites and soil solutions from a forested site only contained organically complexed Fe. Furthermore, the soil solutions contained a significant fraction Fe(II)-NOM complexes. The soil samples were dominated by organically complexed Fe and a biotite-like phase. Two pools of Fe were also identified in the ternary systems with As(V) or P(V) mixed with Fe(III) and NOM: all Fe(III) was complexed with NOM at low total concentrations of Fe(III), As(V) and/or P(V). Hence, Fe(III) complexation by NOM reduced Fe(III)-As(V)/P(V) interactions at low Fe(III) concentrations, which led to higher bioavailability. Exceeding the Fe(III)-NOM complex equilibrium resulted in the occurrence of Fe(III)-As(V)/P(V) (co-)-precipitates.

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  • 42.
    Sundman, Anneli
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Karlsson, Torbjörn
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Laudon, Hjalmar
    Persson, Per
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Centre for Environmental and Climate Research & Department of Biology, Lund University, Lund.
    XAS study of iron speciation in soils and waters from a boreal catchment2014In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 364, p. 93-102Article in journal (Refereed)
    Abstract [en]

    Iron (Fe) is a key element, strongly influencing the biogeochemistry of soils, sediments and waters, but the knowledge about the variety of Fe species present in these systems is still limited. In this work we have used X-ray absorption spectroscopy (XAS) to study the speciation of Fe in soils and waters from a boreal catchment in northern Sweden. The aim was to better understand the controls of Fe speciation across different, but adjacent landscape elements including soil, soil solution, groundwater and stream water draining catchments with contrasting land characteristics. Our results showed that all samples contained mixtures of Fe(II) and Fe(III). The soils consisted of Fe phyllosilicates, Fe (hydr)oxides and Fe complexed by natural organic matter (NOM). All aqueous samples contained Fe(II)– and Fe(III)–NOM complexes, often in combination with Fe(III) (hydr)oxides that were associated with NOM. The variation in contribution from Fe–NOM and Fe (hydr)oxides was controlled by pH and total concentrations of NOM. The XAS spectra suggested formation of mononuclear Fe–NOM complexes consisting of chelate ring structures, but it could not be determined whether they originated solely from Fe(III)– or from a mixture of Fe(II)/Fe(III)–NOM complexes. Our collective results showed that the Fe speciation was highly variable across the different landscape elements and streams. This variation was manifested both in the distribution between mononuclear Fe–NOM complexes and Fe (hydr)oxides associated with NOM and between Fe(II) and Fe(III). These results highlight the complexity of Fe speciation in natural environmental systems and thus the challenges in interpreting Fe reactivity.

  • 43.
    Sundman, Anneli
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Karlsson, Torbjörn
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Persson, Per
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Centre of Environmental and Climate Research & Department of Biology, Lund University.
    Reactivity of Fe from a natural stream water towards As(V)Manuscript (preprint) (Other academic)
  • 44.
    Sundman, Anneli
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Karlsson, Torbjörn
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Persson, Per
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Centre of Environmental and Climate Research & Department of Biology, Lund University.
    Complexation and precipitation reactions in the ternary As(V)-Fe(III)-NOM (natural organic matter) systemManuscript (preprint) (Other academic)
  • 45.
    Sundman, Anneli
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Karlsson, Torbjörn
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Persson, Per
    Complexation and precipitation reactions in the ternary As(V)–Fe(III)–OM (organic matter) system2014In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 145, p. 297-314Article in journal (Refereed)
    Abstract [en]

    The predominant forms of arsenic (As) in anoxic and oxic environments are As(III) and As(V), respectively, and the fate of these forms is influenced by interactions with mineral surfaces and organic matter (OM). Interactions between As(V) and OM are believed to occur mainly via iron(Fe)-bridges in ternary Fe–arsenate complexes, but direct evidence for these interactions are scarce. Furthermore, since the speciation of Fe in the presence of organic matter varies as a function of pH and Fe concentration, a central question is how different chemical conditions will affect the As–Fe–OM interactions. In order to answer this, the As(V)–Fe(III)–OM system have been studied under a large range of experimental conditions (6485–67,243 ppm Fe(III) and Fe(III):As(V) ratios of 0.5–20 at pH 3–7), with Suwannee River natural organic matter and Suwannee River fulvic acid as sources of OM, using Fe and As K-edge X-ray absorption spectroscopy (XAS), infrared (IR) spectroscopy and chemical equilibrium modeling. Our collective results showed that interactions in the ternary As(V)–Fe(III)–OM system were strongly influenced by pH, total concentrations and ratios among the reactive species. In particular, the high stability of the Fe(III)–OM complexes exerted a strong control on the speciation. The predominant species identified were mononuclear Fe(III)–OM complexes, Fe(III) (hydr)oxides and FeAsO4 solids. The experimental results also showed that at low concentrations the Fe(III)–OM complexes were sufficiently stable to prevent reaction with arsenate. The chemical equilibrium models developed corroborated the spectroscopic results and indicated that As(V) was distributed over two solid phases, namely FeAsO4(s) and Fe(OH)1.5(AsO4)0.5(s). Thus, neither ternary As(V)–Fe(III)–OM complexes nor As(V) surface complexes on Fe(III) (hydr)oxides were necessary to explain the collective results presented in this study.

  • 46.
    Sundman, Anneli
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Karlsson, Torbjörn
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Persson, Per
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Centre of Environmental and Climate Research & Department of Biology, Lund University.
    Complexation and precipitation reactions in the ternary P(V)-Fe(III)-NOM (natural organic matter) systemManuscript (preprint) (Other academic)
  • 47. Tinnacher, Ruth M.
    et al.
    Holmboe, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Earth and Environmental Sciences Area, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States.
    Tournassat, Christophe
    Bourg, Ian C.
    Davis, James A.
    Ion adsorption and diffusion in smectite: Molecular, pore, and continuum scale views2016In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 177, p. 130-149Article in journal (Refereed)
    Abstract [en]

    Clay-rich media have been proposed as engineered barrier materials or host rocks for high level radioactive waste repositories in several countries. Hence, a detailed understanding of adsorption and diffusion in these materials is needed, not only for radioactive contaminants, but also for predominant earth metals, which can affect radionuclide speciation and diffusion. The prediction of adsorption and diffusion in clay-rich media, however, is complicated by the similarity between the width of clay nanopores and the thickness of the electrical double layer (EDL) at charged clay mineral-water interfaces. Because of this similarity, the distinction between 'bulk liquid' water and 'surface' water (i.e., EDL water) in clayey media can be ambiguous. Hence, the goal of this study was to examine the ability of existing pore scale conceptual models (single porosity models) to link molecular and macroscopic scale data on adsorption and diffusion in compacted smectite. Macroscopic scale measurements of the adsorption and diffusion of calcium, bromide, and tritiated water in Na-montmorillonite were modeled using a multi-component reactive transport approach while testing a variety of conceptual models of pore scale properties (adsorption and diffusion in individual pores). Molecular dynamics (MD) simulations were carried out under conditions similar to those of our macroscopic scale diffusion experiments to help constrain the pore scale models. Our results indicate that single porosity models cannot be simultaneously consistent with our MD simulation results and our macroscopic scale diffusion data. A dual porosity model, which allows for the existence of a significant fraction of bulk liquid water-even at conditions where the average pore width is only a few nanometers-may be required to describe both pore scale and macroscopic scale data.

  • 48.
    Tolu, Julie
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rydberg, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Meyer-Jacob, Carsten
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gerber, Lorenz
    Bindler, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Spatial variability of organic matter molecular composition and elemental geochemistry in surface sediments of a small boreal Swedish lake2017In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 14, no 7, p. 1773-1792Article in journal (Refereed)
    Abstract [en]

    The composition of sediment organic matter (OM) exerts a strong control on biogeochemical processes in lakes, such as those involved in the fate of carbon, nutrients and trace metals. While between-lake spatial variability of OM quality is increasingly investigated, we explored in this study how the molecular composition of sediment OM varies spatially within a single lake and related this variability to physical parameters and elemental geochemistry. Surface sediment samples (0-10 cm) from 42 locations in Harsvatten - a small boreal forest lake with a complex basin morphometry - were analyzed for OM molecular composition using pyrolysis gas chromatography mass spectrometry for the contents of 23 major and trace elements and biogenic silica. We identified 162 organic compounds belonging to different biochemical classes of OM (e.g., carbohydrates, lignin and lipids). Close relationships were found between the spatial patterns of sediment OM molecular composition and elemental geochemistry. Differences in the source types of OM (i.e., terrestrial, aquatic plant and algal) were linked to the individual basin morphometries and chemical status of the lake. The variability in OM molecular composition was further driven by the degradation status of these different source pools, which appeared to be related to sedimentary physicochemical parameters (e.g., redox conditions) and to the molecular structure of the organic compounds. Given the high spatial variation in OM molecular composition within Harsvatten and its close relationship with elemental geochemistry, the potential for large spatial variability across lakes should be considered when studying biogeochemical processes in-volved in the cycling of carbon, nutrients and trace elements or when assessing lake budgets.

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  • 49. Viipsi, K.
    et al.
    Sjöberg, S.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tõnsuaadu, K.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Cd2+ and Zn2+ sorption on apatite in the presence of EDTA and humic substance2013In: Proceedings of the 16th International Conference on Heavy Metals in the Environment / [ed] Pirrone, N, EDP Sciences, 2013, article id 01008Conference paper (Refereed)
    Abstract [en]

    The sorption of Cd2+ and Zn2+ on hydroxyapatite [HAP-Ca-10(PO4)(6)(OH)(2)] and fluorapatite [FAP-Ca-10(PO4)(6)(F)(2)] with different specific surface area and stoichiometry was investigated in batch experiments in the pH range 4 to 11 (25 degrees C; 0.1 M KNO3). The impact of different conditions was concerned: solution pH, the presence of complexing ligands (EDTA and humic substance) and competing metal ions, as well as reaction kinetic and equilibrium conditions. To evaluate the reversibility of Cd2+ sorption onto HAP, desorption characteristics in water, Ca, EDTA, and HUM-solutions were determined. Additionally to solution analysis the surface composition of solid phases was analysed by X-Ray Photoelectron Spectroscopy (XPS). The information from the chemical analyses was used to design an equilibration model that takes into account dissolution, surface potential, solution and surface complexation, as well as possible phase transformations. It was revealed that apatites effectively sorb Cd2+ and Zn2+ by ion exchange reactions on surface by formation of new surface phases. Using XPS the formation of a Me-enriched HAP surface was found, which was interpreted as the formation of a solid solution with the general formula: Ca8.4-xMex(HPO4)(1.6)(PO4)(4.4)(OH)(0.4). In a binary solution (Cd+ Zn) the competition of metals reduced individual sorbed amount compared with the single component solutions but the total adsorption maximum was approximately constant. The presence of EDTA reduces the metal sorption on apatite due to [CdEDTA](2)- and [ZnEDTA] 2-complexes and increases apatite solubility due to [CaEDTA](2)-complex formation. The dissolved humic substance was bound on apatite in suspensions but the amount of Cd2+ bound was not changed. The results showed that the solution pH and the presence of complexing ligands have a significant effect on heavy metal sorption on apatite and must be considered if apatites are used as remediation agent. The proposed model can be used to predict apatite dissolution and surface phase transformations in the presence of metal ions and EDTA.

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  • 50. Wang, Xiaoming
    et al.
    Phillips, Brian L.
    Boily, Jean-Francois
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hu, Yongfeng
    Hu, Zhen
    Yang, Peng
    Feng, Xionghan
    Xu, Wenqian
    Zhu, Mengqiang
    Phosphate Sorption Speciation and Precipitation Mechanisms on Amorphous Aluminum Hydroxide2019In: Soil Systems, ISSN 2571-8789, Vol. 3, no 1, article id 20Article in journal (Refereed)
    Abstract [en]

    Aluminum (Al) oxides are important adsorbents for phosphate in soils and sediments, and significantly limit Phosphate (P) mobility and bioavailability, but the speciation of surface-adsorbed phosphate on Al oxides remains poorly understood. Here, phosphate sorption speciation on amorphous Al hydroxide (AAH) was determined under pH 3-8 and P concentration of 0.03 mM-15 mM using various spectroscopic approaches, and phosphate precipitation mechanisms were discussed as well. AAH exhibits an extremely high phosphate sorption capacity, increasing from 3.80 mmol/g at pH 7 to 4.63 mmol/g at pH 3. Regardless of reaction pH, with increasing P sorption loading, the sorption mechanism transits from bidentate binuclear (BB) surface complexation with d(P-Al) of 3.12 angstrom to surface precipitation of analogous amorphous AlPO4 (AAP), possibly with ternary complexes, such as (equivalent to Al-O)(2)-PO2-Al, as intermediate products. Additionally, the percentage of precipitated phosphate occurring in AAP linearly and positively correlates with P sorption loading. Compared to phosphate reaction with ferrihydrite, phosphate adsorbs and precipitates more readily on AAH due to the higher solubility product (K-sp) of AAH. The formation of AAP particles involves Al-III release, which is promoted by phosphate adsorption, and its subsequent precipitation with phosphate at AAH surfaces or in the bulk solution.

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