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  • 1.
    Augustsson, Anna
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Gaillard, Marie-José
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Peltola, Pasi
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Mazier, Florence
    Bergbäck, Bo
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Saarinen, Timo
    Effects of land use and climate change on erosion intensity and sediment geochemistry at Lake Lehmilampi, Finland2013In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 23, no 9, p. 1247-1259Article in journal (Refereed)
    Abstract [en]

    This paper aims to evaluate the possible relationships between erosion intensity and changes in climate and land use during the past 5.5 cal. k years at Lake Lehmilampi, eastern Finland. In this study we compare a detailed geochemical sediment record with (1) forest and land use history inferred from the first pollen and charcoal records from Lake Lehmilampi, and (2) existing archaeological surveys and independent proxy-records of climate change in the study region. The physical and geochemical sediment parameters examined include grain size analysis data and 23 chemical elements, determined with four selective extractions and ICP-MS. There are indications of possible human impact in the lake catchment as early as the Neolithic period, c. 3000-2550 bc, but the first undisputable signs are dated to 1800-100 bc. Cereal pollen reappears at c. ad 1700 and increases rapidly until c. ad 1950. The Holocene Thermal Maximum, its end c. 2000 bc, and the Medieval Climate Anomaly' were major climate events that had a prominent effect on erosion intensity, while human impact was a more significant factor during the period 3000 bc-ad 800 and from ad 1500 onwards. Although signs of changes in erosion intensity found in the sediment were small in this small catchment, they were significant enough to have a clear impact on the fraction of potentially mobile element species. This fraction increases with decreasing erosion intensity, which is probably related to a higher degree of chemical weathering and leaching during periods of decreased erosion.

  • 2.
    Berger, Tobias
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Gustafsson, Jon Petter
    Kungliga Tekniska Högskolan, Skolan för arkitektur och samhällsbyggnad (ABE), Institutionen för hållbar utveckling, miljövetenskap och teknik (SEED).
    Åström, Mats E.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Aluminium speciation in boreal catchments enriched in fluoride2012Conference paper (Other academic)
  • 3.
    Berger, Tobias
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Mathurin, Frédéric A.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Drake, Henrik
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Åström, Mats E.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Fluoride in groundwater of regolith and bedrock (0-900 meters depth) in a granitoidic setting, SE Sweden2013In: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 77, no 5, p. 691-691Article in journal (Other academic)
  • 4.
    Berger, Tobias
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Mathurin, Frédéric A.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Drake, Henrik
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Åström, Mats E.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Geological, mineralogical and hydrological controls of fluoride in fresh groundwater in Quaternary deposits and bedrock fractures in a coastal area with Proterozoic granitoidsManuscript (preprint) (Other academic)
  • 5.
    Berger, Tobias
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Peltola, Pasi
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Drake, Henrik
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Åström, Mats E.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Fluoride patterns in a boreal stream influenced by bedrock and hydrology2011In: Goldschmidt Conference Abstracts 2011. Mineralogical Magazine, Vol. 75 (3), 2011, p. 517-517Conference paper (Refereed)
  • 6.
    Berger, Tobias
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Peltola, Pasi
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Drake, Henrik
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Åström, Mats E.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Impact of a Fluorine-Rich Granite Intrusion on Levels and Distribution of Fluoride in a Small Boreal Catchment2012In: Aquatic geochemistry, ISSN 1380-6165, E-ISSN 1573-1421, Vol. 18, no 2, p. 77-94Article in journal (Refereed)
    Abstract [en]

    This paper explores the influence of a fluorine-rich granite on fluoride concentration in a small boreal catchment in northern Europe. The materials include stream water and shallow groundwater sampled in spatial and temporal dimensions, and analytical data on fluoride and a number of ancillary variables. Fluoride increased strongly towards the lower reaches of the catchment—at the stream outlet the concentrations were up to 4.2 mg L −1 and 1.6–4.7 times higher than upstream. Additionally, fluoride concentrations were particularly high in groundwater and small surface-water bodies (including quarries) above or in direct contact with the granite and showed a strong inverse correlation with water discharge in the stream. Taken together, these data and patterns pin-point the granite intrusion as the ultimate source, explaining the abundance and distribution of dissolved fluoride within the catchment. The granite most likely deliver fluoride to the stream by three mechanisms: (1) weathering of the fine fraction of glacial deposits, derived from the granite and associated fluorine-rich greisen alterations, (2) large relative input of baseflow, partially originating in the granite and greisen, into the lower reaches during low flow in particular, and (3) water-conducting fractures or fracture zones running through the fluorine-rich granite and greisen.

  • 7.
    Berger, Tobias
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Yu, Changxun
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Drake, Henrik
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Peltola, Pasi
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Svensson, Daniel
    Åström, Mats E.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Fluorine geochemistry of Quaternary deposits in a nemo-boreal catchment with elevated dissolved fluoride in surface waters and groundwaterManuscript (preprint) (Other academic)
  • 8.
    Destouni, Georgia
    et al.
    Stockholm University.
    Asokan, Shilpa
    Stockholm University.
    Augustsson, Anna
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Balfors, Berit
    KTH Royal Institute of Technology.
    Bring, Arvid
    Stockholm University.
    Jaramillo, Fernando
    Stockholm University.
    Jarsjö, Jerker
    Stockholm University.
    Johansson, Emma
    Swedish Nuclear Fuel and Waste Management Co.
    Juston, John
    Stockholm University.
    Levi, Lea
    KTH Royal Institute of Technology.
    Olofsson, Bo
    KTH Royal Institute of Technology.
    Prieto, Carmen
    Stockholm University.
    Quin, Andrew
    Stockholm University.
    Åström, Mats E.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Cvetkovic, Vladimir
    KTH Royal Institute of Technology.
    Biogeochemical Transformation Pathways through the Land-water Geosphere2014Conference paper (Refereed)
    Abstract [en]

    Water on land undergoes and participates in many biogeochemical exchanges and changes. A bits-and-pieces approach to these may miss essential aspects of change propagation and transformation by land-water through different segments of the Earth system. This paper proposes a conceptualization of the entire land-water geosphere as a scale-free catchment-wise organised system (Figure 1), emphasizing four key new system aspects compared to traditional hydrosphere/water cycle view: i) distinction of coastal divergent in addition to traditional convergent catchments; ii) physical and social-ecological system coupling through four main nodal zones/interfaces (surface, subsurface, coastal, observation); iii) flow-transport pathways as system coupling agents; iv) multiple interactions with the anthroposphere as integral system parts. Utilizing this conceptualization, we identify distinct patterns of direct anthropogenic change in large-scale water and waterborne nutrient fluxes, emerging across different parts of the world. In general, its embedment directly in the anthroposphere/technosphere makes land-water a key geosphere for understanding and monitoring human-driven biogeochemical changes. Further progress in system-level understanding of such changes requires studies of land-water as a continuous yet structured geosphere following the proposed spatiotemporal pathways of change propagation-transformation.

  • 9.
    Drake, Henrik
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Heim, Christine
    Göttingen university, Germany.
    Hogmalm, Johan
    Göteborgs universitet.
    Hansen, Bent
    Göttingen university, Germany.
    Fracture zone-scale variation of trace elements and stable isotopes in calcite in a crystalline rock setting2014In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 40, p. 11-24Article in journal (Refereed)
    Abstract [en]

    With an aim to increase the understanding about the isotopic and chemical heterogeneity of calcites in water-conducting fracture zones with different crystalline wall rock compositions at different depths, we present trace element chemistry, isotopic composition (δ18O, δ13C, 87Sr/86Sr) and biomarkers of euhedral low-temperature fracture-coating calcite. Paleohydrogeological fluctuations and wall rock influence on the hydrochemistry in the deep groundwater are explored. Samples are from several fracture zone sub-fractures (at −360 to −740 m), retrieved during an extensive core drilling campaign in Sweden.

    Calcite generally showed fracture zone specific values of δ13C, δ18O and 87Sr/86Sr, which indicates precipitation from relatively homogeneous fluid (similar to the modern groundwater at the site) at the same event in each fracture zone. δ18O and δ13C in the different fracture zones were consistent with precipitation from waters of different salinity and decreasing organic input with depth, respectively. The latter is also supported by biomarkers showing clear indications of SRB-related organic compounds (e.g. iso- and anteiso-C17:0-branched fatty acids), except in the deepest zone. In contrast to the isotopes, variation in trace elements within the fracture zones was generally up to several orders of magnitude. Manganese and REE, as oppose to the other metals, were higher in the shallow fracture zones (112–1130 and 44–97 ppm, respectively) than in the deeper (28–272 and 5–11 ppm, respectively), in agreement with the groundwater composition. Although the rock types varied between and within the different fracture zones, this had insignificant influence on the trace element chemistry of the calcites. Co-variation was generally relatively large for many trace elements, with isometric logratio correlation generally better than 0.75, which indicates that their variation in the calcites is due to variation of Ca in the fracture water, but other local factors, especially uptake in co-precipitating minerals (clay minerals, barite, pyrite and zeolites), but also microbial activity and metal speciation may have influenced the metal incorporation into calcite. These detailed studies of fracture calcite are of importance for the understanding of variation in fluid chemistry and trace metal uptake in fracture zones, adding together with hydrochemical studies detailed information optimal for site characterisation.

  • 10.
    Drake, Henrik
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Ivarsson, Magnus
    University of Southern Denmark, Denmark.
    Tillberg, Mikael
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Whitehouse, Martin
    Swedish Museum of Natural History.
    Kooijman, Ellen
    Swedish Museum of Natural History.
    Ancient Microbial Activity in Deep Hydraulically Conductive Fracture Zones within the Forsmark Target Area for Geological Nuclear Waste Disposal, Sweden2018In: Geosciences, E-ISSN 2076-3263, Vol. 8, no 6, article id 211Article in journal (Refereed)
    Abstract [en]

    Recent studies reveal that organisms from all three domains of life—Archaea, Bacteria, and even Eukarya—can thrive under energy-poor, dark, and anoxic conditions at large depths in the fractured crystalline continental crust. There is a need for an increased understanding of the processes and lifeforms in this vast realm, for example, regarding the spatiotemporal extent and variability of the different processes in the crust. Here, we present a study that set out to detect signs of ancient microbial life in the Forsmark area—the target area for deep geological nuclear waste disposal in Sweden. Stable isotope compositions were determined with high spatial resolution analyses within mineral coatings, and mineralized remains of putative microorganisms were studied in several deep water-conducting fracture zones (down to 663 m depth), from which hydrochemical and gas data exist. Large isotopic variabilities of δ13Ccalcite (−36.2 to +20.2‰ V-PDB) and δ34Spyrite (−11.7 to +37.8‰ V-CDT) disclose discrete periods of methanogenesis, and potentially, anaerobic oxidation of methane and related microbial sulfate reduction at several depth intervals. Dominant calcite–water disequilibrium of δ18O and 87Sr/86Sr precludes abundant recent precipitation. Instead, the mineral coatings largely reflect an ancient archive of episodic microbial processes in the fracture system, which, according to our microscale Rb–Sr dating of co-genetic adularia and calcite, date back to the mid-Paleozoic. Potential Quaternary precipitation exists mainly at ~400 m depth in one of the boreholes, where mineral–water compositions corresponded

  • 11.
    Drake, Henrik
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Tullborg, Eva-Lena
    Terralogica AB, Gråbo, Sweden.
    Hogmalm, Johan
    Göteborgs universitet.
    Åström, Mats E.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Trace metal distribution and isotope variations in low-temperature calcite and groundwaters in granitoid fractures down to 1 km depth2012In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 84, p. 217-238Article in journal (Refereed)
    Abstract [en]

    Studies of low-temperature fracture calcite in Proterozoic or Archaean crystalline rocks are very limited, mainly becausethis calcite usually is, first, not very abundant and second, very fine-grained or forms rims on older (and much more abundant)hydrothermal calcite and is thus difficult to distinguish. Knowledge of chemical characteristics and the correlation withgroundwater chemistry is thus scarce for low-temperature calcite in these settings, and consequently, knowledge of the recentpalaeohydrogeological history is limited. Boreholes drilled with triple-tube technique in the upper 1 km of the Palaeoproterozoiccrystalline crust at Laxemar, SE Sweden, have enabled preservation of fragile and potentially recently formed fractureminerals. Earlier investigations of these boreholes have resulted in an extensive set of groundwater chemistry data from variousdepths, and in detailed knowledge of the fracture mineral assemblages (ranging from 1.8 Ga to present). This has made itpossible to identify and sample low-temperature, potentially recently formed, calcite from water-flowing fractures for whichrepresentative groundwater chemical data exists. This, in turn, provides an opportunity to detailed comparisons of fracturecalcite (age span in the order of million years, with possibility of post-glacial contributes) and groundwater (age in the order ofdecades to more than a million year depending on depth) in terms of both isotopic and geochemical properties, giving input tothe understanding of groundwater history, partition coefficients derived in laboratory experiment, and reliability of calcitegeochemistry in terms of representing the actual source fluid composition. In this study, the focus is on trace elements (Fe,Mg, Mn and Sr), stable isotopes and Sr isotopes and, for the groundwater data set, also aquatic speciation with Visual MINTEQ.An optimised step-by-step sample specific analytical procedure was used for the collection of calcite coatings. The methodsused depended on the crystal homogeneity (one or several calcite generations), discerned by detailed SEM-investigations(back-scatter and cathodo-luminescence). 87Sr/86Sr ratios as well as d18O signatures in calcite are in the range expected for theprecipitates from present-day groundwater, or older groundwater with similar composition (except in sections with a considerableportion of glacial water, where calcite definitely is older than the latest glaciation). Stable carbon isotopes in calcitegenerally show values typically associated with HCO3 originating from soil organic matter but at intermediate depth frequentlywith HCO3 originating from in situ microbial anaerobic oxidation of methane (highly depleted d13C). For one ofthe studied metals – manganese – there was a strong correlation between the sampled calcite coatings and hypothetical calcitepredicted by applying laboratory-based partition coefficients (literature data) on groundwater chemistry for sections correspondingto those where the calcites were sampled. This points to temporal and spatial stability in groundwater Mn/Ca ratiosover millions of years, or even more, and show that it is possible to assess, based on laboratory-derived data on Mn partitioning,past groundwater Mn-composition from fracture calcites. For other metals – Fe, Sr, and Mg – which are expected to interact with co-precipitating minerals to a higher degree than Mn, the correlations between measured and predicted calcitewere weaker for various reasons.

  • 12.
    Drake, Henrik
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Åström, Mats E.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Tullborg, Eva-Lena
    Göteborgs universitet.
    Whitehouse, Martin
    Naturhistoriska riksmuseet.
    Activity of sulfur reducing bacteria in deep bedrock fractures revealed by variability of δ34S in pyrite and dissolved sulphate2013In: Procedia Earth and Planetary Science, E-ISSN 1878-5220, Vol. 7, p. 228-231Article in journal (Refereed)
    Abstract [en]

    Euhedral pyrite crystals coating 46 granite fractures at depths down to nearly 1 km at Laxemar, Sweden, were analysed for sulfur isotopes (δ34Spyr) by in situ SIMS (secondary ion mass spectrometry) analysis. Most of these fractures had corresponding chemical and isotopic groundwater data, providing a unique opportunity of pyrite-sulfate comparison within the same fracture network. Comparison of the isotopic ratios (δ18O, δ13C, 87Sr/86Sr) of co-genetic calcite with the groundwater showed that the sampled fractures carried pyrite and calcite that are of low-temperature origin, and with some exceptions, possibly precipitated from the present groundwater, or similar pre-modern fluids.

    The δ34Spyr showed huge variations across individual crystals (such as -32 to +73‰) and an extreme overall range (-50‰ to +91‰), which can only be explained by the activity of sulfur reducing bacteria (SRB). The most common sub-grain features were an increase in δ34Spyr with crystal growth related to successively higher δ34SSO4 caused by ongoing SRB activity and Rayleigh fractionation in fractures with low flow. The groundwater δ34SSO4 values (+9 to +37‰) are, in particular in the sulfate-poor waters down to -400 m, higher than the anticipated initial values, and this can also be explained by SRB-related Rayleigh distillation. The δ34SSO4 of the groundwater is, however, lower than that required to produce the highest δ34Spyr values, which may be due to the signal of groundwater in low-flow fractures (carrying 34S-rich sulfate and pyrite) being masked in the water data by high-flow parts of the water-flowing structure carrying abundant and less fractionated sulfate.

  • 13.
    Finkelman, Robert B.
    et al.
    University of Texas at Dallas, USA.
    Orem, William H.
    U.S. Geological Survey, USA.
    Plumlee, Geoffrey S.
    U.S. Geological Survey, USA.
    Selinus, Olle
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Applications of geochemistry to medical geology2018In: Environmental geochemistry: site characterization, data analysis and case histories / [ed] Benedetto De Vivo, Harvey E. Belkin & Annamaria Lima, Elsevier, 2018, 2nd ed., p. 435-465Chapter in book (Other academic)
    Abstract [en]

    The discipline of geochemistry provides insights into how the natural environment impacts animal and human health and is the basis for the important subdiscipline of medical geochemistry. Among the more important contributions of medical geochemistry are the maps illustrating the distribution, on various scales, of potentially toxic trace elements. Chemical analyses of surface water and groundwater, stream sediments, and soil horizons have been published by numerous countries covering large geographic regions. Among the most comprehensive compilations is the Geochemical Atlas of Europe containing analytical data on more than 50 elements from stream water, stream sediment, and three soil horizons in 26 countries. Geochemical processes play a variety of important roles in controlling how humans are exposed to potential toxicants in a wide range of geogenic or anthropogenic materials. Once taken up by the body, geogenic materials such as dusts, soils, and water and their contained toxicants can react chemically with the body's fluids, and these chemical interactions can play key roles in toxicity. In addition to the harmful effects of some geogenic materials, certain clays have demonstrated remarkable antimicrobial properties when applied to open wounds with bacterial infections. Numerous case studies illustrate the potential human health impacts of organic compounds from geogenic sources, and especially those from fossil energy deposits. This is a challenging area of study since disease(s) resulting from exposures may be chronic rather than acute, and involve complex mixtures of substances. Medical geochemistry can play a key role in helping to protect the safety of drinking water by identifying the sources, concentrations, and forms of potentially harmful elements such as arsenic, mercury, and fluorine in natural waters. Chemical and mineralogical characterization of coals has helped to identify the sources of health problems afflicting millions of people worldwide.

  • 14.
    Khoshkhoo, Mohammad
    et al.
    Luleå University of Technology, Sweden.
    Dopson, Mark
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Engström, Fredrik
    Luleå University of Technology, Sweden.
    Sandström, Åke
    Luleå University of Technology, Sweden.
    New insights into the influence of redox potential on chalcopyrite leaching behaviour2017In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 100, p. 9-16Article in journal (Refereed)
    Abstract [en]

    Chalcopyrite (CuFeS2) is the most economically important and most refractory copper mineral when treated in conventional sulphate media leaching systems. In this study, the effect of solution redox potential on leaching of a pure and a pyritic chalcopyrite concentrate was investigated using concentrates with fresh and aged surfaces. In experiments using concentrates with fresh surfaces, the response to redox potential depended on the presence of pyrite: fresh pyritic concentrate leached more effectively at low redox potential (in agreement with reductive leaching mechanisms), while the leaching efficiencies from fresh pure concentrate were similar at high and low redox potentials. The data suggested that the reductive leaching mechanism does not necessarily result in higher and faster recoveries in the absence of the galvanic interaction induced by the presence of pyrite. It was also found that exposure of chalcopyrite to atmospheric oxidation prior to leaching (ageing) had an effect on leaching behaviour in response to redox potential: copper recoveries in leaching of aged concentrates were higher at high redox potentials. This behaviour was attributed to the presence of iron-oxyhydroxides on the surface of aged concentrates. Based on the data from this investigation and previous surface studies, it is proposed that iron-oxyhydroxides play an important role in triggering the hindered dissolution of chalcopyrite. (C) 2016 Elsevier Ltd. All rights reserved.

  • 15. Lohm, Ulrik
    et al.
    Anderberg, Stefan
    Bergbäck, Bo
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Industrial metabolism at the national level: a case study on chromium and lead pollution in Sweden, 1880-19801994In: Industrial metabolism: restructuring for sustainable development / [ed] Robert U. Ayres and Udo E. Simonis, Tokyo: United Nations University Press, 1994, 1, p. 103-118Chapter in book (Other academic)
  • 16.
    Maskenskaya, Olga
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Drake, Henrik
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Hogmalm, Johan
    University of Gothenburg.
    Fallick, Anthony
    Scottish Universities Environmental Research Centre.
    Åström, Mats E.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Abundance and fractionation of rare earth elements in Ca/Al silicate-, calcite-, and fluorite-bearing hydrothermal veins related to Mesoproterozoic anorogenic fluorine-rich granitic intrusionsManuscript (preprint) (Other academic)
  • 17.
    Maskenskaya, Olga
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Drake, Henrik
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Hogmalm, Johan
    University of Gothenburg.
    Fallick, Anthony
    Scottish Universities Environmental Research Centre.
    Åström, Mats E.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Source and fractionation of rare earth elements and yttrium in Paleozoic multi-mineral veins in crystalline bedrock on the Baltic ShieldManuscript (preprint) (Other academic)
  • 18.
    Maskenskaya, Olga
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Drake, Henrik
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Mathurin, Frédéric A.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Åström, Mats E.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Rare earth elements in low-temperature calcite precipitates in fractures in the upper kilometre of Proterozoic crystalline rockManuscript (preprint) (Other academic)
  • 19.
    Maskenskaya, Olga M.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Abundance and fractionation of rare earth elements in calcite and other secondary minerals in fractures in the upper kilometre of crystalline bedrock, SE Sweden2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis focuses on the geochemistry of secondary minerals, mainly calcite but also others such as fluorite and Ca/Al silicates, precipitated throughout the last 1.5 billion years in fractures of crystalline rock, SE Sweden. The work was based on previous reconnaissance studies and has been possible thanks to access to high-quality drill cores and associated mapping data provided by the Swedish Nuclear Fuel and Waste Management Co (SKB). Concentrations of rare earth elements (REEs) and occasionally other metals were determined in a variety of secondary minerals from fractures (mainly open systems) and veins (mainly sealed systems) and in primary minerals from the bedrock. Stable-isotope composition was measured in the secondary minerals. The overall aim was to define the sources, uptake and fractionation of REEs in calcite, and a few other co-genetic minerals, precipitated throughout the geological history under conditions ranging from hydrothermal to low temperatures.

    Collectively, the findings of the individual studies show that there is no easy and straightforward control of REE abundance and fractionation in calcite and other minerals in fractures and veins in crystalline bedrock settings. For example, the REE features in calcite vary extensively within sub-generations of single vein-precipitating events, on micro scale in transects across individual veins, and unsystematically over the geological history characterised by successively decreasing temperatures of mineral formation. Although the REE content in, and release from, the crystalline bedrock can have an influence on REE distribution in calcite and other minerals, it is of overall minor importance within a given bedrock domain. The main advantage of determining REEs in secondary minerals in fractures and veins in crystalline rock is therefore, as revealed in this work, to assess the character and evolution of the conditions (including features of the paleofluids) during confined mineral-precipitating events.

    Download full text (pdf)
    Olga Maskenskaya, Doctoral Thesis (Kappa)
  • 20.
    Maskenskaya, Olga M.
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Drake, Henrik
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Broman, Curt
    Stockholm University.
    Hogmalm, Johan
    University of Gothenburg.
    Czuppon, G.
    Institute for Geological and Geochemical Research, Research Center for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Budapest, Hungary.
    Åström, Mats E.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Source and character of syntaxial hydrothermal calcite veins in Paleoproterozoic crystalline rocks revealed by fine-scale investigations2014In: Geofluids, ISSN 1468-8115, E-ISSN 1468-8123, Vol. 14, no 4, p. 495-511Article in journal (Refereed)
    Abstract [en]

    Calcite veins in Paleoproterozoic granitoids on the Baltic Shield are the focus of this study. These veins are distinguished by their monomineralic character, unusual thickness and closeness to Neoproterozoic dolerite dykes and therefore have drawn attention. The aim of this study was to define the source of these veins and to unravel their isotopic and chemical nature by carrying out fine-scale studies. Seven calcite veins covering a depth interval of 50–420 m below the ground surface and composed of breccias or crack-sealed fillings typically expressing syntaxial growth were sampled and analysed for a variety of physicochemical variables: homogenization temperature (Th) and salinity of fluid inclusions, and stable isotopes (87Sr/86Sr, 13C/12C, 18O/16O), trace-element concentrations (Fe, Mn, Mg, Sr, rare earth elements) and cathodoluminescence (CL) of the solid phase. The fluid-inclusion data show that the calcites were precipitated mainly from relatively low-temperature (Th = 73–106°C) brines (13.4–24.5 wt.% CaCl2), and the 87Sr/86Sr is more radiogenic than expected for Rb-poor minerals precipitated from Neoproterozoic fluids. These features, together with the distribution of δ13C and δ18O values, provide evidence that the calcite veins are not genetic with the nearby Neoproterozoic dolerite dykes, but are of Paleozoic age and were precipitated from warm brines expressing a rather large variability in salinity. Whereas the isotopic and chemical variables express rather constant average values among the individual veins, they vary considerably on fine-scale across individual veins. This has implications for understanding processes causing calcite-rich veins to form and capture trace metals in crystalline bedrock settings.

  • 21.
    Maskenskaya, Olga M.
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Drake, Henrik
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Mathurin, Frédéric A.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Åström, Mats E.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    The role of carbonate complexes and crystal habit on rare earth element uptake in low-temperature calcite in fractured crystalline rock2015In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 391, p. 100-110Article in journal (Refereed)
    Abstract [en]

    This study focuses on rare earth element (REE) geochemistry of low-temperature calcite coatings occurring on the walls of fractures throughout the upper kilometer of crystalline rocks of the Baltic Shield. Fifty one calcite coatings were sampled from cores drilled with the triple-tube technique which successfully preserved the fragile calcite coatings on the fracture walls. The calcites, which based on geological and isotopic evidence were precipitated over the last 10 million years, had highly variable Sigma REE concentrations (0.61-2276 ppm) that decreased weakly with the depth the calcite was sampled from. When normalized to shale (and host rock), the REE concentrations of habits with c-axis approximate to a-axes and the closely associated c-axis > a-axes, the most abundant crystal morphologies in the system, decreased strongly and smoothly across the series. In contrast, the REEs of habits with c-axis >> a-axes, identified only in fractures in the uppermost 260m of the bedrock, were flatter and occasionally expressed a weak middle REE enrichment. By using calcite-water partition coefficients derived for REEs in previous laboratory experiments, the La/Yb of the paleogroundwater from which the calcites precipitated was back-calculated and found to be overall similar (range 0.15-452) overlap to the corresponding ratio of the present groundwater (range: 2.1-36.4). In terms of REE/Ca, the values for the back-calculated paleogroundwater (La / Ca 9.9 (*) 10(-11)-3.9 (*) 10(-7); Yb / Ca 1.5 (*) 10(-10)-2.2(*)10(-7)) were similar to those of LaCO3+ / Ca (4.5(*)10(-10)-8.5 (*) 10(-7)) and (YbCO3+ + Yb(CO3)(2)(-)) / Ca (5.4 (*) 10(-11)-1.8 (*) 10(-8)), respectively, in the present groundwater. These patterns indicate that the LREE to HREE and REE to Ca ratios in the groundwater at the site are broadly similar to those existing when the calcites precipitated, and that carbonate complexes present in the paleogroundwater played a crucial role in sequestration and fractionation of REEs in calcite. The findings have implications for bedrock storage of high-level radioactivewaste, which contains actinides for which the REEs can be used as natural analogues. (C) 2014 Elsevier B.V. All rights reserved.

  • 22.
    Maskenskaya, Olga M.
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Drake, Henrik
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Peltola, Pasi
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Åström, Mats E.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Geochemical variation of fracturecarbonates in crystalline bedrock2011In: Goldschmidt Conference Abstracts 2011. Mineralogical Magazine, Mineralogical Society , 2011, p. 1421-1421Conference paper (Refereed)
  • 23.
    Peng, Bo
    et al.
    Hunan Normal Univ, Peoples Republic of China;Univ Western Australia, Australia.
    Rate, Andrew
    Univ Western Australia, Australia.
    Song, Zhaoliang
    Zhejiang Arg & Forestry Univ, Peoples Republic of China.
    Yu, Changxun
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Hunan Normal Univ, Peoples Republic of China.
    Tang, Xiaoyan
    Hunan Normal Univ, Peoples Republic of China.
    Xie, Shurong
    E China Inst Technol, Peoples Republic of China.
    Tu, Xianglin
    Chinese Acad Sci, Peoples Republic of China.
    Tan, Changyin
    Hunan Normal Univ, Peoples Republic of China.
    Geochemistry of major and trace elements and Pb-Sr isotopes of a weathering profile developed on the Lower Cambrian black shales in central Hunan, China2014In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 51, p. 191-203Article in journal (Refereed)
    Abstract [en]

    This paper reports a geochemical study on the major and trace elements and Pb-Sr isotopes of a weathering profile developed in the Lower Cambrian black shales in central Hunan (China). Six weathering horizons were identified and sampled vertically throughout the profile. The chemical composition of the profile consists of variable concentrations of the major elements Fe2O3, FeO, MnO, MgO, CaO, Na2O, and P2O5 and of less variable concentrations of SiO2, TiO2, Al2O3, and K2O. The chemical change caused by weathering is estimated by mass-balance calculations, and the results show that the element mobility is characterised by substantial loss of SiO2, FeO, CaO, K2O, Na2O, LOI, Cr, V, Ba, Cs, Rb, Sr, U, and Th, and moderate loss of Al2O3, MgO, Fe2O3, Ni, Cu, Pb, Tl, Sn, Sc, Ge and REE (Y). The high field strength elements TiO2, Sn, Sc, U, Ga, Ge, Zr, Hf, Nb, and Ta were immobile during weathering. The chemical changes and the Pb-Sr isotopic data suggest that four types of chemical reactions occurred: the oxidation of sulphide minerals (e.g., pyrite) and organic carbon (OS), the dissolution of less resistant clinochlore-Ia, calcite, and P-bearing minerals (DL), the dissolution of detrital albite and microcline (DA), and the transformation of clay (TC) minerals (e.g., muscovite and illite-smectite). These chemical reactions then led to two stages of geochemical processes, an early stage of chemical differentiation and a later stage of chemical homogenisation. The chemical differentiation dominated by the OS, DL, and DA reactions, led to the leaching of mobile elements (e.g., MgO, Na2O, K2O, P2O5, Sr, and REE) and the redistribution of some less mobile elements (e.g., SiO2 and Al2O3). In contrast, the chemical homogenisation, which was caused by TC reactions, led to the leaching of both mobile and less mobile elements from the system and ultimately transformed the weathered black shales into soil. Soils derived from black shales in South China might result from the above two geochemical processes. (C) 2014 Elsevier Ltd. All rights reserved.

  • 24.
    Yu, Changxun
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Berger, Tobias
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. The Swedish Anglers Association, Sweden.
    Drake, Henrik
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Song, Zhaoliang
    Tianjin University, Peoples Republic of China.
    Peltola, Pasi
    Boliden Rönnskär, Sweden.
    Åström, Mats E.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Geochemical controls on dispersion of U and Th in Quaternary deposits, stream water, and aquatic plants in an area with a granite pluton2019In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 663, p. 16-28Article in journal (Refereed)
    Abstract [en]

    The weathering of U and/or Th rich granite plutons, which occurs worldwide, may serve as a potentially important, but as yet poorly defined source for U and Th in (sub-)surface environments. Here, we assessed the impact of an outcrop of such granite (5 km in diameter) and its erosional products on the distribution of U and Th in four nemo-boreal catchments. The results showed that (i) the pluton was enriched in both U and Th; and (ii) secondary U and Th phases were accumulated by peat/gyttja and in other Quaternary deposits with high contents of organic matter. Movement of the ice sheet during the latest glaciation led to dispersal of U- and Th-rich materials eroded from the pluton, resulting in a progressive increase in dissolved U and Th concentrations, as well as U concentrations in aquatic plants with increasing proximity to the pluton. The accumulation of U in the aquatic plants growing upon the pluton (100–365 mg kg−1, dry ash weight) shows that this rock represents a long-term risk for adjacent ecosystems. Dissolved pools of U and Th were correlated with those of dissolved organic matter (DOM) and were predicted to largely occur as organic complexes. This demonstrates the importance of DOM in the transport of U and Th in the catchments. Large fractions of Ca2UO2(CO3)30(aq) were modeled to occur in the stream with highest pH and alkalinity and thus, explain the strongly elevated U concentrations and fluxes in this particular stream. In future climate scenarios, boreal catchments will experience intensified runoff and warmer temperature that favor the production of hydrologically accessible DOM and alkalinity. Therefore, the results obtained from this study have implications for predicting the distribution and transport of Th and U in boreal catchments, especially those associated with U and/or Th rich granite plutons.

  • 25.
    Yu, Changxun
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Drake, Henrik
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Mathurin, Frédéric A.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Åström, Mats E.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Cerium sequestration and accumulation in fractured crystalline bedrock: The role of Mn-Fe (hydr-)oxides and clay minerals2017In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 199, p. 370-389Article in journal (Refereed)
    Abstract [en]

    This study focuses on the mechanisms of Ce sequestration and accumulation in the fracture network of the upper kilometer of the granitoid bedrock of the Baltic Shield in southeast Sweden (Laxemar area, Sweden). The material includes 81 specimens of bulk secondary mineral precipitates ("fracture coatings") collected on fracture walls identified in 17 drill cores, and 66 groundwater samples collected from 21 deep boreholes with equipment designed for retrieval of representative groundwater at controlled depths. The concentrations of Ce in the fracture coatings, although varying considerably (10-90th percentiles: 67-438 mg kg(-1)), were frequently higher than those of the wall rock (10-90th percentiles: 70-118 mg kg(-1)). Linear combination fitting analysis of Ce L-III-edge X-ray absorption near-edge structure (XANES) spectra, obtained for 19 fracture coatings with relatively high Ce concentrations (>= 145 mg kg(-1)) and a wide range of Ce-anomaly values, revealed that Ce(IV) occurs frequently in the upper 10 m of the fracture network (Ce(IV)/Ce-total = 0.06-1.00 in 8 out of 11 specimens) and is mainly associated with Mn oxides (modeled as Ce oxidatively scavenged by birnessite). These features are in line with the strong oxidative and sorptive capacities of Mn oxide as demonstrated by previous studies, and abundant todorokite and birnessite-like Mn oxides identified in 3 out of 4 specimens analyzed by Mn K-edge X-ray absorption spectroscopy (XAS) in the upper parts of the fracture network (down to 5 m). For a specimen with very high Ce concentration (1430 mg kg(-1)) and NASC-normalized Ce anomaly (3.63), the analysis of Ce XANES and Mn XAS data revealed (i) a predominance of Ce oxide in addition to Ce scavenged by Mn oxide; and (ii) a large fraction of poorly-crystalline hexagonal birnessite and aqueous Mn2+, suggesting a recent or on-going oxidation of Mn2+ in this fracture. In addition, the Ce oxide precipitates on this fracture observed by in situ SEM-EDS contained considerable amounts of Mn. These spectroscopic and microscopic features led us to suggest that the remarkable accumulation of Ce(IV) in this fracture is a result of repeated formation and dissolution of Mn oxides, that is, formation of Mn oxide followed by oxidative scavenging of Ce as Ce oxide nanoparticles, which largely remained during the subsequent reductive dissolution of the Mn oxides. In addition, the XANES data indicate that goethite has the capability to oxidize Ce at near-neutral pH under our experimental conditions (goethite reacted with 0.001M Ce for 48 h in a glove box with O-2 < 1 ppm). This previously unrecognized Ce oxidation pathway also seems to contribute to a minor extent to the oxidative scavenging of Ce in the fracture network. Trivalent Ce in the fracture coatings, in particular below 2.5 m, is mainly sorbed as inner-sphere complexes on clay minerals. Taking into account the facts that Ce in the present groundwater is scarce and modeled to be largely complexed with humic substance, it is argued that the inner-sphere complexes were mainly formed from past (Paleozoic) hydrothermal fluids. (C) 2016 Elsevier Ltd. All rights reserved.

  • 26.
    Yu, Changxun
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Virtasalo, Joonas J.
    Geol Survey Finland GTK, Finland.
    Karlsson, Torbjörn
    Umea Univ.
    Peltola, Pasi
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Osterholm, Peter
    Åbo Akad Univ, Finland.
    Burton, Edward D.
    So Cross Univ, Australia.
    Arppe, Laura
    Univ Helsinki, Finland.
    Hogmalm, Johan K.
    Univ Gothenburg.
    Ojala, Antti E. K.
    Geol Survey Finland GTK, Finland..
    Åström, Mats E.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Iron behavior in a northern estuary: Large pools of non-sulfidized Fe(II) associated with organic matter2015In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 413, p. 73-85Article in journal (Refereed)
    Abstract [en]

    The estuaries of the Northern Baltic Sea (Gulf of Bothnia) receive an abundance of diagenetically reactive catchment-derived Fe, which is to a large degree complexed with organicmatter or present as Fe (hydr-) oxides. However, our understanding of sedimentary Fe diagenesis in these estuaries is limited. To address this limitation, the present study examines Fe geochemistry in a 3.5-m-thick estuarine benthic mud layer and three samples of suspended particulate matter of a catchment on the eastern Gulf of Bothnia. The age-depth model of the mud, constructed on the basis of sedimentary features as well as Cs-137 and aquatic plant C-14 determinations, revealed a high average rate of sedimentation (5 cm . yr(-1)) for the upper mud unit (0-182.5 cm, corresponding to 1973-2011), in response to intensive land-use (ditching) in the catchment since the 1960s and 1970s. The intensive land-use has resulted in a strong increase in the Fe accumulation rates, but has not caused a recognizable impact on the diagenetic processes of Fe including features such as degree of sulfidization and solid-phase partitioning. Iron X-ray absorption spectroscopy (XAS) indicated that in the suspended particulate matter, large proportions (47-58%) of Fe occur as Fe(III)-organic complexes and 2-line ferrihydrite. In the mud, the former is completely reduced, and reactive Fe (defined via extraction with 1 MHCl) was high throughout (52-68%, median = 61%) and strongly dominated by Fe(II). This reactive Fe(II) pool was sulfidized to only a limited extent (degree of reactive sulfidization = 11-26%, median = 17%). This phenomenon is attributed to the brackish-water conditions (i.e. low in sulfate) and the abundant input of reactive Fe(III) from the catchment, leading to a surplus of dissolved Fe2+ over dissolved sulfide in the sediment. The low availability of dissolved sulfide, in combination with the high average sedimentation rate, limits the formation of intermediate reduced sulfur compounds at the water-sediment interface, thereby retarding the conversion of FeS into pyrite (ratios of pyrite-S to AVS = 0.17-1.73, median = 0.37; degree of pyritization = 1-17%, median = 3%). Iron XAS, in combination with wavelet transform analysis, of representative sediment segments from the upper and lower mud units suggests that the non-sulfidized Fe(II) pool is dominantly complexed by organic matter, with the remaining Fe(II) occurring as mackinawite. This has implications for the understanding of early Fe diagenesis in settings with a high input of organic matter and relatively low supply of sulfate. (C) 2015 Elsevier B.V. All rights reserved.

  • 27.
    Yu, Changxun
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Åström, Mats E.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Peltola, Pasi
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Drake, Henrik
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Oxidative weathering of black shale: A long-term humidity cell test2011In: Goldschmidt Conference Abstracts, Mineralogical Society , 2011, p. 2231-2231Conference paper (Refereed)
  • 28.
    Åström, Mats E.
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Österholm, Peter
    Gustafsson, Jon Petter
    Nystrand, Miriam
    Peltola, Pasi
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Nordmyr, Linda
    Boman, Anton
    Attenuation of rare earth elements in a boreal estuary2012In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 96, p. 105-119Article in journal (Refereed)
    Abstract [en]

    This study focuses on attenuation of rare earth elements (REE) when a boreal creek, acidified and loaded with REE and other metals as a result of wetland drainage, empties into a brackish-water estuary (salinity < 6 parts per thousand). Surface water was collected in a transect from the creek mouth to the outer estuary, and settling (particulate) material in sediment traps moored at selected locations in the estuary. Ultrafiltration, high-resolution ICP-MS and modeling were applied on the waters, and a variety of chemical reagents were used to extract metals from the settling material. Aluminium, Fe and REE transported by the acidic creek were extensively removed in the inner/central estuary where the acidic water was neutralised, whereas Mn was relatively persistent in solution and thus redistributed to particles and deposited further down the estuary. The REE removal was caused by several contemporary mechanisms: co-precipitation with oxyhydroxides (mainly Al but also Fe), complexation with flocculating humic substances and sorption to suspended particles. Down estuary the dissolved REE pool, remaining after removal, was fractionated: the < 1 kDa pool became depleted in the middle REE and the colloidal (0.45 mu m-1 kDa) pool depleted in the middle and heavy REE. This fractionation was controlled by the removal process, such that those REE with highest affinity for the settling particles became most depleted in the remaining dissolved pool. Modeling, based on Visual MINTEQ version 3.0 and the Stockholm Humic Model after revision and updating, predicted that the dissolved (< 0.45 mu m) REE pool in the estuary is bound almost entirely to humic substances. Acid sulphate soils, the source of the REE and other metals in the creek water, are widespread on coastal plains worldwide and therefore the REE attenuation patterns and mechanisms identified in the studied estuary are relevant for recognition of similar geochemical processes and conditions in a variety of coastal locations. (C) 2012 Elsevier Ltd. All rights reserved.

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