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  • 151. Dehnert, Andreas
    et al.
    Preusser, Frank
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Evolution of an overdeepened trough in the northern Alpine Foreland at Niederweningen, Switzerland.2012In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457XArticle in journal (Refereed)
    Abstract [en]

    Quaternary deposits in the overdeepened Wehntal, Switzerland, were investigated using both seismicprofiling and the analysis of 93.6 m long drill core using sedimentology, geochemistry, palynology,magnetic properties, and luminescence dating. The sediments reveal evidence for two glacial advancesthat reached the area during Marine Isotope Stage (MIS) 6. The first advance (w185 ka) may have carvedout the basin or at least removed the entire previous Quaternary sediment filling. This first advance likelyreached far beyond the limit of the maximum of the Last Glaciation. The second advance (w140 ka) wasof smaller extent, possibly of cold-based nature, and likely reached only slightly beyond the limits of theLast Glaciation.

  • 152.
    Delcamp, Audray
    et al.
    Department of Geology, Trinity College, Dublin, Dublin 2, Ireland.
    Petronis, M. S.
    Environmental Geology Natural Resource Management Department, New Mexico Highlands University, Las Vegas, New Mexico, 87 701, USA.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Carracedo, Juan Carlos
    Estación Volcanológica de Canarias, IPNA-Consejo Superior de Investigaciones Científicas (CSIC), La Laguna, 38206, Tenerife, Spain.
    van Wyk de Vries, B.
    Laboratoire Magmas et Volcans CNRS-UMR 6524, Observatoire du Physique du Globe de Clermont Université Blaise Pascal, Clermont-Ferrand, France.
    Pérez-Torrado, Francisco José
    Departamento de Física-Geología, Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain.
    Vertical axis rotation of the upper portions of the north-east rift of Tenerife Island inferred from paleomagnetic data2010In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 492, no 1-4, p. 40-59Article in journal (Refereed)
    Abstract [en]

    Paleomagnetic sampling sites were established in 82 dykes along an 8 km long section of the north-east rift-zone (NERZ) of Tenerife, Canary Islands, Spain. Of the 70 interpretable sites, 16 are of normal polarity and 54 of reversed polarity. Four normal polarity sites and fifteen reverse polarity sites were excluded from the grand mean calculation for statistical reasons. After inverting the reverse polarity sites through the origin, the in-situ grand mean yields a declination (D) = 023.8°, an inclination (I) = 42.3°, α95 = 3.2°, ĸ = 39.0, N = 51 that is discordant to the expected late Miocene to Pleistocene field direction (D = 357.6°, I = 38.8°, α95 = 4.7°). This discordance can be explained as either a 26° clockwise vertical axis rotation or a 28° WNW-side-down-tilt about an average 009° horizontal tilt axis. The sampled section is composed of numerous semi-vertical dykes cutting mainly lava flow units that are sub-horizontal and cross-cut by steeply dipping faults (70°–90°). Field evidence is therefore more compatible with a vertical-axis rotation rather than a horizontal axis tilt of the drilled units. We argue that this clockwise vertical-axis rotation is likely related to strike-slip movements that occurred along the edges of the collapse scars and accommodate the emplacement and growth of the underlying intrusive core and associated dykes. Six new 40Ar/39Ar age determinations constrain the main interval of dyke emplacement within the NERZ between 0.99 Ma and 0.56 Ma. The intrusive activity in the sampled section of the rift appears to have been almost continuous, with several intrusion pulses that are probably related to flank destabilisation event(s) during the mid Pleistocene. Our study thus demonstrates a long-lived, multi-faceted history that shaped the NERZ.

  • 153.
    Deng, Hongling
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Mega arrowhead interference pattern in the Central part of the Yanshan Orogenic Belt, North China2014In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 80, p. 25-37Article in journal (Refereed)
    Abstract [en]

    The Chengde-Pingquan region is located in the central part of the Yanshan Orogenic Belt (YOB). At Daheishan and Pingquan in the central YOB, thrusts and folds of variable trends are displayed in 2 km-scale fold interference patterns. Detailed field mapping was conducted to decipher the geometry of these two superimposed structures. Map-view geometry and stereonet plots for outcrop-scale folds indicate that the superimposed structures form arrowhead interference pattern where NW-SE-trending F1 folds are refolded by later ENE-WSW F2 folding. After remove the effects of later faulting, restored map-views of the superimposed structures show that when the F1 folds have inclined axial surfaces but with no an overturned limb, an arrowhead interference pattern (here called modified type-2 pattern) can form. Our field data and reinterpretation of the findings of previous studies suggest that five major shortening phases have occurred in the Chengde-Pingquan region. The first two phases, which formed the superimposed folds, occurred earlier than the Late Triassic (D1) and during the Late Triassic to Early Jurassic (D2). These two phases were followed by three deformation phases that are mainly characterized by thrusting and strike-slip faulting, which strongly modified the large-scale fold interference patterns.

  • 154.
    Denk, Thomas
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Güner, Tuncay H.
    , Istanbul University, Istanbul, Turkey.
    Kvaček, Zlatko
    Charles University, Prague, Czech Republic.
    Bouchal, Johannes M.
    Swedish Museum of Natural History, Department of Paleobiology. johannes.bouchal@nrm.se.
    The early Miocene flora of Güvem (Central Anatolia, Turkey): a window into early Neogene vegetation and environments in the Eastern Mediterranean2017In: Acta Palaeobotanica, ISSN 0001-6594, E-ISSN 1427-6402, Vol. 57, no 2, p. 237-338Article in journal (Refereed)
    Abstract [en]

    The early Burdigalian (MN3) plant assemblage of the Güvem area (northwestern Central Anatolia) is preserved in lacustrine sediments of the Dereköy pyroclastics. Its age is well constrained by radiometric dates of basaltic rocks bracketing the pyroclastics, making the Güvem flora one of the extremely few precisely dated early Miocene floras in the Mediterranean region. The rich assemblage of impression fossils comprises ferns and fern allies (2 species), gymnosperms (12 spp.) and angiosperms (129 spp.). Ilex miodipyrena sp. nov. is described as a new fossil-species. The most diverse families in the assemblage are the Fagaceae with 12 taxa and the Fabaceae with 12 leaf morphotypes and one fruit taxon. Aquatic plants are represented by seven taxa, riparian (including palms) and swamp forest elements by >35 taxa, and lianas by three taxa (Smilax spp., Chaneya). The relatively large number of aquatic and riparian/swamp elements is congruent with the rich fish, amphibian and reptile record of the Güvem area. Another characteristic feature of the plant assemblage is the presence of various lobed leaves which show similarities with modern species of different families (e.g. Alangium, various Malvales). Trees and shrubs growing on well-drained soils and forming closed-canopy and open-canopy forests are the most diversified group (>70 taxa). In terms of number of specimens in the collection and based on field observations, by far the most abundant leaf fossils belong to evergreen oaks of Quercus drymeja and Q. mediterranea and to various types of foliage that cannot be assigned to a particular extant or extinct genus of Fagaceae. These sclerophyllous trees must have covered vast areas surrounding the wetlands that developed during the early Miocene in the Güvem Basin. Based on a recent reassessment of the ecology and taxonomic affinity of these trees, they are considered to reflect humid temperate climatic conditions but with a brief drier season during the winter months. These forests are more similar to the laurel forests of the southeastern United States and those stretching in a narrow belt south of the Himalayas to eastern central China. The large number of Fabaceae may indicate the presence of warm subtropical environments but this is difficult to assess, as they are known for having wide ecological ranges today and in the past. All in all, a larger part of the plant taxa point to forested vegetation. This is in agreement with previous palynological studies which detected only small amounts of herbaceous and grass pollen. Open patches of vegetation may have been restricted to river banks and to rocky areas in a volcanic landscape. The biogeographic patterns detected for the early Miocene of the Güvem assemblage are manifold; most taxa are widespread Northern Hemispheric elements. A substantial part of the species migrated from Asia into Europe during the (late) Paleogene and reached Anatolia during the early Miocene (Fagus, Paliurus, Chaneya, Ailanthus, Quercus kubinyii, Davallia haidingeri, Acer angustilobum, A. palaeosaccharinum). Fewer taxa may have been in Anatolia before they migrated to Europe (e.g. Nerium, Smilax miohavanensis, Quercus sosnowskyi). Finally, very few taxa are Anatolian endemics (e.g. Ilex miodipyrena).

  • 155.
    Dessirier, Benoît
    Stockholms universitet, Institutionen för naturgeografi.
    Numerical modeling of groundwater and air flow between compacted bentonite and fractured crystalline rock2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The geological repository for final storage of spent nuclear fuel, envisioned by the Swedish Nuclear Fuel and Management Company (SKB), relies on several barriers: copper canisters deposited in holes in the floor of underground tunnels in deep bedrock, embedded in a buffer of compacted bentonite. The initially unsaturated buffer would take up water from the surrounding rock mass and swell to seal any potential gap. This initial two-phase (gas and liquid) regime with two components (air and water) may impact the final density, swelling pressure and biogeochemical conditions in the buffer. A main objective of this work is to identify factors and mechanisms that govern deposition hole inflow and bentonite wetting under the prevailing two-phase flow conditions in sparsely fractured bedrock. For this purpose, we use the numerical code TOUGH2 to perform two-phase flow simulations, conditioned by a companion field experiment (the Bentonite Rock Interaction Experiment or BRIE) performed in a 417 m deep tunnel of the Äspö Hard Rock Laboratory in southeastern Sweden. The models predict a significant de-saturation of the rock wall, which was confirmed by field data. To predict the early buffer wetting rates and patterns, the position of local flowing fractures and estimates of local rock matrix permeability appear more important than the total open hole groundwater inflow. A global sensitivity analysis showed that the buffer wetting time and the persistence of unsaturated conditions over extended periods of time in the rock depend primarily on the local fracture positions, rock matrix permeability, ventilation conditions in the tunnel and pressure far in the rock. Dismantling photographs from BRIE were used to reconstruct a fine-scale snapshot of saturation at the bentonite/rock interface, showing tremendous spatial variability. The high level of heterogeneity in the rock generates complex two-phase flow phenomena (air trapping, dissolution), which need to be accounted for in buffer design and rock suitability criteria. In particular, results suggest that uncertainties regarding two-phase flow behavior are relatively high close to residual air saturation, which may also have important implications for other applications involving two-phase flows, such as geological storage of carbon dioxide.

  • 156.
    Dessirier, Benoît
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Numerical modeling of groundwater and air flow between compacted bentonite and fractured crystalline rock2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The geological repository for final storage of spent nuclear fuel, envisioned by the Swedish Nuclear Fuel and Management Company (SKB), relies on several barriers: copper canisters deposited in holes in the floor of underground tunnels in deep bedrock, embedded in a buffer of compacted bentonite. The initially unsaturated buffer would take up water from the surrounding rock mass and swell to seal any potential gap. This initial two-phase (gas and liquid) regime with two components (air and water) may impact the final density, swelling pressure and biogeochemical conditions in the buffer. A main objective of this work is to identify factors and mechanisms that govern deposition hole inflow and bentonite wetting under the prevailing two-phase flow conditions in sparsely fractured bedrock. For this purpose, we use the numerical code TOUGH2 to perform two-phase flow simulations, conditioned by a companion field experiment (the Bentonite Rock Interaction Experiment or BRIE) performed in a 417 m deep tunnel of the Äspö Hard Rock Laboratory in southeastern Sweden. The models predict a significant de-saturation of the rock wall, which was confirmed by field data. To predict the early buffer wetting rates and patterns, the position of local flowing fractures and estimates of local rock matrix permeability appear more important than the total open hole groundwater inflow. A global sensitivity analysis showed that the buffer wetting time and the persistence of unsaturated conditions over extended periods of time in the rock depend primarily on the local fracture positions, rock matrix permeability, ventilation conditions in the tunnel and pressure far in the rock. Dismantling photographs from BRIE were used to reconstruct a fine-scale snapshot of saturation at the bentonite/rock interface, showing tremendous spatial variability. The high level of heterogeneity in the rock generates complex two-phase flow phenomena (air trapping, dissolution), which need to be accounted for in buffer design and rock suitability criteria. In particular, results suggest that uncertainties regarding two-phase flow behavior are relatively high close to residual air saturation, which may also have important implications for other applications involving two-phase flows, such as geological storage of carbon dioxide.

  • 157.
    Dessirier, Benoît
    et al.
    Stockholms universitet, Institutionen för naturgeografi, Stockholm, Sweden..
    Frampton, Andrew
    Stockholms universitet, Institutionen för naturgeografi.
    Jarsjö, Jerker
    Stockholms universitet, Institutionen för naturgeografi.
    A global sensitivity analysis of two-phase flow between fractured crystalline rock and bentonite with application to spent nuclear fuel disposal2015In: Journal of Contaminant Hydrology, ISSN 0169-7722, E-ISSN 1873-6009, Vol. 182, p. 25-35Article in journal (Refereed)
    Abstract [en]

    Geological disposal of spent nuclear fuel in deep crystalline rock is investigated as a possible long term solution in Sweden and Finland. The fuel rods would be cased in copper canisters and deposited in vertical holes in the floor of deep underground tunnels, embedded within an engineered bentonite buffer. Recent experiments at the Äspö Hard Rock Laboratory (Sweden) showed that the high suction of unsaturated bentonite causes a de-saturation of the adjacent rock at the time of installation, which was also independently predicted in model experiments. Remaining air can affect the flow patterns and alter bio-geochemical conditions, influencing for instance the transport of radionuclides in the case of canister failure. However, thus far, observations and model realizations are limited in number and do not capture the conceivable range and combination of parameter values and boundary conditions that are relevant for the thousands of deposition holes envisioned in an operational final repository.

    In order to decrease this knowledge gap, we introduce here a formalized, systematic and fully integrated approach to study the combined impact of multiple factors on air saturation and dissolution predictions, investigating the impact of variability in parameter values, geometry and boundary conditions on bentonite buffer saturation times and on occurrences of rock de-saturation. Results showed that four parameters consistently appear in the top six influential factors for all considered output (target) variables: the position of the fracture intersecting the deposition hole, the background rock permeability, the suction representing the relative humidity in the open tunnel and the far field pressure value. The combined influence of these compared to the other parameters increases as one targets a larger fraction of the buffer reaching near-saturation. Strong interaction effects were found, which means that some parameter combinations yielded results (e.g., time to saturation) far outside the range of results obtained by the rest of the scenarios. This study also addresses potential air trapping by dissolution of part of the initial air content of the bentonite, showing that neglecting gas flow effects and trapping could lead to significant underestimation of the remaining air content and the duration of the initial aerobic phase of the repository.

  • 158.
    Dessirier, Benoît
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Frampton, Andrew
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    A global sensitivity analysis of two-phase flow between fractured crystalline rock and bentonite with application to spent nuclear fuel disposal2015In: Journal of Contaminant Hydrology, ISSN 0169-7722, E-ISSN 1873-6009, Vol. 182, p. 25-35Article in journal (Refereed)
    Abstract [en]

    Geological disposal of spent nuclear fuel in deep crystalline rock is investigated as a possible long term solution in Sweden and Finland. The fuel rods would be cased in copper canisters and deposited in vertical holes in the floor of deep underground tunnels, embedded within an engineered bentonite buffer. Recent experiments at the Äspö Hard Rock Laboratory (Sweden) showed that the high suction of unsaturated bentonite causes a de-saturation of the adjacent rock at the time of installation, which was also independently predicted in model experiments. Remaining air can affect the flow patterns and alter bio-geochemical conditions, influencing for instance the transport of radionuclides in the case of canister failure. However, thus far, observations and model realizations are limited in number and do not capture the conceivable range and combination of parameter values and boundary conditions that are relevant for the thousands of deposition holes envisioned in an operational final repository.

    In order to decrease this knowledge gap, we introduce here a formalized, systematic and fully integrated approach to study the combined impact of multiple factors on air saturation and dissolution predictions, investigating the impact of variability in parameter values, geometry and boundary conditions on bentonite buffer saturation times and on occurrences of rock de-saturation. Results showed that four parameters consistently appear in the top six influential factors for all considered output (target) variables: the position of the fracture intersecting the deposition hole, the background rock permeability, the suction representing the relative humidity in the open tunnel and the far field pressure value. The combined influence of these compared to the other parameters increases as one targets a larger fraction of the buffer reaching near-saturation. Strong interaction effects were found, which means that some parameter combinations yielded results (e.g., time to saturation) far outside the range of results obtained by the rest of the scenarios. This study also addresses potential air trapping by dissolution of part of the initial air content of the bentonite, showing that neglecting gas flow effects and trapping could lead to significant underestimation of the remaining air content and the duration of the initial aerobic phase of the repository.

  • 159.
    Dessirier, Benoît
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Frampton, Andrew
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Impact of near-wall rock characteristics on bentonite buffer wetting: In situ study of nuclear fuel deposition holes in deep bedrockManuscript (preprint) (Other academic)
  • 160.
    Dessirier, Benoît
    et al.
    Department of Physical Geography, Stockholm University, Sweden..
    Åkesson, Mattias
    Clay Technol AB, IDEON Sci Pk, S-22370 Lund, Sweden.
    Lanyon, Bill
    Fracture Syst Ltd, St Ives, England.
    Frampton, Andrew
    Stockholm Univ, Dept Phys Geog, S-10691 Stockholm, Sweden.
    Jarsjö, Jerker
    Stockholm Univ, Dept Phys Geog, S-10691 Stockholm, Sweden.
    Reconstruction of the water content at an interface between compacted bentonite blocks and fractured crystalline bedrock2017In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 142, p. 145-152Article in journal (Refereed)
    Abstract [en]

    High-density sodium bentonite combines a low permeability with a swelling behavior, which constitute two important qualities for engineered barriers in geological disposal of spent nuclear fuel. For example, the KBS-3V method developed in Sweden and Finland is planned to include compacted bentonite as the buffer material to embed canisters containing the spent nuclear fuel packages in deposition holes in deep crystalline bedrock. The partially saturated bentonite buffer will then swell as it takes up groundwater from the surrounding rock. It is important to quantify the water content evolution of the installed buffer to correctly predict the development of the swelling pressure and the prevailing conditions (thermal, mechanical, chemical and biological). This study aimed at quantifying the water content profile at the surface of a cylindrical bentonite parcel retrieved after in situ wetting in fractured crystalline bedrock. We demonstrate the possibility of using regression-kriging to quantitatively include spatial information from high-resolution photographs of the retrieved bentonite parcel, where more water saturated areas appear as relatively dark shades, along with bentonite samples, where detailed measurements of water content were performed. The resulting reconstruction is both exact regarding local sample measurements and successful to reproduce features such as intersecting rock fracture traces, visible in the photographs. This level of detail is a key step to gain a deeper understanding of the hydraulic behavior of compacted bentonite barriers in sparsely fractured rock. An improved scanning procedure could further increase the accuracy by reducing errors introduced by the geometrical transformations needed to unfold and stitch the different photographs into a single gray scale map of the bentonite surface. The application of this technique could provide more insights to ongoing and planned experiments with unsaturated bentonite buffers.

  • 161.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Modeling and uncertainty assessment of nutrient runoff from larger catchments2011In: International Seminar on Pollution runoff from urban and non-urban catchments, Technical University of Denmark (DTU), Copenhagen, March 30, 2011., 2011Conference paper (Other academic)
  • 162.
    Dingwell, Adam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Rutgersson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Estimating volcanic ash hazard in European airspace2014In: Journal of Volcanology and Geothermal Research, ISSN 0377-0273, E-ISSN 1872-6097, Vol. 286, p. 55-66Article in journal (Refereed)
    Abstract [en]

    The widespread disruption of European air traffic in late April 2010, during the eruption of Eyjafjallajökull,showed the importance of early assessment of volcanic hazard from explosive eruptions. In this study, wefocus on the short-term hazard of airborne ash from a climatological perspective, focusing on eruptions onIceland. By studying eruptions of different intensity and frequency, we estimate the overall probability that ashconcentration levels considered hazardous to aviation are exceeded over different parts of Europe.

    The method involves setting up a range of eruption scenarios based on the eruptive history of Icelandic volcanoes,and repeated simulation of these scenarios for 2 years' worth of meteorological data. Simulations are conducted using meteorological data from the ERA-Interim reanalysis set, which is downscaled using the Weather Researchand Forecasting (WRF) model. The weather data are then used to drive the Lagrangian particle dispersion model FLEXPART-WRF for each of the eruption scenarios. A set of threshold values, commonly used in Volcanic Ash Advisories, are used to analyze concentration data from the dispersion model.

    We see that the dispersion of ash is highly dominated by the mid-latitude westerlies and mainly affect northern UK and the Scandinavian peninsula. The occurrence of high ash levels from Icelandic volcanoes is lower over con-tinental Europe but should not be neglected for eruptions when the release rate of fine ash (<16 μm) is in theorder of 107 kg s−1 or higher.

    There is a clear seasonal variation in the ash hazard. During the summer months, the dominating dispersiondirection is less distinct with some plumes extending to the northwest and Greenland. In contrast, during thewinter months, the strong westerly winds tend to transport most of the emissions eastwards. The affected area of a winter-time eruption is likely to be larger as high concentrations can be found at a further distance downwind from the volcano, effectively increasing the probability of hazardous levels of ash reaching the European continent.

    The concentration thresholds for aviation, which were adopted after the Eyjafjallajökull eruption in 2010, havestrong influence on the hazard estimates for weaker eruptions but is less important for larger eruptions; thusash forecasts for weaker eruptions are likely more uncertain in comparison to larger eruptions.

  • 163.
    Dong, Fang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Moving Object Trajectory Based Spatio-Temporal Mobility Prediction.2012Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
  • 164.
    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

  • 165.
    Earon, Robert
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Dehkordi, Seyed Emad
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Olofsson, Bo
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Groundwater Resources Potential in Hard Rock Terrain: A Multivariate Approach2014In: Ground Water, ISSN 0017-467X, E-ISSN 1745-6584Article in journal (Refereed)
    Abstract [en]

    Groundwater resources are limited and difficult to predict in crystalline bedrock due to heterogeneity and anisotropy in rock fracture systems. Municipal-level governments often lack the resources for traditional hydrogeological tests when planning for sustainable use of water resources. A new methodology for assessing groundwater resources potential (GRP) based on geological and topographical factors using principal component analysis (PCA) and analysis of variance (ANOVA) was developed and tested. ANOVA results demonstrated statistically significant differences in classed variable groups as well as in classed GRP scores with regard to hydrogeological indicators, such as specific capacity (SC) and transmissivity. Results of PCA were used to govern the weight of the variables used in the prediction maps. GRP scores were able to identify 79% of wells in a verification dataset, which had SC values less than the total dataset median. GRP values showed statistically significant correlations using both parametric (using transformed datasets) and non-parametric methods. The method shows promise for municipal or regional level planning in crystalline terrains with high levels of heterogeneity and anisotropy as a hydrogeologically and statistically based tool to assist in assessing groundwater resources. The methodology is executed in a geographic information systems environment, and uses often readily available data, such as geological maps, feature maps and topography, and thus does not require expensive and time-consuming aquifer tests.

  • 166.
    Ebbestad, Jan Ove R.
    et al.
    Uppsala University, Music and Museums, Museum of Evolution.
    Weidner, Thomas
    Ravnholtvej 23, DK-7130 Juelsminde, Denmark..
    Extreme Protomeric Development In A Burlingiid Trilobite From Cambrian Glacial Erratics Of Denmark2017In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 60, no 2, p. 233-253Article in journal (Refereed)
    Abstract [en]

    Pengia Geyer & Corbacho is a Cambrian burlingiid trilobite with fused trunk segments devoid of any articulation in the anamorphic and epimorphic phases of development. The type species is Pengia fusilis (Peng etal.) from the Wanshania wanshanensis Zone of China. Here we describe a second species, Pengia palsgaardia sp. nov., from the Lejopyge laevigata Zone of the Paradoxides forchhammeri Superzone. It comes from a glacial erratic in Denmark which probably originated in the Alum Shale Formation of Vastergotland, Sweden. Pengia palsgaardia is a large burlingiid (similar to 10mm in length), with 14 fused segments in the trunk whose boundaries are marked by ridges. The axis is narrow, with the axial furrows faintly indicated or effaced across the median. Laterally along the axis and the tapering glabella, symmetrical globular lobes are developed that are pinched at their base. During ontogeny the glabellar furrows are pit-like adaxially but shallow towards the axial furrow as the globular lobes develop. Their pit-like appearance in Pengia palsgaardia and some other burlingiid species is not considered similar to the condition seen in oryctocephalid trilobites. A median preglabellar ridge resembling that of Schmalenseeia Moberg develops late in ontogeny but in early ontogeny the preglabellar field resembles that of Burlingia Walcott, Alumenella Geyer & Corbacho and Niordilobites Geyer & Corbacho. This gives Pengia a more basal position in the schmalenseeid lineage, outside the derived Schmalenseeia. In mature specimens the facial sutures in P.palsgaardia are fused, but an ocular suture may have been present. During ontogeny Pengia would have gone through the anamorphic and protomeric protaspid segmental conditions, but articulation between either the cephalon and pygidium, or pygidium and thoracic segments of the trunk never developed so it did not progress beyond the protaspid phase. This extreme protomeric development is considered to be a derived feature in Pengia.

  • 167.
    Edberg, Elin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Environmental Development around Falun Copper Mineduring Late Holocene2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The area at and around the Falun copper mine has always been of great interest. To begin with it was the valuable ore that drew people to the area. Now it is the historical, archaeological and environmental aspects that draw researchers from different fields of study to Falun. Peat cores were taken in several peatlands throughout an area extending toward about 2 kilometres to the west, southwest and south of the Falun mine. One core was selected for more extensive studies including plant macrofossil analysis, loss on ignition (LOI) and 14C – analysis. These methods are combined to give a picture of the environmental conditions at different periods in time, using plants and their preferred growth environment as an aid. The untouched environment changing into the well-known mining landscape that prevailed in the hey-day of the mine, with the change being the focal point, is the reason for this study.The cores presented in this thesis generally show lake areas drying up and transforming into peatlands, some peatlands may however have been formed in other ways. The location chosen for further studies is now almost transformed to a forest floor. This study provides a solid foundation for further studies as well as adds more information to existing knowledge. However, more research is needed to fully understand how the environment changed due to the opening of the mine.

  • 168.
    Ekeberg, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Swedish Institute of Space Physics, P.O. Box 812, SE-981 28 Kiruna, Sweden.
    Wannberg, Gudmund
    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.
    Häggström, Ingemar
    EISCAT Scientific Association, P.O. Box 812, SE-981 28 Kiruna, Sweden.
    Soliton-induced spectrally uniform ion line power enhancements at the ionospheric F region peak2012In: Earth Planets and Space, ISSN 1343-8832, E-ISSN 1880-5981, Vol. 64, no 7, p. 605-611Article in journal (Refereed)
    Abstract [en]

    We present European incoherent scatter (EISCAT) observations of spectrally uniform ion line power enhancements (SUIPE), where the up- and downshifted shoulder and the spectral valley between them are enhanced simultaneously and equally. We have identified 48 cases of this type of ion line enhancements in data from the EISCAT Svalbard radar taken during the International Polar Year (extending from March 2007 to the end of February 2008). The SUIPEs are observed at altitudes between 210 km and 280 km with a standard deviation of 9% of the average occurrence height 230 km. The power enhancements are one order of magnitude above the thermal level. The SUIPEs occur at the ionospheric F region peak with 85% of the cases located within 10 km of the peak. The occurrence shows a clear preference for magnetically disturbed conditions, with the likelihood of occurrence increasing with increasing K index. A majority of the events occur in the magnetic evening to pre-midnight sector.

  • 169.
    Eklund, Carl
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ståndortsfaktorer och vegetation: En problematiserande litteraturstudie2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A site is an area where a population of a specific plant species has its habitat, often the connotation is forestry. The prerequisites for this, the site indices (also site variables or stand variables), can be found in the characteristics of the ground (edaphic factors) as well as the climatic impact. These elements affect the growth and production, which is of interest in forestry and forest sciences. Upon this the plants interact with each other as well as with other organisms, i.e. fungi, bacteria and animals, and there is also an anthropogenic impact where factors such as livestock grazing, atmospheric deposition and forest production strongly affects the vegetation.

    By studying some of the more prominent theories on vegetation societies/sociologies and plant strategies, as well as different aspects of the site concept, the hypothesis was that a problematizing picture of site indices can be found and some confounding variables that can give erroneous interpretation of results.

    A number of major works in vegetation classification was gone through, supplemented by supporting literature. An article search was conducted to find journal articles, using combinations of specific search terms related to site indices. To narrow down the results and give a more regional touch to the thesis, the filter was set only to show results from Scandinavia and Finland. The articles were grouped into themes and handled theme-wise.

    Even though there are few principal factors controlling the vegetation there are a number of variables which locally can have a large impact, such as snow, genetic traits and symbiosis. These variables can be hard to measure, and a lot of things at a detailed level are poorly investigated. Land use modifies the edaphic properties long after the usage have changed or been discontinued. The amounts and cycles of nitrogen and carbon are recurrent uncertainties in the articles, where deposits of nitrogen from the atmosphere plays an important but uneven role and measurements can be hard to compare due to differences in weather and climate. Added to this, organisms in the ground have a major role in the plants’ nutrient uptake, but the effects can be hard to study. A concluding remark is that even though all aspects of a site cannot always be included more confounding variables could be taken in account and models should be able to be calibrated to different theories on vegetation societies/sociologies and plant strategies. Many factors normally not counted as site indices, i.e. snow depth, soil biota symbiosis, and land use, could be valuable to include in e.g. modelling. 

  • 170.
    Eliassen, Nicole
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Cell Size Variation in Fossil Coccolithophores (Haptophyta): A Study of Pliocene Sediments from Northwestern Australia2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report examines the size variations of fossil carbonate-producing haptophyte microalgae, coccolithophores, using sediments deposited during the Pliocene. The sediments were collected by the International Ocean Discovery Program (IODP) in 2015, off the coast of NW Australia (Gallagher et al., 2017). A climate shift from arid to humid, warm climate occurred over northwest Australia during the early Pliocene, leading to the so-called “Humid Interval” 5.5-3.3 Ma (Christensen et al., 2017). The investigated samples cover approximately 1 million years within this Humid Interval (~4.5 to 3.5 million years ago, Ma).

    The cell size of coccolithophores can be related to growth and carbonate production rates, and thus size becomes important to examine as these marine algae are considered to be a big part of the carbon cycle. Previous laboratory work has shown that environmental factors such as temperature, nutrient availability, and pH affect extant coccolithophore cell size. By looking at reports concerning related extant species, such as Emiliania huxleyi, clues can be given as to why the fossil genusReticulofenestra may have changed in cell size during the Pliocene.

    The measurements of fossil Reticulofenestra coccospheres in this report show an increase in cell size during the studied interval that could be due to heat stress, limited nutrient availability, or other factors, that are less beneficial for the growth of coccolithophores.

  • 171.
    Engel, Fabian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Farrell, Kaitlin J.
    McCullough, Ian M.
    Scordo, Facundo
    Denfeld, Blaize A.
    Dugan, Hilary A.
    de Eyto, Elvira
    Hanson, Paul C.
    McClure, Ryan P.
    Nõges, Peeter
    Nõges, Tiina
    Ryder, Elizabeth
    Weathers, Kathleen C.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    A lake classification concept for a more accurate global estimate of the dissolved inorganic carbon export from terrestrial ecosystems to inland waters2018In: The Science of Nature: Naturwissenschaften, ISSN 0028-1042, E-ISSN 1432-1904, Vol. 105, no 3, article id 25Article in journal (Refereed)
    Abstract [en]

    The magnitude of lateral dissolved inorganic carbon (DIC) export from terrestrial ecosystems to inland waters strongly influences the estimate of the global terrestrial carbon dioxide (CO2) sink. At present, no reliable number of this export is available, and the few studies estimating the lateral DIC export assume that all lakes on Earth function similarly. However, lakes can function along a continuum from passive carbon transporters (passive open channels) to highly active carbon transformers with efficient in-lake CO2 production and loss. We developed and applied a conceptual model to demonstrate how the assumed function of lakes in carbon cycling can affect calculations of the global lateral DIC export from terrestrial ecosystems to inland waters. Using global data on in-lake CO2 production by mineralization as well as CO2 loss by emission, primary production, and carbonate precipitation in lakes, we estimated that the global lateral DIC export can lie within the range of 0.70(-0.31)(+0.27) 1.52(-0.90)(+1.09) Pg C yr(-1) depending on the assumed function of lakes. Thus, the considered lake function has a large effect on the calculated lateral DIC export from terrestrial ecosystems to inland waters. We conclude that more robust estimates of CO2 sinks and sources will require the classification of lakes into their predominant function. This functional lake classification concept becomes particularly important for the estimation of future CO2 sinks and sources, since in-lake carbon transformation is predicted to be altered with climate change.

  • 172.
    Engelhardt, Felix
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Creating an Environmental Geographic Information System for the City of Kumasi, Ghana2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The city of Kumasi in Ghana struggles with a number of environmental issues, including excessive road traffic, air and water pollution, flooding, and inadequate solid waste management. If there is a group that is directly affected by these issues, it certainly is the city’s population. At the same time, the people of Kumasi—who are the constituents of the local administration, called KMA—have few to none means of obtaining objective information about the state of the urban environment, and therefore no way of holding the city administration accountable concerning environmentally relevant decisions. This case study aims to explore the possibility of alleviating this transparency issue by creating an ‘environmental information system’ (EIS) for the city. The term EIS in this context denotes an information system which can be used to publish environmental information on the web, to be utilised by students, professionals, NGOs, and the general public. The case study seeks to provide answers to two research questions: What are the software requirements for an EIS for Kumasi? And: How can free software be used to satisfy these requirements? The case study takes an approach based on Soft Systems Methodology and agile software development techniques to explore the software requirements. As part of the study, a prototype of the EIS was developed in order to explore the requirements even more, and in order to determine the applicability of currently available free software.

    The results of the requirements analysis include the following observations: geographical information is essential in presenting the city’s environmental issues, therefore the EIS is based on geographic information system (GIS) software and techniques; the information should be presented to the public in an easy-to-use and easy-to-understand way in order to reach the largest possible percentage of the target group; the environmental information that is available at local institutions (such as the largest local university KNUST, the city administration, and the Environmental Protection Agency) is scarce and semantically and syntactically heterogeneous—therefore, the EIS must be able to consolidate such information in order to present it in an easy-to-understand way; many of the involved actors have no or little knowledge in GIS techniques, therefore the EIS must be usable without such knowledge. In the implementation process, heavy use was made of free software components: GeoServer for publishing geographical data using WMS and WFS; PostgreSQL with the PostGIS extension for data storage; JPA/Hibernate for storing metadata in PostgreSQL; Spring MVC, jQuery UI and many other libraries for creating a user-friendly web application; OpenLayers for displaying and editing geographical data in the web application; GeoTools for handling geographical data on the server-side. During implementation, actual environmental information was entered into the EIS in order to provide a realistic semantic environment for the agile development process.

    The study concludes that—while the implemented prototype does not include all of the features which were identified as required, and while a ‘full’ soft systems analysis (as opposed to the ‘soft systems perspective’ which was applied) would have led to a more complete picture of the software’s organisational environment—the implementation of an environmental information system for Kumasi, based solely on free software, is viable in the current technical and organisational environment. KNUST is foreseen to be an adequate organisation to manage the development and operation of the system, since the necessary technical knowledge is available. The successful operation of the EIS relies on environmental information being provided by data producers such as the KMA, the EPA, the Ghana Statistical Service, and various departments at KNUST.

  • 173.
    Eriksson, Therese
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Naturkatastrofer i Sverige2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    To be able to plan and construct a Swedish society that is well prepared for geological hazards, the government need to know about past event that has happened during the history, so they know how to plan for the future. Highly possible events that will happen are flooding, landslides, volcanic gases in the atmosphere and earthquakes. Flooding is the hazard that we need to consider most when we construct new infrastructure and buildings in the future. Climate changes will cause more precipitation and extreme weather, these will lead to more flooding when the water isn’t able to percolate down into the ground. When the ground is saturated with water another problem will be even more common, and that is a bigger frequency of landslides. The most dramatic consequence that would occur is from volcanic gases that go up into the atmosphere at an eruption, these can change the climate and create acid rain far away from the volcanic source. It isn’t just the direct hazards we need to consider while constructing the society, the question regarding nuclear waste and its long-term storage is highly important. Therefore is it very important to carefully consider where, and when big earthquakes have occurred since the last glaciation. 

  • 174.
    Eshagh, Mehdi
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Bi-Objective models of Geodetic Network Optimization2006Conference paper (Refereed)
  • 175.
    Eshagh, Mehdi
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Multi-Objective Models of Geodetic Network Optimization2006Conference paper (Refereed)
  • 176.
    Eshagh, Mehdi
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Orbit integration in non-inertial frame2009In: Journal of the Earth and Space Physics, ISSN 0378-1046, Vol. 35, no 1, p. 1-8Article in journal (Refereed)
  • 177.
    Eshagh, Mehdi
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Scalar Risk functions as Criteria for datum Definition of Geodetic Networks2006Conference paper (Refereed)
  • 178.
    Eshagh, Mehdi
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Sequential Tikhonov Regularization: an alternative way for inverting satellite gradiometric data2011In: Zfv, ISSN 1618-8950, Vol. 136, no 2, p. 113-121Article in journal (Refereed)
    Abstract [en]

    Numerous regularization methods exist for solving the ill-posed problem of downward continuation of satellite gravity gradiometry (SGG) data to gravity anomaly at sea level. Generally, the use of a dense set of data is recommended in the downward continuation. However, when such dense data are used some of the regularization methods are not efficient and applicable. In this paper, a sequential way of using the Tikhonov regularization is developed for solving large systems and compared to methods of direct truncated singular value decomposition and iterative methods of range restricted minimum residual, algebraic reconstruction technique,  and conjugate gradient for recovering gravity anomaly at sea level from the SGG data. Numerical studies show that the sequential Tikhonov regularization is comparable to the conjugate gradient and yields similar result.

     

  • 179.
    Eshagh, Mehdi
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Geodesy (closed 20110301).
    The Effect of Polar Gaps on the Solutions of Gradiometric Boundary Value Problems2008In: Artificial Satellites, ISSN 0208-841X, Vol. 43, no 3, p. 97-108Article in journal (Refereed)
    Abstract [en]

    The lack of satellite gravity gradiometric data, due to inclined orbit, in the Polar Regions influences the geopotential coefficients obtained from the solutions of gradiometric boundary value problems. This paper investigates the polar gaps effect on these solutions and it presents that the near zero-, first- and second-order geopotential coefficients are weakly determined by the vertical-vertical, vertical-horizontal and horizontal solutions, respectively. Also it shows that the vertical-horizontal solution is more sensitive to the lack of data than the other solutions.

  • 180.
    Eshagh, Mehdi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Najafi-Alamdari, Mehdi
    Investigation of Orbital Perturbations of a Low Earth Orbiting (LEO) Satellite2005Conference paper (Refereed)
  • 181.
    Eshagh, Mehdi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Najafi-Alamdari, Mehdi
    KNToosi University of Technology.
    Numerical Orbit Integration of a Low earth Orbiting satellite2005Conference paper (Other academic)
  • 182.
    Eshagh, Mehdi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Najafi-Alamdari, Mehdi
    KNToosi University of Technology.
    Farnin, Ahmed
    Islamic Azad University.
    Investigation of long wavelength EIGEN spheroids of Iran2006Conference paper (Refereed)
  • 183.
    Eshagh, Mehdi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Romeshkani, Mohsen
    Department of Geodesy, KNToosi Uni. Tech..
    Generation of vertical–horizontal and horizontal–horizontal gravity gradients using stochastically modified integral estimators2011In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 48, no 8, p. 1341-1358Article in journal (Refereed)
    Abstract [en]

    The Earth’s gravity field modelling is an ill-posed problem having a sensitive solution to the error of data. Satellite gravity gradiometry (SGG) is a space technique to measure the second-order derivatives of geopotential for modelling this field, but the measurements should be validated prior to use. The existing terrestrial gravity anomalies and Earth gravity models can be used for this purpose. In this paper, the second-order vertical–horizontal (VH) and horizontal–horizontal (HH) derivatives of the extended Stokes formula in the local north-oriented frame are modified using biased, unbiased and optimum types of least-squares modification. These modified integral estimators are used to generate the VH and HH gradients at 250 km level for validation purpose of the SGG data. It is shown that, unlike the integral estimator for generating the second-order radial derivative of geopotential, the system of equations from which the modification parameters are obtained is unstable for all types of modification, with large cap size and high degree, and regularization is strongly required for solving the system. Numerical studies in Fennoscandia show that the SGG data can be estimated with an accuracy of 1 mE using an integral estimator modified by a biased type least-squares modification. In this case an integration cap size of 2.5° and a degree of modification of 100 for integrating 30′ × 30′ gravity anomalies are required.

  • 184.
    Eshagh, Mehdi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Sjöberg, Lars E.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Satellite Gravity Gradiometry: An approch to high resolution gravity field modelling from space2009Book (Other academic)
  • 185.
    Evans, Chris D.
    et al.
    Ctr Ecol & Hydrol, Deiniol Rd, Bangor LL57 2UW, Gwynedd, Wales.; Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Lennart Hjalms Vag 9, S-75007 Uppsala, Sweden.
    Futter, Martyn N.
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Lennart Hjalms Vag 9, S-75007 Uppsala, Sweden.
    Moldan, Filip
    IVL Swedish Environm Res Inst, POB 5302, S-40014 Gothenburg, Sweden.
    Valinia, Salar
    Norwegian Inst Water Res, Gaustadalleen 21, N-0349 Oslo, Norway.; Swedish Environm Protect Agcy, Valhallavagen 195, S-10648 Stockholm, Sweden.
    Frogbrook, Zoe
    Scottish Water, 55 Buckstone Terrace, Edinburgh EH10 6XH, Midlothian, Scotland.
    Kothawala, Dolly
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Variability in organic carbon reactivity across lake residence time and trophic gradients2017In: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 10, no 11, p. 832-835Article in journal (Refereed)
    Abstract [en]

    The transport of dissolved organic carbon from land to ocean is a large dynamic component of the global carbon cycle. Inland waters are hotspots for organic matter turnover, via both biological and photochemical processes, and mediate carbon transfer between land, oceans and atmosphere. However, predicting dissolved organic carbon reactivity remains problematic. Here we present in situ dissolved organic carbon budget data from 82 predominantly European and North American water bodies with varying nutrient concentrations and water residence times ranging from one week to 700 years. We find that trophic status strongly regulates whether water bodies act as net dissolved organic carbon sources or sinks, and that rates of both dissolved organic carbon production and consumption can be predicted from water residence time. Our results suggest a dominant role of rapid light-driven removal in water bodies with a short water residence time, whereas in water bodies with longer residence times, slower biotic production and consumption processes are dominant and counterbalance one another. Eutrophication caused lakes to transition from sinks to sources of dissolved organic carbon. We conclude that rates and locations of dissolved organic carbon processing and associated CO2 emissions in inland waters may be misrepresented in global carbon budgets if temporal and spatial reactivity gradients are not accounted for.

  • 186.
    Evers, Mariele
    et al.
    University of Bonn , Germany.
    Nyberg, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Centre for Climate and Safety.
    Coherence and inconsistency of European instruments for integrated river basin management2013In: International Journal of River Basin Management, ISSN 1571-5124, E-ISSN 1814-2060, Vol. 11, p. 139-152Article in journal (Refereed)
    Abstract [en]

    Large rivers are particularly under pressure due to multiple uses which often have severe impacts on ecosystems, or water quality and flow. Conflicting aims and a lack of integration and cooperation in planning and management are not beneficial to sustainable management. Important elements of integrated river basin management (IRBM) include both water quality aspects and floodplain and flood risk management. On the other hand, land use and land use planning are also both of great importance for sustainable river management. However, water management and land use planning are generally treated as two distinct issues in planning procedures and decision-making processes. Even water quality and flood risk issues are often handled by different authorities. Integrated management of transnational river basins is even more complicated and difficult. In Europe, there is a range of relevant Directives such as the Water Framework Directive, Floods Directive and Habitat Directive. This paper illustrates how these legal and planning instruments influence the IRBM of large rivers. It analyses the potential synergies of the goals outlined in the directives and various related measures. Coherent but also inconsistent aspects of IRBM are identified against six different dimensions: political intention, legal, geographical, management, socio-economic and sustainability. The analysis shows potentials for synergies but also potential inconsistencies. We show that directives must be carefully coordinated to ensure coherent management and that synergies and site-specific goals, such as target areas, are important for sustainable management. Possible methodologies are described. IRBM can be considered as one possible approach towards sustainable development by coordinating different policies.

  • 187.
    Evers, Mariele
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Centre for Climate and Safety.
    Nyberg, Lars
    Karlstad University, Faculty of Social and Life Sciences, Centre for Climate and Safety.
    Coherence and inconsistency of European instruments for integrated river basin management2011Conference paper (Refereed)
    Abstract [en]

    Room for the River projects increase the level of flood protection by enlarging theconveyance and reducing hydraulic roughness. As a consequence sediment transportcapacities are reduced as well, causing shoals and a reduced navigation channel. Thelarge number of Room for the River measures and European Framework Directive(WFD) measures, aiming at an increase of the ecological potential (e.g. sidechannels), will result in much dredging, if no structural measures are implemented.The expected amount of dredging will be too large to handle. Therefore research isexecuted to limit the dredging effort by executing mitigating measures. Old principlesof irrigation are given new attention to be applied to side channels and channelsbetween longitudinal dams and the river bank ('bank channels'). A new round ofnormalisation works may be necessary, to limit dredging activities. Boundaryconditions for river managemant are stopping autonomous bed degradation andeconomic sustainability of sets of measures that can cope with the hydromorphologicconsequences of the Room for the River and WFD measures

  • 188.
    Evers, Mariele
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Centre for Climate and Safety. Bonn University.
    Nyberg, Lars
    Karlstad University, Faculty of Social and Life Sciences, Centre for Climate and Safety.
    Svedung, Inge
    Karlstad University, Faculty of Social and Life Sciences, Centre for Climate and Safety.
    Reducing flood risk by integrative land use planning2012In: Proceedings of the 43rd ESReDA seminar on land use planning and risk-informed decision making. Saint-Étienne-du Rouvray, France, Oct 22-23, 2012, 2012Conference paper (Refereed)
  • 189.
    Fagerlind, David
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Deconstructing the Great Acceleration2018Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    The Anthropocene is characterized by a strong human influence on the Earth System that is threatening the future prosperity of human societies. A mid-20th century onset of the Anthropocene is being proposed supported by the global phenomenon the Great Acceleration, but much concern has been raised that defining the Anthropocene based on global averages fails to recognize the massive inequalities in humanity’s contribution to current pressures on the Earth System. This study uses increase in growth rate as in indication of system change and conducts a statistical analysis to determine the largest change in the socio-economic domain of the Earth System on both a global and national level. The aim is to examine the empirical support for an unequal Anthropocene from a systems perspective. 814 of these events are identified across all the Great Acceleration indicators. The magnitude of the changes is typically large, with the growth rate increasing by more than 100% in 86% of the identified events. The findings suggest that while there is good evidence for a substantial change in the socio-economic domain of the Earth System the mid-20th century it is not the result of a globally synchronous event, but rather the culmination of a gradual process that display large temporal disparities with these system changes moving like waves across the Earth. The observed disparities show striking similarities to current developmental status suggesting that when deconstructed, the Great Acceleration can be used both to support global patterns and to illustrate inequalities between countries and people, making it a powerful tool to communicate the many facets of the Anthropocene.

  • 190.
    Fanting, Gong
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Linking socio-economic factors to urban growth by using night timelight imagery from 1992 to 2012: A case study in Beijing2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In recent decades, the night lights data of the Earth’s surface derived from the Defense Meteorological Satellite Program’s Operational Linescan System (DMSP/OLS) have been used to detect the human settlements and human activities, because the DMSP/OLS data is able to supply the information about the urban areas  and non-urban areas on the Earth which means it is more suitable for urban studies than usual satellite imagery data.

     

    The urban development is closed linked to the human society development. Therefore, studies of urban development will help people to understand how the urban changed and predict the urban change. The aim of this study was to detect Beijing’s urban development from 1992 to 2012, and find the contributions to the urban sprawl from socio-economic factors. Based on this objective, the main dataset used in this thesis was night lights images derived from the DMSP/OLS which was detected from  1992 to 2012. Due to the lacking of on-board calibration on OLS, and the over-glow of the lights resources, the information about the night lights cannot be extracted directly. Before any process, the night lights images should be calibrated. There is a method to calibrate the night light images which is called intercalibration. It is a second order regression model based method to find the related digital number values. Therefore, intercalibration was employed, and the threshold values were determined to extract urban areas in this study. Threshold value is useful for diffusing the over-glow effect, and finding the urban areas from the DMSP/OLS data. The methods to determine the threshold value in this thesis are empirical threshold method, sudden jump detection method, statistic data comparison method and k-mean clustering method. In addition, 13 socio-economic factors which included gross domestic product, urban population, permanent population, total energy consumption and so on were used to build the regression model. The contributions from these factors to the sum of the Beijing’s lights were found based on modeling.

     

    The results of this thesis are positive. The intercalibration was successful and all the DMSP/OLS data used in this study were calibrated. And then, the appropriate threshold values to extract the urban areas were figured out. The achieved urban areas were compared to the satellite images and the result showed that the urban areas were useful. During the time certain factors used in this study, such as mobile phone users, possession of civil vehicles, GDP, three positively highest contributed to urban development were close to 23%, 8% and 9%, respectively.

  • 191.
    Farineau, Anne
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Diamonds in the Rough: Remote predictive mapping using multispectral satellite imagery for kimberlite exploration on northeast Banks Island, NT2015Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    This study demonstrates the use and limitations of Remote Predictive Mapping (RPM) as an aid to kimberlite exploration on northeast Banks Island, Northwest Territories, Canada. It focuses on the effectiveness of ASTER and Landsat 8 optical multi-spectral satellite imagery for discerning the spectral properties of different bedrock and surficial materials that outcrop or blanket the regional terrain. Statistical algorithms and digital image enhancement techniques were used to highlight patterns and anomalies within each scene in order to determine the range of materials and specific deposits (e.g., till, glaciofluvial) that could be the source of recovered kimberlite indicator minerals (KIMs) from stream sediment samples. Field inspection and sampling were in part guided by these patterns and anomalies. During the course of fieldwork, numerous outliers of the Pliocene Beaufort Formation fluvial sand and gravel deposits were discovered on upland surfaces in northeastern Banks Island. These outcrops sit well beyond (east) of any previous mapped Beaufort Fm. extents, and it is hypothesized that as they exist within catchments where Industry has recovered KIMs, they could be a source of bedrock-inherited KIMs. Field observations and spectral sampling using a portable spectroradiometer were integrated with ASTER and Landsat data to predict the spatial extents of Beaufort Fm. deposits. Using test and field-validated Beaufort Fm. sites, Spectral Angle Mapper (SAM) whole pixel spectral target detection was compared with Matched Filtering (MF), Mixture-Tuned Matched Filtering (MTMF) sub-pixel spectral target detection methods and Parallelepiped classification for ASTER scenes 1228 and 0686.  Each method was also performed on ASTER scene 0541 to assess the potential for Quaternary sediment discrimination, using pixel ROIs from a field-validated glaciolacustrine deposit. The sub-pixel sensitivity of the MF/MTMF methods was determined to have the best potential for the discrimination of surficial materials on NE Banks Island.  MF/MTMF also had the best results for discriminating Beaufort Fm. in scene 1228, but Parallelepiped classification was the most effective prediction method for scene 0686. These inconsistent results indicate spectral variability between Beaufort Fm. sites, a consideration for any further study in the region.  

  • 192. Faucherre, Samuel
    et al.
    Jørgensen, Christian Juncher
    Blok, Daan
    Weiss, Niels
    Siewert, Matthias Benjamin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Physical Geography, Stockholm University,Stockholm, Sweden.
    Bang-Andreasen, Toke
    Hugelius, Gustaf
    Kuhry, Peter
    Elberling, Bo
    Short and Long-Term Controls on Active Layer and Permafrost Carbon Turnover Across the Arctic2018In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 123, no 2, p. 372-390Article in journal (Refereed)
    Abstract [en]

    Decomposition of soil organic matter (SOM) in permafrost terrain and the production of greenhouse gases is a key factor for understanding climate change-carbon feedbacks. Previous studies have shown that SOM decomposition is mostly controlled by soil temperature, soil moisture, and carbon-nitrogen ratio (C:N). However, focus has generally been on site-specific processes and little is known about variations in the controls on SOM decomposition across Arctic sites. For assessing SOM decomposition, we retrieved 241 samples from 101 soil profiles across three contrasting Arctic regions and incubated them in the laboratory under aerobic conditions. We assessed soil carbon losses (C-loss) five times during a 1year incubation. The incubated material consisted of near-surface active layer (AL(NS)), subsurface active layer (AL(SS)), peat, and permafrost samples. Samples were analyzed for carbon, nitrogen, water content, C-13, N-15, and dry bulk density (DBD). While no significant differences were observed between total AL(SS) and permafrost C-loss over 1year incubation (2.32.4% and 2.51.5% C-loss, respectively), AL(NS) samples showed higher C-loss (7.94.2%). DBD was the best explanatory parameter for active layer C-loss across sites. Additionally, results of permafrost samples show that C:N ratio can be used to characterize initial C-loss between sites. This data set on the influence of abiotic parameter on microbial SOM decomposition can improve model simulations of Arctic soil CO2 production by providing representative mean values of CO2 production rates and identifying standard parameters or proxies for upscaling potential CO2 production from site to regional scales.

  • 193. Fenn, Kaja
    et al.
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Bird, Anna
    Limonta, Mara
    Rittner, Martin
    Vermeesch, Pieter
    Ando, Sergio
    Garzanti, Eduardo
    Lu, Huayu
    Zhang, Hanzhi
    Lin, Zeng
    Insights into the provenance of the Chinese Loess Plateau from joint zircon U-Pb and garnet geochemical analysis of last glacial loess2018In: Quaternary Research, ISSN 0033-5894, E-ISSN 1096-0287, Vol. 89, no 3, p. 645-659Article in journal (Refereed)
    Abstract [en]

    The Chinese Loess Plateau, the world's largest and oldest loess record, preserves evidence of Asia's long-term dust source dynamics, but there is uncertainty over the source of the deposits. Recent single-grain detrital zircon U-Pb age analysis has progressed this issue, but debates remain about source changes, and the generation and interpretation of zircon data. To address this, we analyze different groupings of new and existing datasets from the Loess Plateau and potential sources. We also present the results of a first high resolution sampling, multi-proxy provenance analysis of Beiguoyuan loess using U-Pb dating of detrital zircons and detrital garnet geochemistry. The data shows that some small source differences seem to exist between different areas on the Loess Plateau. However, sediment source appears to be unchanging between loess and palaeosols, supporting a recent material recycling hypothesis. Our zircon and garnet data demonstrates, however, that Beiguoyuan experienced a temporary, abrupt source shift during the last glacial maximum, implying that local dust sources became periodically active during the Quaternary. Our results highlight that grouping data to achieve bigger datasets could cause identification of misleading trends. Additionally, we suggest that multi-proxy single-grain approaches are required to gain further insight into Chinese Loess Plateau dust sources.

  • 194.
    Figueiredo, Bruno
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Tsang, Chin-Fu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Lawrence Berkeley National Laboratory, Berkeley USA.
    Niemi, Auli
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Georg, Lindgren
    Swedish Radiation Safety Authority, Stockholm, Sweden.
    Review: The state-of-art of sparse channel models and their applicability to performance assessment of radioactive waste repositories in fractured crystalline formations2016In: Hydrogeology Journal, ISSN 1431-2174, E-ISSN 1435-0157, Vol. 24, no 7, p. 1607-1622Article in journal (Other academic)
    Abstract [en]

    Laboratory and field experiments done on fractured rock show that flow and solute transport often occur along flow channels. ‘Sparse channels’ refers to the case where these channels are characterised by flow in long flow paths separated from each other by large spacings relative to the size of flow domain. A literature study is presented that brings together information useful to assess whether a sparse-channel network concept is an appropriate representation of the flow system in tight fractured rock of low transmissivity, such as that around a nuclear waste repository in deep crystalline rocks. A number of observations are made in this review. First, conventional fracture network models may lead to inaccurate results for flow and solute transport in tight fractured rocks. Secondly, a flow dimension of 1, as determined by the analysis of pressure data in well testing, may be indicative of channelised flow, but such interpretation is not unique or definitive. Thirdly, in sparse channels, the percolation may be more influenced by the fracture shape than the fracture size and orientation but further studies are needed. Fourthly, the migration of radionuclides from a waste canister in a repository to the biosphere may be strongly influenced by the type of model used (e.g. discrete fracture network, channel model). Fifthly, the determination of appropriateness of representing an in situ flow system by a sparse-channel network model needs parameters usually neglected in site characterisation, such as the density of channels or fracture intersections.

  • 195.
    Figueiredo, Bruno
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Tsang, Chin-Fu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Lawrence Berkeley National Laboratory, Berkeley, California.
    Rutqvist, Jonny
    Lawrence Berkeley National Laboratory.
    Niemi, Auli
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Study of hydraulic fracturing processes in shale formations with complex geological settings2017In: Journal of Petroleum Science and Engineering, ISSN 0920-4105, E-ISSN 1873-4715, Vol. 152, p. 361-374Article in journal (Refereed)
    Abstract [en]

    Hydraulic fracturing has been applied to extract gas from shale-gas reservoirs. Complicated geological settings,such as spatial variability of the rock mass properties, local heterogeneities, complex in situ stress field, and preexistingbedding planes and faults, could make hydraulic fracturing a challenging task. In order to effectivelyand economically recover gas from such reservoirs, it is crucial to explore how hydraulic fracturing performs insuch complex geological settings. For this purpose, numerical modelling plays an important role because suchconditions cannot be reproduced by laboratory experiments. This paper focuses on the analysis of the influenceof confining formations and pre-existing bedding planes and faults on the hydraulically-induced propagation ofa vertical fracture, which will be called injection fracture, in a shale-gas reservoir. An elastic-brittle model basedon material property degradation was implemented in a 2D finite-difference scheme and used for rock elementssubjected to tension and shear failure. A base case is considered, in which the ratio SR between the magnitudesof the horizontal and vertical stresses, the permeability kc of the confining formations, the elastic modulus Epand initial permeability kp of the bedding plane and the initial fault permeability kF are fixed at reasonablevalues. In addition, the influence of multiple bedding planes, is investigated. Changes in pore pressure andpermeability due to high pressure injection lasting 2 h were analysed. Results show that in our case during theinjection period the fracture reaches the confining formations and if the permeability of those layers issignificantly larger than that of the shale, the pore pressure at the extended fracture tip decreases and fracturepropagation becomes slower. After shut-in, the pore pressure decreases more and the fracture does notpropagate any more. For bedding planes oriented perpendicular to the maximum principal stress direction andwith the same elastic properties as the shale formation, results were found not to be influenced by theirpresence. In such a scenario, the impact of multiple bedding planes on fracture propagation is negligible. On theother hand, a bedding plane softer than the surrounding shale formation leads to a fracture propagationasymmetrical vertically with respect to the centre of the injection fracture with a more limited upward fracturepropagation. A pre-existing fault leads to a decrease in fracture propagation because of fault reactivation withshear failure. This results in a smaller increase in injection fracture permeability and a slight higher injectionpressure than that observed without the fault. Overall, results of a sensitivity analysis show that fracturepropagation is influenced by the stress ratio SR, the permeability kc of the confining formations and the initialpermeability kp of the bedding plane more than the other major parameters.

    The full text will be freely available from 2019-03-07 08:00
  • 196.
    Fiola, Markus L.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Influence of Sample Preparation on Portable XRF-analyses of Aeolian Sediments: a Case Study2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The geochemical composition of aeolian sediments like windblown dust particles is of major importance for the exploration of dust origin and weathering conditions. This allows for the reconstruction of dust transport pathways and thus wind directions and palaeoclimate conditions. The loess deposits of the Carpathian Basin are the most complete terrestrial sediment climate archive in Europe, yet their development is still not fully understood. With the advancement of accurate field portable X-ray fluorescence (XRF) spectrometers, field applications have become possible, allowing in-situ geochemical analysis and potential advances in understanding the source of Carpathian Basin loess. However, previous work has failed to address the question of sample preparation and device interchangeability in the context of loess analyses.

    This study uses both Bruker Tracer 5i and Titan S1, as well as secondary data obtained with an Ametek SpectroXepos, to investigate sample preparation influences on aeolian sediment samples from Irig (Serbia) and Madaras (Hungary). Results showed that although absolute values deviate substantially between devices using different calibrations, some elemental ratios like Ca/Ti or Rb/Sr can still be compared when only relative changes are interpreted. Absolute concentrations of light elements, such as magnesium and calcium, were strongly influenced by milling or acid treatment. Absolute concentrations of light elements were also strongly influenced by changes in sample moisture, whereas the effect on the absolute concentrations of heavier elements was comparably small. Results also show that the influence of sample moisture needs to be considered when computing paleoclimatic indicator ratios involving aluminium or strontium, as sample moisture has a strong effect on the absolute concentration of these elements.

    Most deviations in measured absolute concentrations between untreated and prepared samples were attributed to the special nature of compositional data and could be removed through the application of additive or centred log-ratio transformations. This highlights the importance of considering the closure effect, using proper and robust statistical analyses in sediment provenance research.The geochemical data provided in this study shed light on dust provenance and the paleoclimatic development of the southeast European loess and highlight the effects of analysis technique on interpretation of this geochemical data.

    The full text will be freely available from 2019-08-01 08:01
  • 197. Fontorbe, G.
    et al.
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    De La Rocha, C. L.
    Hendry, K. R.
    Conley, D. J.
    A silicon depleted North Atlantic since the Palaeogene: Evidence from sponge and radiolarian silicon isotopes2016In: Earth and Planetary Science Letters, Vol. 453, p. 67-77Article in journal (Refereed)
    Abstract [en]

    Despite being one of Earth's major geochemical cycles, the evolution of the silicon cycle has received little attention and changes in oceanic dissolved silica (DSi) concentration through geologic time remain poorly constrained. Silicon isotope ratios (expressed as delta Si-30) in marine microfossils are becoming increasingly recognised for their ability to provide insight into silicon cycling. In particular, the delta Si-30 of siliceous sponge spicules has been demonstrated to be a useful proxy for past DSi concentrations. We analysed delta Si-30 in radiolarian tests and sponge spicules from the Blake Nose Palaeoceanographic Transect (ODP Leg 171B) spanning the Palaeocene-Eocene (ca. 60-30 Ma). Our delta Si-30 results range from +0.32 to +1.67 parts per thousand and -0.48 to +0.63 parts per thousand for the radiolarian and sponge records, respectively. Using an established relationship between ambient dissolved Si (DSi) concentrations and the magnitude of silicon isotope fractionation in siliceous sponges, we demonstrate that the Western North Atlantic was DSi deplete during the Palaeocene-Eocene throughout the water column, a conclusion that is robust to a range of assumptions and uncertainties. These data can constitute constraints on reconstructions of past-ocean circulation. Previous work has suggested ocean DSi concentrations were higher than modern ocean concentrations prior to the Cenozoic and has posited a drawdown during the Early Palaeogene due to the evolutionary expansion of diatoms. Our results challenge such an interpretation. We suggest here that if such a global decrease in oceanic DSi concentrations occurred, it must predate 60 Ma. (C) 2016 The Authors. Published by Elsevier B.V.

  • 198. Fontorbe, Guillaume
    et al.
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    De La Rocha, Christina
    Hendry, Kate
    Carstensen, Jacob
    Conley, Daniel
    Enrichment of dissolved silica in the deep equatorial Pacific during the Eocene-Oligocene2017In: Paleoceanography, ISSN 0883-8305, E-ISSN 1944-9186, Vol. 32, p. 848-863Article in journal (Refereed)
    Abstract [en]

    Silicon isotope ratios (expressed as δ30Si) in marine microfossils can provide insights into silica cycling over geologic time. Here we used δ30Si of sponge spicules and radiolarian tests from the Paleogene Equatorial Transect (Ocean Drilling Program Leg 199) spanning the Eocene and Oligocene (~50–23 Ma) to reconstruct dissolved silica (DSi) concentrations in deep waters and to examine upper ocean δ30Si. The δ30Si values range from 3.16 to +0.18‰ and from 0.07 to +1.42‰ for the sponge and radiolarian records, respectively. Both records show a transition toward lower δ30Si values around 37 Ma. The shift in radiolarian δ30Si is interpreted as a consequence of changes in the δ30Si of source DSi to the region. The decrease in sponge δ30Si is interpreted as a transition from low DSi concentrations to higher DSi concentrations, most likely related to the shift toward a solely Southern Ocean source of deep water in the Pacific during the Paleogene that has been suggested by results from paleoceanographic tracers such as neodymium and carbon isotopes. Sponge δ30Si provides relatively direct information about the nutrient content of deep water and is a useful complement to other tracers of deep water circulation in the oceans of the past. 

  • 199.
    Fors, Yvonne
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Jalilehvand, Farideh
    Risberg, Emiliana Damian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bjordal, Charlotte
    Phillips, Ebba
    Sandström, Magnus
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sulfur and iron analyses of marine archaeological wood in shipwrecks from the Baltic Sea and Scandinavian waters2012In: Journal of Archaeological Science, ISSN 0305-4403, E-ISSN 1095-9238, Vol. 39, no 7, p. 2521-2532Article in journal (Refereed)
    Abstract [en]

    Analyses of marine archaeological wood from shipwrecks in the Baltic Sea area, Kronan, Riksnyckeln, Tattran, the Puck Bay Boat and the Ghost wreck, and at the Scandinavian West coast, the Gota wreck, Stora Sofia and the Viking shipwrecks of Skuldelev, show accumulation of sulfur compounds. The penetration profiles of sulfur and iron into the wood and the speciation of characteristic sulfur groups were evaluated by combining X-ray spectroscopic analyses, in particular S K-edge XANES (X-ray absorption near edge structure) and X-ray fluorescence, with ESCA and elemental analyses. The combined analyses support the hypothesis that hydrogen sulfide produced by sulfate-reducing bacteria reacts and accumulates at low iron concentration mainly as organically bound sulfur, which as in previous studies was found by X-ray spectro-microscopy to accumulate in lignin-rich parts of the wood cell walls. The presence of iron(II) ions from corroding iron promotes formation of pyrite and other iron(II) sulfides, which easily oxidise in aerobic conditions with high humidity. No significant differences in sulfur and iron accumulation were found in wood from shipwrecks in the east coast brackish water and the west coast seawater. Sediments from three wreck sites, the Gota wreck, Stora Sofia and Kronan, were analyzed to a depth of a few decimeters and showed especially at the Stora Sofia high sulfur concentrations, exceeding 3 mass%. S K-edge XANES analyses of the sediments showed mainly reduced forms of sulfur, in particular pyrite and iron(II) sulfides together with elemental sulfur.

  • 200.
    Forsström, Anna
    Swedish Museum of Natural History, Department of Geology. Linköping University.
    Extraction and determination of Hf in water using a chelating resin and ICP-AES2014Student paper other, 10 HE creditsStudent thesis
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