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  • 1.
    Andrén, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Science.
    Development of the Laitaure Delta, Swedish Lappland: A Study of Growth, Distributary Forms and Processes1994Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Deltaic processes were studied on the Laitaure delta. Specific aims were to: analyse forms and processes in distributaries with regard to hydraulic geometry relationships; investigate the distribution of water into different distributaries; analyse the morphological development of the delta; and quantify the advance of the delta front. Further, a brief study was made of the bottom sediments in Lake Laitaure.

    It was concluded that distributaries may be distinguished by at-a-station hydraulic geometry relationships, depending on their state of activity and their location in the delta, i.e. distance to the delta front.

    Differences in activity between distributaries were also shown by the “delta” (analogous to downstream) hydraulic geometry relationships. Large similarities in “delta” hydraulic geometry were found between the Laitaure delta and the Volga and Danube deltas (cf. Mikhailov, 1970).

    It was found that the discharge in a distributary is linearly related to the total discharge in Rapaälven, and that the main distributary system may, inter alia, be distinguished from the other systems by its: (1) higher rate of increase in discharge with total discharge;  (2) decreasing proportion of the total discharge as this increases. Threshold discharges, i.e. the total water discharge in Rapaälven below which a channel has zero discharge, were determined for the “secondary” distributaries.

    The temporal variation in flow distribution is indicated by, for example, changes in the rate of deltaic advance at different mouths and aggradation of channel beds within distributary systems that have experienced reduced flows. It is concluded that the flow distribution is an important factor to be considered in studies of river deltas.

    The delta is growing by about 0.38 km2/year, equivalent to an advance of the delta front by approx. 4.5 m/year. Disintegration of vegetation is abundant all over the delta except for the distal parts. However, the proportion of delta lake area has decreased and the proportion of vegetated area has increased due to miniature delta formation, and deltaic growth.

    X-ray radiographs of sediment cores sampled in different parts of Laitaure, reveal annually laminated deposits, for which the variations in temporal and spatial sedimentation rates were investigated.

  • 2.
    Cajas, Margarita
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Science.
    Genesis and Diagenesis of the Phosphatic Hardground of the Holm Dal Formation (Late Middle Cambrian), North Greenland1997Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The phosphatic hardground of the Holm Dal Formation (late Middle Cambrian) of North Greenland is composed of two parts: one basal with abundant allochthonous material and an upper part without an allochthonous component. It was formed by release of phosphate, by bacterial degradation, from organic matter which accumulated in lime mudstones on which the hardground developed.

    Following its release to pore water, the phosphate precipitated as apatite forming the hardground, in which cyanobacterial assemblages fossilized. Echinoderm holdfasts are a conspicuous feature of the hardground.

    REE analysis and the well preserved cyanobacterial fossils point towards an early diagenesis. The same REE analysis and the existence of bitumen in the samples, indicate dysaerobic conditions during the formation of the hardground.

    Isotopes analysis (143Nd and 144Nd) underline the marine biogenic character of the apatite.

  • 3.
    Ljungberg, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Science.
    Evaluation of stimulated reductivedechlorination in situ of chlorinatedsolvents at a site in Huddinge: using principal component analysis, partialleast square regression and degradation2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The method of using stimulated reductive dechlorination when remediating sites contaminated with chlorinated solvents is not unusual, but not many studies have been done on the overall process outside of a controlled environment. In order to investigate the process, principal component analysis (PCA) and partial least square (PLS) regression was used to identify the most important parameters for the degradation of the chlorinated solvents. The most important parameter for all chlorinated compounds turned out to be oxygen, with levels of degradation products increasing with decreasing levels of dissolved oxygen. Dissolved oxygen was deemed the most important variable to measure during a control program on the site.

    The degradation dynamics of the process were investigated to examine the behaviour of the chlorinated solvents and their degradation products. The degradation products of the main contaminant TCE were found in all observation points, which indicates an ongoing reductive dechlorination all over the site. A large amount of the mother product, TCE, was found in two observation points, which were believed to be situated close to the sources of the TCE contamination. Over the observation period of 2,5 years the levels of TCE in the source areas decreased significantly to below the remediation goal. However, the levels of TCE increased in another observation point further downstream, with concentrations still increasing at the end of this study. The levels in this point were lower than those measured initially in the source area, but still much higher than the accepted values. Possible reasons for this appearance of TCE could be an isolated sheet of contaminants being pushed into the observation point from a nearby location or transport of the contaminants from the source area in units of higher conductivity such as sand lenses or fractures in the clayey soil.

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