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Author Dutova, E.M.; Nikitenkov, A.N.; Pokrovskiy, V.D.; Banks, D.; Frengstad, B.S.; Parnachev, V.P. url  openurl
  Title Modelling of the dissolution and reprecipitation of uranium under oxidising conditions in the zone of shallow groundwater circulation Type Journal Article
  Year (down) 2017 Publication Journal of Environmental Radioactivity Abbreviated Journal  
  Volume 178-179 Issue Pages 63-76  
  Keywords Groundwater, Hydrochemical modelling, Mineralisation, Natural uranium, Ore, Solubility  
  Abstract Generic hydrochemical modelling of a grantoid-groundwater system, using the Russian software “HydroGeo”, has been carried out with an emphasis on simulating the accumulation of uranium in the aqueous phase. The baseline model run simulates shallow granitoid aquifers (U content 5 ppm) under conditions broadly representative of southern Norway and southwestern Siberia: i.e. temperature 10 °C, equilibrated with a soil gas partial CO2 pressure (PCO2, open system) of 10−2.5 atm. and a mildly oxidising redox environment (Eh = +50 mV). Modelling indicates that aqueous uranium accumulates in parallel with total dissolved solids (or groundwater mineralisation M – regarded as an indicator of degree of hydrochemical evolution), accumulating most rapidly when M = 550–1000 mg L−1. Accumulation slows at the onset of saturation and precipitation of secondary uranium minerals at M = c. 1000 mg L−1 (which, under baseline modelling conditions, also corresponds approximately to calcite saturation and transition to Na-HCO3 hydrofacies). The secondary minerals are typically “black” uranium oxides of mixed oxidation state (e.g. U3O7 and U4O9). For rock U content of 5–50 ppm, it is possible to generate a wide variety of aqueous uranium concentrations, up to a maximum of just over 1 mg L−1, but with typical concentrations of up to 10 μg L−1 for modest degrees of hydrochemical maturity (as indicated by M). These observations correspond extremely well with real groundwater analyses from the Altai-Sayan region of Russia and Norwegian crystalline bedrock aquifers. The timing (with respect to M) and degree of aqueous uranium accumulation are also sensitive to Eh (greater mobilisation at higher Eh), uranium content of rocks (aqueous concentration increases as rock content increases) and PCO2 (low PCO2 favours higher pH, rapid accumulation of aqueous U and earlier saturation with respect to uranium minerals).  
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  ISSN 0265-931x ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ dutova_modelling_2017 Serial 114  
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Author Post, V.E.A.; Vassolo, S.I.; Tiberghien, C.; Baranyikwa, D.; Miburo, D. url  openurl
  Title Weathering and evaporation controls on dissolved uranium concentrations in groundwater – A case study from northern Burundi Type Journal Article
  Year (down) 2017 Publication Science of The Total Environment Abbreviated Journal  
  Volume 607-608 Issue Pages 281-293  
  Keywords Geochemical modelling, Hydrochemistry, Lake Tshohoha South, Public health, Radionuclides, Water supply  
  Abstract The potential use of groundwater for potable water supply can be severely compromised by natural contaminants such as uranium. The environmental mobility of uranium depends on a suite of factors including aquifer lithology, redox conditions, complexing agents, and hydrological processes. Uranium concentrations of up to 734μg/L are found in groundwater in northern Burundi, and the objective of the present study was to identify the causes for these elevated concentrations. Based on a comprehensive data set of groundwater chemistry, geology, and hydrological measurements, it was found that the highest dissolved uranium concentrations in groundwater occur near the shores of Lake Tshohoha South and other smaller lakes nearby. A model is proposed in which weathering and evapotranspiration during groundwater recharge, flow and discharge exert the dominant controls on the groundwater chemical composition. Results of PHREEQC simulations quantitatively confirm this conceptual model and show that uranium mobilization followed by evapo-concentration is the most likely explanation for the high dissolved uranium concentrations observed. The uranium source is the granitic sand, which was found to have a mean elemental uranium content of 14ppm, but the exact mobilization process could not be established. Uranium concentrations may further be controlled by adsorption, especially where calcium-uranyl‑carbonate complexes are present. Water and uranium mass balance calculations for Lake Tshohoha South are consistent with the inferred fluxes and show that high‑uranium groundwater represents only a minor fraction of the overall water input to the lake. These findings highlight that the evaporation effects that cause radionuclide concentrations to rise to harmful levels in groundwater discharge areas are not only confined to arid regions, and that this should be considered when selecting suitable locations for water supply wells.  
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  ISSN 0048-9697 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ post_weathering_2017 Serial 132  
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Author Etschmann, B.; Liu, W.; Li, K.; Dai, S.; Reith, F.; Falconer, D.; Kerr, G.; Paterson, D.; Howard, D.; Kappen, P.; Wykes, J.; Brugger, J. url  openurl
  Title Enrichment of germanium and associated arsenic and tungsten in coal and roll-front uranium deposits Type Journal Article
  Year (down) 2017 Publication Chemical Geology Abbreviated Journal  
  Volume 463 Issue Pages 29-49  
  Keywords Arsenic, Coal, EXAFS and XANES, germanium, Hydrothermal fluids, Metallogenesis, Speciation, Tungsten  
  Abstract Most of the World’s germanium (Ge) is mined from Ge-rich lignite, where it is commonly associated with elevated arsenic (As), tungsten (W) and beryllium (Be) contents. Over the past decade, new evidence showing that World-class Ge deposits result from the interaction of hydrothermal fluids with organic matter in coal seams has emerged. Yet, the chemical state of Ge and associated metals in lignite remains poorly understood. We used Mega-pixel Synchrotron X-ray Fluorescence (MSXRF), X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) to characterize the oxidation states and chemical bonding environment of Ge, As, and W in two world-class Mesozoic Ge-in-lignite deposits (Lincang, Yunnan, southwestern China; Wulantuga, Inner Mongolia, northeastern China); in lignite-bearing uranium (U) ores from the Beverley deposit (South Australia) hosted in Eocene sandstones; and in lignite and preserved wood in late Oligocene-Miocene fluviatile sediments (Gore, Southland, New Zealand). The aim was to improve our understanding of the enrichment mechanism of Ge in lignite and better evaluate the environmental mobility of Ge and some of the associated metals (specifically As and W) in lignite ores. In all samples, chemical maps show that Ge is distributed homogeneously (down to 2μm) within the organic matter. XANES and EXAFS data show that Ge exists in the tetravalent oxidation state and in a distorted octahedral coordination with O, consistent with complexing of Ge by organic ligands. In some pyrite-bearing samples, a minor fraction of Ge is also present as Ge(IV) in association with pyrite. In contrast, As displays a more complex speciation pattern, sometimes even in a single sample, including As(III), As(V), and As(−I/+II) in solid solution in sulfides. Arsenic in sulfides occurs in anionic and cationic forms, i.e., it shows both the common substitution for S22− and the substitution for Fe recently discovered in some hydrothermal pyrites. Tungsten was present as W(VI) in distorted octahedral (3+3) coordination. The EXAFS data confirm the absence or minor contribution of individual W-rich minerals such as scheelite or ferberite to W mass balance in the studied samples. These data show that Ge, W, and probably some As are scavenged via formation of insoluble, oxygen-bridged metal organic complexes in lignite. Destruction of the organic ligands responsible for fixing Ge and W (As) in these lignites is required for liberating the metals, e.g. from waste materials. Geochemical modelling suggests that Ge, W, Be and As all can be extracted from granitic rocks by dilute, low temperature hydrothermal fluids. Germanium is transported mainly as the tetrahedral Ge(OH)4(aq) complex, but fixed as an octahedral oxy-bridged organic complex. The same situation is valid for W, which is transported at the tetrahedral tungstate ion, but most likely scavenged via formation of a 6-coordinated metal-organic species. The Ge-Be-W±As association in Ge-rich coals reflects the source of the metals as well as related scavenging mechanisms.  
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  ISSN 0009-2541 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ etschmann_enrichment_2017 Serial 183  
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Author Bullock, L.A.; Parnell, J. url  openurl
  Title Selenium and molybdenum enrichment in uranium roll-front deposits of Wyoming and Colorado, USA Type Journal Article
  Year (down) 2017 Publication Journal of Geochemical Exploration Abbreviated Journal  
  Volume 180 Issue Pages 101-112  
  Keywords Molybdenum, Roll-fronts, Selenium, Tellurium, Uranium, Wyoming  
  Abstract Sandstone uranium (U) roll-front deposits of Wyoming and Colorado (USA) are important U resources, and may provide a terrestrial source for critical accessory elements, such as selenium (Se), molybdenum (Mo), and tellurium (Te). Due to their associated toxicity, MoSeTe occurrences in roll-fronts should also be carefully monitored during U leaching and ore processing. While elevated MoSe concentrations in roll-fronts are well established, very little is known about Te occurrence in such deposits. This study aims to establish MoSeTe concentrations in Wyoming and Colorado roll-fronts, and assess the significance of these deposits in an environmental and mineral exploration context. Sampled roll-front deposits, produced by oxidized groundwater transportation through a sandstone, show high MoSe content in specific redox zones, and low Te, relative to crustal means. High Se concentrations (up to 168ppm) are restricted to a narrow band of alteration at the redox front. High Mo content (up to 115ppm) is typically associated with the reduced mineralized nose and seepage zones of the roll-front, ahead of the U orebody. Elevated trace element concentrations are likely sourced from proximal granitic intrusions, tuffaceous deposits, and local pyritic mudstones. Elevated MoSe content in the sampled roll fronts may be regarded as a contaminant in U in-situ recovery and leaching processing, and may pose an environmental threat in groundwaters and soils, so extraction should be carefully monitored. The identification of peak concentrations of MoSe can also act as a pathfinder for the redox front of a roll-front, and help to isolate the U orebody, particularly in the absence of gamma signatures.  
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  ISSN 0375-6742 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ bullock_selenium_2017 Serial 189  
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Author Abiye, T. url  openurl
  Title Synthesis on groundwater recharge in Southern Africa: A supporting tool for groundwater users Type Journal Article
  Year (down) 2016 Publication Groundwater for Sustainable Development Abbreviated Journal  
  Volume 2-3 Issue Pages 182-189  
  Keywords Arid and semi-arid areas, Groundwater recharge, Recharge estimation methods, Southern Africa  
  Abstract This synthesis on groundwater recharge targets the Southern African region as a result of the dependence of the community and economic sector on the groundwater resource. Several literature based recharge studies were collected and assessed in order to find out the main controls to the occurrence of recharge. The Water Table Fluctuation and Base flow separation methods have been tested in the catchment that drains crystalline basement rocks and dolostones close to the city of Johannesburg, South Africa. Based on the assessed data the Chloride Mass Balance method resulted in groundwater recharge of less than 4% of the rainfall, while it reaches 20%, when rainfall exceeds 600mm. For the classical water balance method, recharge proportion is less than 3% of rainfall as a result of very high ambient temperature in the region. Based on the Saturated Volume Fluctuation and Water Table Fluctuation methods, recharge could be less than 6% for annual rainfall of less than 600mm. Observational results further suggest that sporadic recharge from high intensity rainfall has important contribution to the groundwater recharge in the region, owing to the presence of permeable geological cover, which could not be fully captured by most of the recharge estimation methods. This study further documents an evaluation of the most reliable recharge estimation methods in the area such as the chloride mass balance, saturated volume fluctuation and water table fluctuation methods in order to successfully manage the groundwater resource.  
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  ISSN 2352-801x ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ abiye_synthesis_2016 Serial 101  
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Author Lim, S.; Chase, B.M.; Chevalier, M.; Reimer, P.J. url  openurl
  Title 50,000years of vegetation and climate change in the southern Namib Desert, Pella, South Africa Type Journal Article
  Year (down) 2016 Publication Palaeogeography, Palaeoclimatology, Palaeoecology Abbreviated Journal  
  Volume 451 Issue Pages 197-209  
  Keywords Climate reconstruction, Late Quaternary, Namib Desert, Pollen, Rock hyrax middens, South Africa  
  Abstract This paper presents the first continuous pollen record from the southern Namib Desert spanning the last 50,000years. Obtained from rock hyrax middens found near the town of Pella, South Africa, these data are used to reconstruct vegetation change and quantitative estimates of temperature and aridity. Results indicate that the last glacial period was characterised by increased water availability at the site relative to the Holocene. Changes in temperature and potential evapotranspiration appear to have played a significant role in determining the hydrologic balance. The record can be considered in two sections: 1) the last glacial period, when low temperatures favoured the development of more mesic Nama-Karoo vegetation at the site, with periods of increased humidity concurrent with increased coastal upwelling, both responding to lower global/regional temperatures; and 2) the Holocene, during which time high temperatures and potential evapotranspiration resulted in increased aridity and an expansion of the Desert Biome. During this latter period, increases in upwelling intensity created drier conditions at the site. Considered in the context of discussions of forcing mechanisms of regional climate change and environmental dynamics, the results from Pella stand in clear contrast with many inferences of terrestrial environmental change derived from regional marine records. Observations of a strong precessional signal and interpretations of increased humidity during phases of high local summer insolation in the marine records are not consistent with the data from Pella. Similarly, while high percentages of Restionaceae pollen has been observed in marine sediments during the last glacial period, they do not exceed 1% of the assemblage from Pella, indicating that no significant expansion of the Fynbos Biome has occurred during the last 50,000years. These findings pose interesting questions regarding the nature of environmental change in southwestern Africa, and the significance of the diverse records that have been obtained from the region.  
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  ISSN 0031-0182 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ lim_50000years_2016 Serial 107  
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Author Saini, K.; Singh, P.; Bajwa, B.S. url  openurl
  Title Comparative statistical analysis of carcinogenic and non-carcinogenic effects of uranium in groundwater samples from different regions of Punjab, India Type Journal Article
  Year (down) 2016 Publication Applied Radiation and Isotopes Abbreviated Journal  
  Volume 118 Issue Pages 196-202  
  Keywords Carcinogenic, Groundwater, LED fluorimeter, Uranium  
  Abstract LED flourimeter has been used for microanalysis of uranium concentration in groundwater samples collected from six districts of South West (SW), West (W) and North East (NE) Punjab, India. Average value of uranium content in water samples of SW Punjab is observed to be higher than WHO, USEPA recommended safe limit of 30µgl−1 as well as AERB proposed limit of 60µgl−1. Whereas, for W and NE region of Punjab, average level of uranium concentration was within AERB recommended limit of 60µgl−1. Average value observed in SW Punjab is around 3–4 times the value observed in W Punjab, whereas its value is more than 17 times the average value observed in NE region of Punjab. Statistical analysis of carcinogenic as well as non carcinogenic risks due to uranium have been evaluated for each studied district.  
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  ISSN 0969-8043 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number THL @ christoph.kuells @ saini_comparative_2016 Serial 130  
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Author Jaireth, S.; Roach, I.C.; Bastrakov, E.; Liu, S. url  openurl
  Title Basin-related uranium mineral systems in Australia: A review of critical features Type Journal Article
  Year (down) 2016 Publication Ore Geology Reviews Abbreviated Journal  
  Volume 76 Issue Pages 360-394  
  Keywords Australia’s uranium deposits, Calcrete-uranium, Sandstone-hosted uranium, Unconformity-related uranium  
  Abstract This paper reviews critical features of basin-related uranium mineral systems in Australia. These mineral systems include Proterozoic unconformity-related uranium systems formed predominantly from diagenetic fluids expelled from sandstones overlying the unconformity, sandstone-hosted uranium systems formed from the influx of oxidised groundwaters through sandstone aquifers, and calcrete uranium systems formed from oxidised groundwaters flowing through palaeochannel aquifers (sand and calcrete). The review uses the so-called ‘source-pathway-trap’ paradigm to summarise critical features of fertile mineral systems. However, the scheme is expanded to include information on the geological setting, age and relative timing of mineralisation, and preservation of mineral systems. The critical features are also summarised in three separate tables. These features can provide the basis to conduct mineral potential and prospectivity analysis in an area. Such analysis requires identification of mappable signatures of above-mentioned critical features in geological, geophysical and geochemical datasets. The review of fertile basin-related systems shows that these systems require the presence of at least four ingredients: a source of leachable uranium (and vanadium and potassium for calcrete-uranium deposits); suitable hydrological architecture enabling connection between the source and the sink (site of accumulation); physical and chemical sinks or traps; and a post-mineralisation setting favourable for preservation. The review also discusses factors that may control the efficiency of mineral systems, assuming that world-class deposits result from more efficient mineral systems. The review presents a brief discussion of factors which may have controlled the formation of large deposits in the Lake Frome region in South Australia, the Chu-Sarysu and Syrdarya Basins in Kazakhstan and calcrete uranium deposits in the Yilgarn region, Western Australia.  
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  ISSN 0169-1368 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ jaireth_basin-related_2016 Serial 139  
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Author Carrión, A.; Fornes, A. url  openurl
  Title Underground medieval water distribution network in a Spanish town Type Journal Article
  Year (down) 2016 Publication Tunnelling and Underground Space Technology Abbreviated Journal  
  Volume 51 Issue Pages 90-97  
  Keywords Water distribution, Underground cistern, Medieval tunnel  
  Abstract The city of Alcudia de Crespins, in the centre of the Valencia province (east of Spain), has an exceptional water distribution system that in the past served fresh water to many houses in the town. This system is formed by more than one km of tunnels and underground cisterns, and dates probably in the late medieval times, while it has been in use and suffering modifications until 1955. This paper presents the structure and characteristics of such exceptional system, and explains the functioning parameters of the infrastructure.  
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  ISSN 0886-7798 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ Carrion201690 Serial 264  
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Author Külls, C.; Jobin, J.; Weiler, M. openurl 
  Title Environmental analytics for water carbon management: enable WCM: Schlussbericht Type Report
  Year (down) 2015 Publication Abbreviated Journal  
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  Address  
  Corporate Author Thesis  
  Publisher Albert Ludwigs Universität, Professur für Hydrologie Place of Publication Editor  
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  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number THL @ christoph.kuells @ Kuells2015environmental Serial 65  
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