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Author Schwiede, M.; Duijnisveld, W.H.M.; Böttcher, J. url  openurl
  Title Investigation of processes leading to nitrate enrichment in soils in the Kalahari Region, Botswana Type Journal Article
  Year 2005 Publication Physics and Chemistry of the Earth, Parts A/B/C Abbreviated Journal  
  Volume 30 Issue (down) 11 Pages 712-716  
  Keywords Nitrate, Arenosol soils, Semi-arid, Kalahari, Cattle, Chloride, Travel time  
  Abstract In Southern Africa elevated nitrate concentrations are observed in mostly uninhabited semi-arid areas. In the Kalahari of Botswana groundwater locally exhibits concentrations up to 600mg/l. It is assumed, that nitrate found in the groundwater originates mainly from nitrogen input and transformations in the soils. Our investigations in the Kalahari between Serowe and Orapa show that cattle raising is an important source for enhanced nitrate concentrations in the soils (Arenosols). But also in termite mounds very high nitrate stocks were found, and under natural vegetation (acacia trees and shrubs) nitrate concentrations were mostly unexpectedly high. This nitrate enrichment in the soils poses a serious threat to the groundwater quality. However, calculated soil water age distributions in the unsaturated zone clearly show that today’s nitrate pollution of the groundwater below the investigation area could originate from natural sources, but cannot be caused by the current land use for cattle raising.  
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  ISSN 1474-7065 ISBN Medium  
  Area Expedition Conference  
  Notes Integrated Water Resources Management (IWRM) and the Millennium Development Goals: Managing Water for Peace and Prosperity Approved no  
  Call Number THL @ christoph.kuells @ Schwiede2005712 Serial 276  
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Author Külls, C. openurl 
  Title Rekonstruktion hydrologischer Extreme in der Namibwüste Type Journal Article
  Year 2011 Publication Berichte der naturforschenden Gesellschaft zu Freiburg im Breisgau Abbreviated Journal  
  Volume Issue (down) 101 Pages 69-81  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ Serial 71  
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Author Zhao, Y.; Li, X.; Lei, L.; Chen, L.; Luo, Z. url  openurl
  Title Permeability evolution mechanism and the optimum permeability determination of uranium leaching from low-permeability sandstone treated with low-frequency vibration Type Journal Article
  Year 2023 Publication Journal of Rock Mechanics and Geotechnical Engineering Abbreviated Journal  
  Volume 15 Issue (down) 10 Pages 2597-2610  
  Keywords Chemical reactive rate, Low-frequency vibration, Low-permeability sandstone, Optimum permeability, Permeability evolution mechanism, Uranium migration  
  Abstract Low-frequency vibrations can effectively improve natural sandstone permeability, and higher vibration frequency is associated with larger permeability. However, the optimum permeability and permeability evolution mechanism for uranium leaching and the relationship between permeability and the change of chemical reactive rate affecting uranium leaching have not been determined. To solve the above problems, in this study, identical homogeneous sandstone samples were selected to simulate low-permeability sandstone; a permeability evolution model considering the combined action of vibration stress, pore water pressure, water flow impact force, and chemical erosion was established; and vibration leaching experiments were performed to test the model accuracy. Both the permeability and chemical reactions were found to simultaneously restrict U6+ leaching, and the vibration treatment increased the permeability, causing the U6+ leaching reaction to no longer be diffusion-constrained but to be primarily controlled by the reaction rate. Changes of the model calculation parameters were further analyzed to determine the permeability evolution mechanism under the influence of vibration and chemical erosion, to prove the correctness of the mechanism according to the experimental results, and to develop a new method for determining the optimum permeability in uranium leaching. The uranium leaching was found to primarily follow a process consisting of (1) a permeability control stage, (2) achieving the optimum permeability, (3) a chemical reactive rate control stage, and (4) a channel flow stage. The resolution of these problems is of great significance for facilitating the application and promotion of low-frequency vibration in the CO2 + O2 leaching process.  
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  ISSN 1674-7755 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ zhao_permeability_2023 Serial 198  
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Author Leibundgut, C.; Maloszewski, P.; Külls, C. url  doi
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  Title Tracers in Hydrology Type Book Whole
  Year 2009 Publication Abbreviated Journal  
  Volume Issue (down) 1. Ed. Pages  
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  Publisher John Wiley & Sons, Ltd Place of Publication Editor  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ Leibundgut2009tracers Serial 37  
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Author Morin, E.; Grodek, T.; Dahan, O.; Benito, G.; Külls, C.; Jacoby, Y.; Van Langenhove, G.; Seely, M.; Enzel, Y. url  doi
openurl 
  Title Flood routing and alluvial aquifer recharge along the ephemeral arid Kuiseb River, Namibia Type Journal Article
  Year 2009 Publication Journal of Hydrology Abbreviated Journal  
  Volume 368 Issue (down) 1-4 Pages 262-275  
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  Publisher Elsevier Place of Publication Editor  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ Morin2009flood Serial 26  
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