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Author |
Schwiede, M.; Duijnisveld, W.H.M.; Böttcher, J. |
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Title |
Investigation of processes leading to nitrate enrichment in soils in the Kalahari Region, Botswana |
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Journal Article |
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2005 |
Publication |
Physics and Chemistry of the Earth, Parts A/B/C |
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30 |
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11 |
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712-716 |
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Keywords |
Nitrate, Arenosol soils, Semi-arid, Kalahari, Cattle, Chloride, Travel time |
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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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1474-7065 |
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Integrated Water Resources Management (IWRM) and the Millennium Development Goals: Managing Water for Peace and Prosperity |
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no |
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Call Number |
THL @ christoph.kuells @ Schwiede2005712 |
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276 |
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Author |
Külls, C. |
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Title |
Rekonstruktion hydrologischer Extreme in der Namibwüste |
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Journal Article |
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Year |
2011 |
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Berichte der naturforschenden Gesellschaft zu Freiburg im Breisgau |
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101 |
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69-81 |
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THL @ christoph.kuells @ |
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71 |
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Author |
Zhao, Y.; Li, X.; Lei, L.; Chen, L.; Luo, Z. |
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Title |
Permeability evolution mechanism and the optimum permeability determination of uranium leaching from low-permeability sandstone treated with low-frequency vibration |
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Journal Article |
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Year |
2023 |
Publication |
Journal of Rock Mechanics and Geotechnical Engineering |
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15 |
Issue |
10 |
Pages |
2597-2610 |
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Keywords |
Chemical reactive rate, Low-frequency vibration, Low-permeability sandstone, Optimum permeability, Permeability evolution mechanism, Uranium migration |
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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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1674-7755 |
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THL @ christoph.kuells @ zhao_permeability_2023 |
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198 |
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Author |
Leibundgut, C.; Maloszewski, P.; Külls, C. |
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Title |
Tracers in Hydrology |
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Book Whole |
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Year |
2009 |
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1. Ed. |
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John Wiley & Sons, Ltd |
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THL @ christoph.kuells @ Leibundgut2009tracers |
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37 |
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Morin, E.; Grodek, T.; Dahan, O.; Benito, G.; Külls, C.; Jacoby, Y.; Van Langenhove, G.; Seely, M.; Enzel, Y. |
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Title |
Flood routing and alluvial aquifer recharge along the ephemeral arid Kuiseb River, Namibia |
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Year |
2009 |
Publication |
Journal of Hydrology |
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368 |
Issue |
1-4 |
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262-275 |
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Elsevier |
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THL @ christoph.kuells @ Morin2009flood |
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26 |
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