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Author Külls, C.
Title Ecohydrological principles in economic models of water resources in drylands and desert restoration Type (down) Miscellaneous
Year 2014 Publication UNCCD, 2nd Scient. Conf. Abbreviated Journal
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Call Number THL @ christoph.kuells @ Kuells2014ecohydrological Serial 68
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Author Hamutoko, J.; Mapani, B.; Ellmies, R.; Bittner, A.; Külls, C.
Title A fingerprinting method for the identification of uranium sources in alluvial aquifers: An example from the Khan and Swakop Rivers, Namibia Type (down) Journal Article
Year 2014 Publication Physics and Chemistry of the Earth, Parts A/B/C Abbreviated Journal
Volume 72 Issue Pages 34-42
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Publisher Pergamon Place of Publication Editor
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Call Number THL @ christoph.kuells @ Hamutoko2014fingerprinting Serial 19
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Author Müller, M.; Alaoui, A.; Külls, C.; Leistert, H.; Meusburger, K.; Stumpp, C.; Weiler, M.; Alewell, C.
Title Tracking water pathways in steep hillslopes by δ18O depth profiles of soil water Type (down) Journal Article
Year 2014 Publication Journal of hydrology Abbreviated Journal
Volume 519 Issue Pages 340-352
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Publisher Elsevier Place of Publication Editor
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Call Number THL @ christoph.kuells @ Mueller2014tracking Serial 20
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Author Stone, A.E.C.; Edmunds, W.M.
Title Naturally-high nitrate in unsaturated zone sand dunes above the Stampriet Basin, Namibia Type (down) Journal Article
Year 2014 Publication Journal of Arid Environments Abbreviated Journal
Volume 105 Issue Pages 41-51
Keywords Kalahari, Namibia, Nitrate in the unsaturated zone, Stampriet Basin, Transboundary basin, Unsaturated zone recharge
Abstract Elevated groundwater nitrate levels are common in drylands, often in excess of WHO guidelines, with concern for human and animal health. In light of recent attempts to identify nitrate sources in the Kalahari this paper presents the first unsaturated zone (USZ) nitrate profiles and recharge rate estimates for the important transboundary Stampriet Basin, alongside the first rainfall chemistry records. Elevated subsurface nitrate reaches 100–250 and 250–525 mg/L NO3–N, with NO3–N/Cl of 4–12, indicating input above evapotranspiration. Chloride mass balance recharge rates range from 4 to 27 mm/y, indicating a vertical movement of these nitrate pulses toward the water table over multi-decadal timescales. These profiles are sampled from dune crests, away from high concentrations of animals and without termite mounds. Given low-density animal grazing is unlikely to contribute consistent spot-scale nitrate over decades, these profiles give an initial estimate of naturally-produced concentrations. This insight is important for the management of the Stampriet Basin and wider Kalahari groundwater. This study expands our knowledge about elevated nitrate in dryland USZs, demonstrating that it can occur as pulses, probably in response to transient vegetation cover and that it is not limited to long-residence time USZs with very limited downward moisture flux (recharge).
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ISSN 0140-1963 ISBN Medium
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Call Number THL @ christoph.kuells @ stone_naturally-high_2014 Serial 91
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Author Khoury, H.N.; salameh, E.M.; Clark, I.D.
Title Mineralogy and origin of surficial uranium deposits hosted in travertine and calcrete from central Jordan Type (down) Journal Article
Year 2014 Publication Applied Geochemistry Abbreviated Journal
Volume 43 Issue Pages 49-65
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Abstract Secondary uranium encrustations are hosted in thick travertine and calcrete deposits of Pleistocene–Recent age in central Jordan. The central Jordan varicolored marble and travertine are equivalent to the active metamorphic area in Maqarin, north Jordan. More than 100 samples were collected from the outcrops of the varicolored marble, travertine, calcrete, and the yellow uranium encrustations. The secondary yellow encrustations are mainly composed of uranyl vanadate complexes. Tyuyamunite Ca(UO2)2V25+O8·3(H2O)–strelkinite Na2(UO2)2V2O8·6(H2O) solid solution series are the major components and their composition reflects changes in the Ca/Na ratio in solution. Potentially, new vanadium free calcium uranate phases (restricted to the varicolored marble) were identified with CaO:UO3 ratios different from the known mineral vorlanite (CaU6+)O4. Carbon and oxygen isotope data from calcite in the varicolored marble are characterized by Rayleigh-type enrichment in light isotopes associated with release of 13C and 18O enriched CO2 by high temperature decarbonation during combustion of the bituminous marl. Stable isotope results from uranium hosted travertine and calcrete varieties exhibit a wide range in isotopic values, between decarbonated and normal sedimentary carbonate rocks. The depleted δ13C and δ18O values in the travertine are related to the kinetic reaction of atmospheric CO2 with hyperalkaline Ca(OH)2 water. The gradual enrichment of δ13C and δ18O values in the calcrete towards equilibrium with the surrounding environment is related to continuous evaporation during seasonal dry periods. Uranium mineralization in central Jordan resulted from the interplay of tectonic, climatic, hydrologic, and depositional events. The large distribution of surficial uranium occurrences hosted in travertine and calcrete deposits is related to the artesian ascending groundwater that formed extensive lakes along NNW–SSE trending depressions. Fresh groundwater moved upward through the highly fractured phosphate, bituminous marl and varicolored marble to form unusual highly alkaline water (hydroxide–sulfate type) enriched with sensitive redox elements among which were U and V.
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ISSN 0883-2927 ISBN Medium
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Call Number THL @ christoph.kuells @ khoury_mineralogy_2014 Serial 121
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