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Vushe, A.; Amutenya, M. |
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Title |
Investigating nitrate retention capacity, elementary and mineral composition of Kalahari sandy soils at Mashare farm in Namibia, Okavango river basin |
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Journal Article |
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Year |
2019 |
Publication |
Scientific African |
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Volume |
6 |
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Pages |
00193 |
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Keywords |
Irrigated field, Cultivated Kalahari sandy soil, Leaching, Nitrate retention capacity, Quartz mineral, Water saturated |
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Abstract |
Kalahari sands which cover a large part of Southern Africa and extend into Central Africa are infertile and marginal soils for intensive agriculture. Therefore, high nitrogen fertilisation rates may degrade ecosystems of rivers with catchments covered by the Kalahari sands. A study on Mashare Farm located in the Okavango River basin showed that irrigated Kalahari sandy soils had a nitrate retention capacity, which enabled the soil to resist nitrate leaching in water saturated conditions. The irrigated soils were modified by agricultural activities; hence this study investigated if uncultivated and cultivated Kalahari sand soils had similar nitrate retention properties. The elementary composition of the soils was investigated for obtaining an insight into chemical properties that may be causing the nitrate retention capacity. A permeameter was used to leach out nitrates from irrigated and uncultivated soil samples, and nitrate concentrations were measured on the leaching effluent from the permeameter. Elemental analysis was done on the cultivated and the uncultivated soil samples using a Scanning Electron Microscope, a portable X-Ray Fluorescence analyzer, and an X-Ray Diffraction machine, and the later was also used for crystalline structure analyses. Sieve analyses confirmed that the Mashare’s cultivated and uncultivated topsoils were similar, and both were similar to Botswana Kalahari topsoil. The irrigated and cultivated subsoil had a higher average nitrate retention capacity of 76% compared to 73% for the uncultivated subsoil. Both samples had the same elements, although the proportions were different. Both soil samples were dominated by a quartz mineral, but the field soil had traces of palygorskite. The presence of aluminum and transition metals outside the minerals structure, but as coatings on the quartz sand grains enhanced nitrate retention capacity properties of the Kalahari sand soils. |
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2468-2276 |
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THL @ christoph.kuells @ VUSHE2019e00193 |
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277 |
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Author |
Stone, A.E.C.; Edmunds, W.M. |
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Title |
Naturally-high nitrate in unsaturated zone sand dunes above the Stampriet Basin, Namibia |
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Journal Article |
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Year |
2014 |
Publication |
Journal of Arid Environments |
Abbreviated Journal |
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105 |
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41-51 |
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Kalahari, Namibia, Nitrate in the unsaturated zone, Stampriet Basin, Transboundary basin, Unsaturated zone recharge |
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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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0140-1963 |
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THL @ christoph.kuells @ Stone201441 |
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279 |
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Vogel, J.C.; Talma, A.S.; Heaton, T.H.E. |
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Title |
Gaseous nitrogen as evidence for denitrification in groundwater |
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Journal Article |
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Year |
1981 |
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Journal of Hydrology |
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50 |
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191-200 |
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By investigating the nitrate, oxygen, nitrogen and argon concentrations and 15N14N ratios in artesian groundwater with radiocarbon ages ranging up to 27,000 yr. a process of very slow denitrification in a confined aquifer is demonstrated. The calculated nitrogenisotope fractionation factor associated with this reaction is comparable to that reported for bacterial cultures in vitro and in vivo. |
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0022-1694 |
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THL @ christoph.kuells @ Vogel1981191 |
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280 |
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Author |
Doulgeris, C.; Tziritis, E.; Pisinaras, V.; Panagopoulos, A.; Külls, C. |
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Title |
Prediction of seawater intrusion to coastal aquifers based on non-dimensional diagrams |
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Conference Article |
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2020 |
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EGU Geophysical Abstracts |
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4073 |
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THL @ christoph.kuells @ Doulgeris2020prediction |
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41 |
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Author |
Külls, C. |
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Title |
Groundwater of the North-Western Kalahari, Namibia: estimation of recharge and quantification of the flow system |
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Book Whole |
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2001 |
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Hydrogeologie und Umwelt |
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Doctoral thesis |
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Hydrogeologie und Umwelt |
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THL @ christoph.kuells @ Kuells2003groundwater |
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38 |
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Döll, P.; Krol, M.; Fuhr, D.; Gaiser, T.; Herfort, J.; Höynck, S.; Jaeger, A.; Külls, C.; Mendiondo, E.M.; Printz, A.; others |
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Title |
Integrated scenarios of regional development in Ceará and Piauí |
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2003 |
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Global Change and Regional Impacts |
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19-41 |
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Springer, Berlin, Heidelberg |
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THL @ christoph.kuells @ Doll2003integrated |
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39 |
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Voerkelius, S.; Külls, C.; Santiago, M.M.F.; Frischkorn, H.; dos Santos Semrau, L.A.; Heinrichs, G.; Gil, M.M.L. |
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Investigations on water management and water quality in Picos/PI and Tauá/CE |
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Book Chapter |
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2003 |
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Global change and regional impacts |
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173-184 |
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Springer, Berlin, Heidelberg |
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THL @ christoph.kuells @ Voerkelius2003investigations |
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40 |
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Author |
Külls, C.; Leibundgut, C.; Schwarz, U.; Schick, A.P. |
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Title |
Channel infiltration study using dye tracers |
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1995 |
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IAHS Publications-Series of Proceedings and Reports-Intern Assoc Hydrological Sciences |
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232 |
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429-436 |
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Wallingford [Oxfordshire]: IAHS, 1981- |
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THL @ christoph.kuells @ Kuells1995channel |
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36 |
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Author |
Zagana, E.; Külls, C.; Udluft, P. |
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Title |
Der Wasserhaushalt des Aliakmonas |
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2000 |
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Vom Wasser |
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94 |
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29-39 |
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THL @ christoph.kuells @ Zagana2000saa |
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34 |
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Külls, C.; Adar, E.M.; Udluft, P. |
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Title |
Tracer Studies and Modelling of Regional Groundwater Systems-Resolving patterns of groundwater flow by inverse hydrochemical modelling in a semiarid Kalahari basin |
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Journal Article |
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2000 |
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IAHS Publications-Series of Proceedings and Reports-Intern Assoc Hydrological Sciences |
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262 |
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447-452 |
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Wallingford [Oxfordshire]: IAHS, 1981- |
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THL @ christoph.kuells @ Kuells2006 |
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31 |
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