| Records |
| Author |
Schwiede, M.; Duijnisveld, W.H.M.; Böttcher, J. |
| 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 |
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. |
| Address |
|
| Corporate Author |
|
Thesis |
|
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title  |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| 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 |
| Permanent link to this record |
| |
|
| |
| Author |
Vushe, A.; Amutenya, M. |
| Title |
Investigating nitrate retention capacity, elementary and mineral composition of Kalahari sandy soils at Mashare farm in Namibia, Okavango river basin |
Type |
Journal Article |
| Year |
2019 |
Publication |
Scientific African |
Abbreviated Journal |
|
| Volume |
6 |
Issue |
|
Pages |
00193 |
| Keywords |
Irrigated field, Cultivated Kalahari sandy soil, Leaching, Nitrate retention capacity, Quartz mineral, Water saturated |
| 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. |
| Address |
|
| Corporate Author |
|
Thesis |
|
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
2468-2276 |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
no |
| Call Number |
THL @ christoph.kuells @ VUSHE2019e00193 |
Serial |
277 |
| Permanent link to this record |
| |
|
| |
| Author |
Heaton, T.H.E. |
| Title |
Sources of the nitrate in phreatic groundwater in the western Kalahari |
Type |
Journal Article |
| Year |
1984 |
Publication |
Journal of Hydrology |
Abbreviated Journal |
|
| Volume |
67 |
Issue |
1 |
Pages |
249-259 |
| Keywords |
|
| Abstract |
Elevated levels of nitrate occur in phreatic groundwater in the western Kalahari, Namibia. Nitrate in water containing 0.4–3.1 meq NO−3l−1, of widespread occurrence, has δ15N values in the range +4.9 to +8.0‰, suggesting natural derivation from the soil. The sporadic occurrence of very high levels of nitrate (> 4 meq NO−3l−1), which has δ15N between +9.3 to +18.7‰, reflects pollution derived from animal waste. The importance of considering the possible isotopic effects of denitrification, and the significance of leaching in the nitrogen budget of the Kalahari soil, are also discussed. |
| Address |
|
| Corporate Author |
|
Thesis |
|
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
0022-1694 |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
no |
| Call Number |
THL @ christoph.kuells @ Heaton1984249 |
Serial |
278 |
| Permanent link to this record |
| |
|
| |
| Author |
Stone, A.E.C.; Edmunds, W.M. |
| Title |
Naturally-high nitrate in unsaturated zone sand dunes above the Stampriet Basin, Namibia |
Type |
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). |
| Address |
|
| Corporate Author |
|
Thesis |
|
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
0140-1963 |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
no |
| Call Number |
THL @ christoph.kuells @ Stone201441 |
Serial |
279 |
| Permanent link to this record |
| |
|
| |
| Author |
Vogel, J.C.; Talma, A.S.; Heaton, T.H.E. |
| Title |
Gaseous nitrogen as evidence for denitrification in groundwater |
Type |
Journal Article |
| Year |
1981 |
Publication |
Journal of Hydrology |
Abbreviated Journal |
|
| Volume |
50 |
Issue |
|
Pages |
191-200 |
| Keywords |
|
| Abstract |
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. |
| Address |
|
| Corporate Author |
|
Thesis |
|
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
0022-1694 |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
no |
| Call Number |
THL @ christoph.kuells @ Vogel1981191 |
Serial |
280 |
| Permanent link to this record |
| |
|
| |
| Author |
Wilson, G.B.; McNeill, G.W. |
| Title |
Noble gas recharge temperatures and the excess air component |
Type |
Journal Article |
| Year |
1997 |
Publication |
Applied Geochemistry |
Abbreviated Journal |
|
| Volume |
12 |
Issue |
6 |
Pages |
747-762 |
| Keywords |
|
| Abstract |
The calculation of a groundwater recharge temperature based on the dissolved concentrations of Ne, Ar, Kr and Xe requires a correction for noble gas supersaturation due to excess air entrainment. This entrainment is commonly attributed to the recharge process or to air contamination at the wellhead during sample collection. With the exception of some local studies, most work has concentrated on interpretation of the recharge temperature or quantification of the radiogenic content for palaeoclimatic and dating purposes. The magnitude and source of the excess air is not directly relevant to these studies and so is often ignored. In this work, excess air Ne and other data have been calculated from new and published noble gas data sets for several groundwater systems. For younger groundwaters which have been recharged under one broad climatic regime, the amount of air entrainment increases according to lithology in the order granites, sandstones and limestones respectively. A negative correlation between precipitation and excess air entrainment is identified in at least one aquifer, and some of the mechanisms which may influence the entrainment process are discussed. |
| Address |
|
| Corporate Author |
|
Thesis |
|
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
0883-2927 |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
no |
| Call Number |
THL @ christoph.kuells @ Wilson1997747 |
Serial |
281 |
| Permanent link to this record |
| |
|
| |
| Author |
Heaton, T.H.E.; Talma, A.S.; Vogel, J.C. |
| Title |
Origin and history of nitrate in confined groundwater in the western Kalahari |
Type |
Journal Article |
| Year |
1983 |
Publication |
Journal of Hydrology |
Abbreviated Journal |
|
| Volume |
62 |
Issue |
1 |
Pages |
243-262 |
| Keywords |
|
| Abstract |
Data are presented for nitrate, dinitrogen and argon concentrations and 15N14N ratios in groundwater, with radiocarbon ages up to 40,000 yr. for three confined sandstone aquifers in the western Kalahari of South West Africa/Namibia. The nitrate is probably generated within the soil of the recharge areas, and its production rate during the period 3000-40,000 B.P. has remained between 0.5 and 1.6 meq NO−3l−1 of recharge water, with ° 15N between + 4 and + 8‰. Variations in the amount of nitrate and of “excess air” in groundwater recharge are found, and can only reflect changes in the environmental conditions during recharge. They must therefore be caused by the climatic changes that have taken place during the past 25,000 yr. |
| Address |
|
| Corporate Author |
|
Thesis |
|
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
0022-1694 |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
no |
| Call Number |
THL @ christoph.kuells @ Heaton1983243 |
Serial |
282 |
| Permanent link to this record |
| |
|
| |
| Author |
Doulgeris, C.; Tziritis, E.; Pisinaras, V.; Panagopoulos, A.; Külls, C. |
| Title |
Prediction of seawater intrusion to coastal aquifers based on non-dimensional diagrams |
Type |
Conference Article |
| Year |
2020 |
Publication |
EGU Geophysical Abstracts |
Abbreviated Journal |
|
| Volume |
|
Issue |
|
Pages |
4073 |
| Keywords |
|
| Abstract |
|
| Address |
|
| Corporate Author |
|
Thesis |
|
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
|
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
no |
| Call Number |
THL @ christoph.kuells @ Doulgeris2020prediction |
Serial |
41 |
| Permanent link to this record |
| |
|
| |
| Author |
Leibundgut, C.; Maloszewski, P.; Külls, C. |
| Title |
Tracers in Hydrology |
Type |
Book Whole |
| Year |
2009 |
Publication |
|
Abbreviated Journal |
|
| Volume |
|
Issue |
1. Ed. |
Pages |
|
| Keywords |
|
| Abstract |
|
| Address |
|
| Corporate Author |
|
Thesis |
|
| Publisher |
John Wiley & Sons, Ltd |
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
|
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
no |
| Call Number |
THL @ christoph.kuells @ Leibundgut2009tracers |
Serial |
37 |
| Permanent link to this record |
| |
|
| |
| Author |
Külls, C. |
| Title |
Groundwater of the North-Western Kalahari, Namibia: estimation of recharge and quantification of the flow system |
Type |
Book Whole |
| Year |
2001 |
Publication |
Hydrogeologie und Umwelt |
Abbreviated Journal |
|
| Volume |
|
Issue |
|
Pages |
|
| Keywords |
|
| Abstract |
|
| Address |
|
| Corporate Author |
|
Thesis |
Doctoral thesis |
| Publisher |
Hydrogeologie und Umwelt |
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
|
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
no |
| Call Number |
THL @ christoph.kuells @ Kuells2003groundwater |
Serial |
38 |
| Permanent link to this record |
