| Records |
| 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 |
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| Volume |
67 |
Issue |
1 |
Pages |
249-259 |
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| 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. |
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0022-1694 |
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THL @ christoph.kuells @ Heaton1984249 |
Serial |
278 |
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| 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 |
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| Volume |
50 |
Issue |
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Pages |
191-200 |
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| 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. |
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0022-1694 |
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THL @ christoph.kuells @ Vogel1981191 |
Serial |
280 |
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| 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 |
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| Volume |
12 |
Issue |
6 |
Pages |
747-762 |
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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. |
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0883-2927 |
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| Call Number |
THL @ christoph.kuells @ Wilson1997747 |
Serial |
281 |
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| 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 |
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| Volume |
62 |
Issue |
1 |
Pages |
243-262 |
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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. |
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0022-1694 |
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| Call Number |
THL @ christoph.kuells @ Heaton1983243 |
Serial |
282 |
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