Details
| Original language | English |
|---|---|
| Pages (from-to) | 312-324 |
| Number of pages | 13 |
| Journal | Isotopes in Environmental and Health Studies |
| Volume | 46 |
| Issue number | 3 |
| Publication status | Published - 2010 |
Abstract
In the framework of the investigation of enrichment processes of nitrate in groundwater of the Kalahari of Botswana near Serowe, recharge processes were investigated. The thick unsaturated zone extending to up to 100 m of mostly unconsolidated sediments and very low recharge rates pose a serious challenge to study solute transport related to infiltration and recharge processes, as this extends past the conventional depths of soil scientific investigations and is difficult to describe using evidence from the groundwater due to the limitations imposed by available tracers. To determine the link between nitrate in the vadose zone and in the uppermost groundwater, sediment from the vadose zone was sampled up to a depth of 15-20 m (in one case also to 65 m) on several sites with natural vegetation in the research area. Among other parameters, sediment and water were analysed to determine chloride and nitrate concentration depth profiles. Using the chloride mass balance method, an estimation of groundwater infiltration rates produced values of 0.2-4 mma-1. The uncertainty of these values is, however, high. Because of the extreme thickness of the vadose zone, the travel time in the unsaturated zone might reach extreme values of up to 500 years and more. For investigations using groundwater, we applied the chlorofluorocarbons CFC-113, CFC-12, sulphur hexafluoride (SF6) and tritium to identify potential recharge, and found indications for some advective transport of the CFCs and SF6, which we accounted for as constituting potential active localised recharge. In our contribution, we show the potential and limitations of the applied methods to determine groundwater recharge and coupled solute transport in semi-arid settings, and compare travel time ranges derived from soil science and groundwater investigations.
Keywords
- Aquifer, Botswana, CFC, Helium-3, Hydrogen-3, Infiltration, Isotope ecology, Isotope hydrology, Kalahari, Recharge, Soil water, Sulphur hexafluoride
ASJC Scopus subject areas
- Environmental Science(all)
- Environmental Chemistry
- Environmental Science(all)
- General Environmental Science
- Chemistry(all)
- Inorganic Chemistry
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In: Isotopes in Environmental and Health Studies, Vol. 46, No. 3, 2010, p. 312-324.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Linking chloride mass balance infiltration rates with chlorofluorocarbon and SF6 groundwater dating in semi-arid settings
T2 - Potential and limitations
AU - Stadler, Susanne
AU - Osenbrück, Karsten
AU - Duijnisveld, Wilhelmus H.M.
AU - Schwiede, Martin
AU - Böttcher, Jürgen
N1 - Copyright: Copyright 2011 Elsevier B.V., All rights reserved.
PY - 2010
Y1 - 2010
N2 - In the framework of the investigation of enrichment processes of nitrate in groundwater of the Kalahari of Botswana near Serowe, recharge processes were investigated. The thick unsaturated zone extending to up to 100 m of mostly unconsolidated sediments and very low recharge rates pose a serious challenge to study solute transport related to infiltration and recharge processes, as this extends past the conventional depths of soil scientific investigations and is difficult to describe using evidence from the groundwater due to the limitations imposed by available tracers. To determine the link between nitrate in the vadose zone and in the uppermost groundwater, sediment from the vadose zone was sampled up to a depth of 15-20 m (in one case also to 65 m) on several sites with natural vegetation in the research area. Among other parameters, sediment and water were analysed to determine chloride and nitrate concentration depth profiles. Using the chloride mass balance method, an estimation of groundwater infiltration rates produced values of 0.2-4 mma-1. The uncertainty of these values is, however, high. Because of the extreme thickness of the vadose zone, the travel time in the unsaturated zone might reach extreme values of up to 500 years and more. For investigations using groundwater, we applied the chlorofluorocarbons CFC-113, CFC-12, sulphur hexafluoride (SF6) and tritium to identify potential recharge, and found indications for some advective transport of the CFCs and SF6, which we accounted for as constituting potential active localised recharge. In our contribution, we show the potential and limitations of the applied methods to determine groundwater recharge and coupled solute transport in semi-arid settings, and compare travel time ranges derived from soil science and groundwater investigations.
AB - In the framework of the investigation of enrichment processes of nitrate in groundwater of the Kalahari of Botswana near Serowe, recharge processes were investigated. The thick unsaturated zone extending to up to 100 m of mostly unconsolidated sediments and very low recharge rates pose a serious challenge to study solute transport related to infiltration and recharge processes, as this extends past the conventional depths of soil scientific investigations and is difficult to describe using evidence from the groundwater due to the limitations imposed by available tracers. To determine the link between nitrate in the vadose zone and in the uppermost groundwater, sediment from the vadose zone was sampled up to a depth of 15-20 m (in one case also to 65 m) on several sites with natural vegetation in the research area. Among other parameters, sediment and water were analysed to determine chloride and nitrate concentration depth profiles. Using the chloride mass balance method, an estimation of groundwater infiltration rates produced values of 0.2-4 mma-1. The uncertainty of these values is, however, high. Because of the extreme thickness of the vadose zone, the travel time in the unsaturated zone might reach extreme values of up to 500 years and more. For investigations using groundwater, we applied the chlorofluorocarbons CFC-113, CFC-12, sulphur hexafluoride (SF6) and tritium to identify potential recharge, and found indications for some advective transport of the CFCs and SF6, which we accounted for as constituting potential active localised recharge. In our contribution, we show the potential and limitations of the applied methods to determine groundwater recharge and coupled solute transport in semi-arid settings, and compare travel time ranges derived from soil science and groundwater investigations.
KW - Aquifer
KW - Botswana
KW - CFC
KW - Helium-3
KW - Hydrogen-3
KW - Infiltration
KW - Isotope ecology
KW - Isotope hydrology
KW - Kalahari
KW - Recharge
KW - Soil water
KW - Sulphur hexafluoride
UR - http://www.scopus.com/inward/record.url?scp=77956666532&partnerID=8YFLogxK
U2 - 10.1080/10256016.2010.508124
DO - 10.1080/10256016.2010.508124
M3 - Article
C2 - 20812119
AN - SCOPUS:77956666532
VL - 46
SP - 312
EP - 324
JO - Isotopes in Environmental and Health Studies
JF - Isotopes in Environmental and Health Studies
SN - 1025-6016
IS - 3
ER -