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| Titel |
Tracing the origin of nitrate accumulation in a deep groundwater reservoir in the Sahara desert using mass dependent and non-mass-dependent isotopic signatures |
| VerfasserIn |
A. Leis, M. Dietzel, R. Abdalla, J. Savarino, M. Böttcher, S. J. Köhler |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250041282
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| Zusammenfassung |
| Accumulation of nitrate in groundwater is a well known problem and mostly due to
anthropogenic activities. However, in desert regions far from any anthropogenic pollution the
accumulation of nitrate in groundwaters has to be related to other processes. In the present
study an integrative hydrogeochemical and isotopic approach is used to identify the origin of
nitrate in the Hasouna basin. The Jabal Hasouna wellfields are located in Libyan desert about
700 kilometers south of Tripoli. In the groundwater samples aqueous major and trace
elements as well as traditional and non-traditional environmental isotopes were
analyzed.
Stable hydrogen and oxygen isotopic composition of the groundwater indicate that the
ancient groundwater was recharged under cooler and more humid climate conditions.
Nitrogen (δ15N) and oxygen isotopes (δ17O, δ18O) of dissolved nitrate as well as sulphur
(δ34S) and oxygen (δ18O) isotopes in sulphate were measured to identify nitrate and sulphate
sources and accumulation mechanisms. Our results indicate that nitrate in groundwater of the
study area is of natural origin. Moreover, all investigated samples yield positive
Î17O values of nitrate, which clearly indicate that every groundwater contains
an individual degree of atmospheric nitrate within dissolved nitrate. Î17O values
are strongly correlated with nitrate concentration, whereas the trend for δ18O is
less diagnostic. A similar but more ambiguous trend can be also found for δ18O of
sulphate.
Our investigations indicate that Î17O signatures of nitrate can be applied as a powerful
tool to trace the origin and fate of nitrate in deep groundwater reservoirs. Involving Î17O
signatures in groundwater studies may provide enhanced understanding of ancient and recent
recharge conditions in arid areas. |
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