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| Titel |
Combining boron isotopes and carbamazepine to monitor artificial recharge (southern Mediterranean) |
| VerfasserIn |
Lise Cary, Catherine Guerrot, Joel Casanova |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250100827
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| Publikation (Nr.) |
 EGU/EGU2014-16828.pdf |
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| Zusammenfassung |
| The groundwater resources of coastal areas are highly vulnerable, being located either in
complex hydrogeological structures or in local shallow aquifers where water stress and salt
water intrusion occur under the multiple constraints governed by increasing anthropogenic
pressures and climatic conditions. Yet, recent integrated water resource planning
often relies on alternative water supplies. In order to limit seawater intrusion in an
agricultural overexploited watershed and to ensure water availability, managed aquifer
recharge with treated wastewater was settled in the Korba aquifer on the east coast of
Tunisia.
Water quality monitoring was implemented in order to determine the different system
components and to trace the effectiveness of the artificial recharge. Groundwater samples
taken from recharge control piezometers and surrounding farm wells were analyzed for their
chemical contents, for their boron isotopes, a proven tracer of groundwater salinization and
domestic sewage, and their carbamazepine content, an anti-epileptic known to pass
through wastewater treatment and so recognized as a pertinent tracer of wastewater
contamination.
The aquifer system is constituted by the superficial and shallow Plio-Quaternary
formations and by the deeper Miocene units which constitute its basement. Marine
Pliocene sediments display interbedded sandstone-sand-marl topped with variably
clayey sandstone. Quaternary deposits are mainly made of fossiliferous carbonated
sandstones.
The system equilibrium was permanently disturbed by the different temporal dynamics of
continuous processes such as cation exchange, and by threshold processes linked to
oxidation-reductive conditions. The boron isotopic compositions of groundwaters displayed a
significant variability (10 - 45 ) and significantly shifted back-and-forth due to mixing
with end-members of various origins. Under the variable contribution of meteoric
recharge, the Plio-Quaternary groundwater was subject to seawater intrusion that
locally induced high δ11B values superior to the seawater signature (δ11B > 39
o no carbamazepine). The managed recharge water (δ11B of 10.7-13.8 ) was
brackish and of poor quality with a carbamazepine content showing a large short term
variability with an average daily level of 328 ± 61 ng/L. A few piezometers in the
vicinity of the recharge site gradually acquired a B isotopic composition close to the
wastewater signature with increasing carbamazepine contents (from 20 to 910 ng/L). The
combination of boron isotopic signatures with boron and carbamazepine contents can be a
useful tool to assess sources and mixing of treated wastewaters in groundwaters. |
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