 |
| Titel |
Tracking the multiple origins of salinity in three different karstic aquifers (southern France): Sr isotopes constraints. |
| VerfasserIn |
Corinne Le Gal La Salle, Mahmoud Khaska, Joël Lancelot |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250100835
|
| Publikation (Nr.) |
 EGU/EGU2014-16837.pdf |
|
|
|
|
|
| Zusammenfassung |
| Groundwater resources of the Mediterranean area are submitted to a high anthropic pressure
and face a set of major climatic and geological constraints. The potential exploitation of karst
aquifers is still unclear and probably underestimated, but their vulnerability to pollution is
high and potential for salinization in coastal aquifer increases with over exploitation and the
rise of sea level.
In order to trace the origin of salinity in karst aquifers in a Mediterranean coastal
environment, a multi-tracer approach coupling major, specific trace elements and stable
(δ18O, δ2H) and radiogenic (87Sr/86Sr) isotopes was held. Three close sites in southern
France have been studied to investigate a different origin of the salinity.
In the coastal karst aquifer of la Clape (Aude), salinity originated from deep salt water
due to a paleoseawater intrusion followed by water-rock interaction with the carbonate host
rock. On land and off-shore, powerful tertiary sedimentary deep deposits limit the karst
network communications with the seawater. The presence of many faults could be
a contributing factor to the mixing of salt water within the karst water. There it
was shown that the paleoseawater proportions in the aquifer ranged from 0 to 16
%.
Slightly further inland, in another similar karstic aquifer, the source of Oeillal (Aude)
displayed a high salinity. Salinity most surely originated from deep horizons that come to the
surface by a major normal fault where it mixes with karst waters. Deep brines from ancient
meteoric water evolved by water-rock interaction with evaporites in the underlying Keuper
formation. There calculated proportions of salt water into the mixture with karst water varied
between 30 and 40%.
In the third site located on the edge of the seawater shoreline, the simple limestone karst
aquifer of Pliocene in Frontignan (Hérault) was under increasing salinity intrusion of
seawater, which proportions of mixing between seawater and karst water varied from 2 to
4%.
These results highlight the variability of salinity origins in close coastal Mediterranean
karst aquifers and the important contribution of evaporites, deep salty waters and seawater
intrusion. Tools to investigate the origin of water salinity will be highlighted. Water
management of these karstic aquifers must integrate the complex geological constraints. |
|
|
|
|
|
|