Multi-tracer reconnaissance of submarine groundwater discharge along the French Mediterranean coast

Stieglitz, Thomas, van Beek, Pieter, and Souhaut, Marc (2010) Multi-tracer reconnaissance of submarine groundwater discharge along the French Mediterranean coast. In: Abstracts from Radium and Radon Isotapes as Environmental Tracers. p. 20. From: Radium and Radon Conference 2010: Radium and Radon Isotopes as Environmental Tracers, 14 - 19 March 2010, Jerusalem, Israel.

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In order to evaluate the regional distribution of SGD along the French Mediterranean coast, the spatial distribution of radium, radon and salinity was investigated at a number of locations where groundwater was previously known to discharge into coastal waters. Field work was carried out during summer 2009 in the coastal lagoons of Salses-Leucate, La Palme and Tuau, and along the karstic coastline of 'Les Calanques' between Marseille and Cassis. The hydrogeology of the region is dominated by the karstic rocks of the coastal uplands. Mixing of coastal waters region is driven primarily by wind and air pressure changes. Radon and salinity in surface waters were mapped concurrently to obtain an overview of SGD locations and processes, and spot radium samples were collected to study fluxes of SGD, missing relationships with coastal waters and residence times of the lagoon waters. Radon was measured in situ with a surface-towed, continuously recoding multi-detector setup using Durridge Rad7 Radon-in-air monitors. Radium was sampled with managanese fibers by standard methods. Short and long lived isotopes were counted with RADECC delayed coincidence counters and gamma spectrometry in the underground laboratory at Ferrieres (Pyrenees) respectively.

A brief overview of the study sites and results will be presented. For example, in the lagoon of La Palme, the spatial distribution of radionuclides varied dramatically over short period of time, likely associated with wind-driven input of saline groundwater from disused salt evaporation ponds, in addition to be groundwater input from karstic springs. In the Taui lagoon, the well-known submarine freshwater spring 'La Vise' in ca 25m of depth appears to have only a small impact on the radionuclide budget of the lagoon due to a very small flow rate. The Canal Du Midi may be additional source of radon during southerly winds, and small but systematic elevations of radon at typical lagoon salinity in shallow parts of the lagoon suggest the recirculation of seawater there. The residence time of water in the lagoons was found to be in the order of a few days, but varies with wind conditions.

Item ID: 16190
Item Type: Conference Item (Abstract / Summary)
Date Deposited: 05 May 2011 01:06
FoR Codes: 04 EARTH SCIENCES > 0405 Oceanography > 040503 Physical Oceanography @ 100%
SEO Codes: 96 ENVIRONMENT > 9611 Physical and Chemical Conditions of Water > 961102 Physical and Chemical Conditions of Water in Coastal and Estuarine Environments @ 100%
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