Dissolved inert gases in three karstic systems in Europe (France and Greece).

Dissolved noble gases (He, Ne, and Ar) and N2 were measured in spring waters from three karstic systems in Europe: Baget and Larzac in France, and Drama in Greece. The content of dissolved gases was higher than those expected for water equilibrated to air at the spring's temperature range (0-15°C) and was related to both the presence of air and He excess. The He isotopic composition reveals: a dominant air and air saturated water origin for the Baget samples, a slight mantle derived He excess for Larzac and a clear crustal He excess for Drama. Although the recording time was limited, the influence of deepest waters enriched in He was more evident during the dry season. Karstic waters are therefore the result of a complex hydrologic circulation of several reservoirs characterized by different water residence times exchanging water mainly during floods.