Continuous measurements of radon content in groundwater on the volcanic site of “Piton de la fournaise” (Island of Reunion, France)

In the framework of the “R.E.M.M.I.” programme (French programme to study the ship relation between water and magma in intertropical environment), different physical and chemical parameters (radon level, conductivity, pH, CO2 level, helium level, temperature) are monitored in the drainage waters of the “Tunnel de la Riviere de l'Est” in order to correlate their variations with the stress in the volcanic chain of the “Piton de la Fournaise”. In a first period of experimentation, during the dry season, the radon concentrations in water have been measured by nuclear track detectors (LR115). In a second field session, during the wet season, a complementary technique has been added: a continuous measurement with a portable proportional counter. The radon measurements and the other results suggest potential for continuous monitoring, through various time steps of the annual cycle likely to be indicators of volcanic activity. This second phase should begin in 1992, September in a new European Programme.