SPATIAL AND TEMPORAL VARIATIONS IN THE LEVELS OF CESIUM IN THE NORTH WESTERN MEDITERRANEAN SEAWATER (1985-1986) Calmet D., Fernandez J.M., Maunier P., Baron Y. Commissariat i l'Energie Atomique Institut de Protection et de Surete Nucleaire Departement d'Etudes et de Recherches en Securite Service d'Etudes et de Recherches sur l'Environnement Station Marine de TOULON BP n*330 83507 LA SEYNE sur MER France ABSTRACT The explosion at the Chernobyl 4 reactor led to the discharge into the atmosphere of 137Cs, the fallout was clearly discernible in the surface waters of the north western part of the Mediterranean coast, although there was no significant health hazard. This radioelement was used as a tracer to plot the stratification and dispersal of water from the Rhone at local and regional levels. It appears to cross the Golfe du Lion along a north east - south west axis. Vertical salinity and temperature profiles plotted with a CTD probe enabled a distinction to be made between the various masses of water present in the Golfe du Lion. There is a difference in the levels of 137Cs activity in the surface and deep water, as measured at reference points. In September 1986, the surface water only showed traces to a depth of 50 m, whereas the whole of the continental shelf water showed traces in December 1986. Outside the continental shelf at the same period, there was no noticeable increase in the 137Cs levels in water at greater depths. INTRODUCTION Since 1977, the Commissariat & l'Energie Atomique's Environmental Studies and Research Service at the TOULON Marine Station has been working on the processes involved in the dispersal of natural or anthropogenic radioelements in the Mediterranean sea, as part of a general research programme (RADMED programme , from RADioactivity and MEDiterranean sea). Samples of seawater are taken annually from the north west Mediterranean basin. Until the first three months of 1986, the results were largely used to monitor the changes in l 37Cs isotopes levels in the water from atmospheric fallout as a result of weapons testing between 1955 and 1979, in the northern hemisphere (1). Unlike the latter type of fallout, which is referred to as global, the explosion at the Chernobyl reactor on 26 April 1986 led to the release of radioelements at

DOI link for SPATIAL AND TEMPORAL VARIATIONS IN THE LEVELS OF CESIUM IN THE NORTH WESTERN MEDITERRANEAN SEAWATER (1985-1986) Calmet D., Fernandez J.M., Maunier P., Baron Y. Commissariat i l'Energie Atomique Institut de Protection et de Surete Nucleaire Departement d'Etudes et de Recherches en Securite Service d'Etudes et de Recherches sur l'Environnement Station Marine de TOULON BP n*330 83507 LA SEYNE sur MER France ABSTRACT The explosion at the Chernobyl 4 reactor led to the discharge into the atmosphere of 137Cs, the fallout was clearly discernible in the surface waters of the north western part of the Mediterranean coast, although there was no significant health hazard. This radioelement was used as a tracer to plot the stratification and dispersal of water from the Rhone at local and regional levels. It appears to cross the Golfe du Lion along a north east - south west axis. Vertical salinity and temperature profiles plotted with a CTD probe enabled a distinction to be made between the various masses of water present in the Golfe du Lion. There is a difference in the levels of 137Cs activity in the surface and deep water, as measured at reference points. In September 1986, the surface water only showed traces to a depth of 50 m, whereas the whole of the continental shelf water showed traces in December 1986. Outside the continental shelf at the same period, there was no noticeable increase in the 137Cs levels in water at greater depths. INTRODUCTION Since 1977, the Commissariat & l'Energie Atomique's Environmental Studies and Research Service at the TOULON Marine Station has been working on the processes involved in the dispersal of natural or anthropogenic radioelements in the Mediterranean sea, as part of a general research programme (RADMED programme , from RADioactivity and MEDiterranean sea). Samples of seawater are taken annually from the north west Mediterranean basin. Until the first three months of 1986, the results were largely used to monitor the changes in l 37Cs isotopes levels in the water from atmospheric fallout as a result of weapons testing between 1955 and 1979, in the northern hemisphere (1). Unlike the latter type of fallout, which is referred to as global, the explosion at the Chernobyl reactor on 26 April 1986 led to the release of radioelements at

SPATIAL AND TEMPORAL VARIATIONS IN THE LEVELS OF CESIUM IN THE NORTH WESTERN MEDITERRANEAN SEAWATER (1985-1986) Calmet D., Fernandez J.M., Maunier P., Baron Y. Commissariat i l'Energie Atomique Institut de Protection et de Surete Nucleaire Departement d'Etudes et de Recherches en Securite Service d'Etudes et de Recherches sur l'Environnement Station Marine de TOULON BP n*330 83507 LA SEYNE sur MER France ABSTRACT The explosion at the Chernobyl 4 reactor led to the discharge into the atmosphere of 137Cs, the fallout was clearly discernible in the surface waters of the north western part of the Mediterranean coast, although there was no significant health hazard. This radioelement was used as a tracer to plot the stratification and dispersal of water from the Rhone at local and regional levels. It appears to cross the Golfe du Lion along a north east - south west axis. Vertical salinity and temperature profiles plotted with a CTD probe enabled a distinction to be made between the various masses of water present in the Golfe du Lion. There is a difference in the levels of 137Cs activity in the surface and deep water, as measured at reference points. In September 1986, the surface water only showed traces to a depth of 50 m, whereas the whole of the continental shelf water showed traces in December 1986. Outside the continental shelf at the same period, there was no noticeable increase in the 137Cs levels in water at greater depths. INTRODUCTION Since 1977, the Commissariat & l'Energie Atomique's Environmental Studies and Research Service at the TOULON Marine Station has been working on the processes involved in the dispersal of natural or anthropogenic radioelements in the Mediterranean sea, as part of a general research programme (RADMED programme , from RADioactivity and MEDiterranean sea). Samples of seawater are taken annually from the north west Mediterranean basin. Until the first three months of 1986, the results were largely used to monitor the changes in l 37Cs isotopes levels in the water from atmospheric fallout as a result of weapons testing between 1955 and 1979, in the northern hemisphere (1). Unlike the latter type of fallout, which is referred to as global, the explosion at the Chernobyl reactor on 26 April 1986 led to the release of radioelements at