Radionuclide inventories were measured in soils from different French mountainous areas: Chaıˆne des Puys (Massif Central), Eastern Corsica, Jura, Montagne Noire, Savoie, Vosges and Rhine Valley. 210 Pb soil inventories were used to estimate long-term (475 yr) deposition of submicron aerosols. Whereas 210 Pb total deposition is explained partly by wet deposition, as demonstrated by increase of 210 Pb inventory with annual rainfall; a part of 210 Pb in the soils of higher altitude is caused by orographic depositions. Using measurements of radionuclides coming from nuclear aerial weapon tests ( 137 Cs and Pu isotopes), we were able to estimate the origin of aerosols deposited in high-altitude sites and to confirm the importance of occult deposition and feeder-seeder mechanism. Using a simple mass balance model, we estimate that occult deposition and feeder-seeder mechanisms account to more than 50% of total deposition of 210 Pb and associated submicron aerosols in French altitude sites.

Soil inventories of anthropogenic radionuclides were investigated in altitudinal transects in 2 French regions, Savoie and Montagne Noire. Rain was negligible in these 2 areas the days after the Chernobyl accident. Thus anthropogenic radionuclides are coming hypothetically only from Global Fallout following Atmospheric Nuclear Weapon Tests. This is confirmed by the isotopic signatures ((238)Pu/(239+240)Pu; (137)Cs/(239+240)Pu; and (241)Am/(239+240)Pu) close to Global Fallout value. In Savoie, a peat core age-dated by (210)Pb(ex) confirmed that the main part of deposition of anthropogenic radionuclides occurred during the late sixties and the early seventies. In agreement with previous studies, the anthropogenic radionuclide inventories are well correlated with the annual precipitations. However, this is the first time that a study investigates such a large panel of annual precipitation and therefore of anthropogenic radionuclide deposition. It seems that at high-altitude sites, deposition of artificial radionuclides was higher possibly due to orographic precipitations.

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