Migration study of radionuclides in a Mediterranean forest soil using synthetic aerosols

Radionuclide migration in a Mediterranean forest was studied in field conditions. Fresh Holm oak leaves were exposed to a synthetic aerosol including 134Cs, 85Sr and 110mAg, and were incubated in the original Holm oak forest in two types of cylinder: (1) cylinders in which the contaminated litter lies directly on the original F layer; (2) cylinders with an exchange resin bag inserted between the contaminated litter and the underlying F layer. The results for 232 days of incubation showed that 134Cs presented an initial rapid leaching period, which corresponded to the fraction extracted with water from the initially contaminated leaves. Further 134Cs release was related to litter decomposition. 85Sr migration was studied for only 76 days, and its behaviour appeared to be similar to 134Cs. Both radionuclides migrated within the litter leachates. After 3 months of incubation, around 70% of the initial 134Cs was transferred to the underlying layers, mainly to the F layer. 134Cs absorbed into the leaves was released at the same rate as K. The 110Ag activity lost from the contaminated litter amounted to around 45% in the open cylinders, from which 15–20% was attributed to the effect of soil faunal activity. The field method proposed proved to be useful in describing radionuclide migration in situ and the mechanisms involved.