Inventory and vertical migration of 90Sr fallout and 137Cs/90Sr ratio in Spanish mainland soils

In this paper the inventory of 90Sr in 34 points distributed along the Spanish peninsular territory is presented. Obtained values range between 173 Bq/m2 and 2047 Bq/m2. From these data set and those 137Cs data obtained in a previous work the 137Cs/90Sr activity ratio has been established, laying this value between 0.9 and 3.6. Also the migration depth of both radionuclides has been analysed obtaining for 137Cs an average value 57% lower than that obtained for 90Sr.Additionally, this paper presents the results obtained in 11 sampling points in which the activity vertical profile has been measured. These profiles have been analysed to state the behaviour of strontium in soils and after, by using a convective–diffusive model, the parameters of the model which governs the vertical migration of 90Sr in the soil, v (apparent convection velocity) and D (apparent diffusion coefficient) have been evaluated. Mean values obtained are 0.20 cm/year and 3.67 cm2/year, respectively.

► Measured 90Sr activity in Spanish mainland, being within a range of [173, 2047] Bq/m2, with a mean value of 793 Bq/m2.
► Compared the migration capacity of 137Cs and 90Sr in the same soils.
► 90Sr shows a unique behaviour tendency in soil.
► The parameters which govern the applied model have been obtained for the analysed profiles.
► Analysed those parameters’ values also reflects this unique tendency.