Modelling seasonal variations of natural radionuclides in agricultural soils

Estimating activity of natural radionuclides in agricultural soil is very important for the protection of public health because the released radioactivity can enter the food chain. Radioactivity measurements were carried out in two different dates (winter and summer) in agricultural soil using a GRM-260 gamma-ray spectrometer. The study area (100 m x 100 m) was an olive orchard in southern Italy. Measurements were carried out at 361 locations in January and July 2011. At the same locations, soil water content was measured to take into account the effect of soil moisture on radioactivity. A multi-Gaussian approach was used to explore and map the activity of naturally occurring radionuclides and soil water content for both seasons of measurements. The minimum radioactivity values were recorded in winter and the maximum values in summer, probably as a consequence of changes in weather and soil conditions (rainfall, soil moisture, temperature).