Spatial variability of fallout-(137)Cs in the soil of a cultivated field

To obtain information on the spatial variability of fallout (137)Cs in the soil of a small area, the activity concentration of this radionuclide was determined in 100 soil samples, taken along the two diagonals of a cultivated field (150×100 m). The results show that the spatial distribution of (137)Cs in this field is at random. The frequency distribution of the values is skewed to the right, but not log-normal. The median activity concentration observed was 7.45 Bq kg(-1) dry soil, the values ranging from 4.8-15 Bq kg(-1). The spatial variability, as characterized by the relative decile deviation was 26%. If one tolerates for the establishment of baselines of global fallout (137)Cs in the soil an error in the mean activity concentration of 10% (20%) at the 95% confidence level, the minimum number of soil samples to be taken can be estimated as 14 (4). The total deposition of (137)Cs on the soil surface by fallout was determined as 3.3±0.4 kBq m(-2).