Spatial variability of soil ~(137)Cs in the South Caspian region

摘要

In a comprehensive program of environmental radioactivity survey in South Caspian region,~(137)Cs inventories in soil has been measured at more than 50 sites in the Iranian northern province of Guilan. This has been the first wide-range survey of soil radionuclide inventories in the narrow band sensitive ecosystem of south Caspian shore. Radioactivity measurements were carried out using HPGe gamma-spectrometry system. The activity concentration of ~(137)Cs in surface soil exhibits a mean value of 17.6±9.4 Bq kg~(-1), with a range of 2.3-41.7 Bq kg~(-1). In many sites, split-level sampling method has been applied down to a depth of 20 cm. There were found generally two profiles. Most profiles exhibit a negative exponential distribution, while others revealed a clear subsurface peak in 5-10-cm layer. Cesium deposition in the study area has been estimated to be in the range of 0.38-2.9 kBq m~(-2) with a mean value of 1.7 kBq m~(-2). Distribution patterns of ~(137)Cs concentration levels and deposition values have been estimated using Kriging interpolation method. Observed hotspots in deposition pattern coincide with areas of higher precipitation.