Assessment of the global fallout of plutonium isotopes and americium-241 in the soil of the central region of Saudi Arabia

A radiochemical technique for determination of plutonium isotopes and Am-241 in soil samples is tested against IAEA-standard reference materials to determine its accuracy and precision for reliable results. The technique is then used in the investigation of topsoil samples, collected from the natural environment of the central region of Saudi Arabia, to assess the effect of fallout accumulation of these radionuclides in the region. Plutonium and americium were sequentially separated from all other components of the sample by anion-exchange chromatography and co-precipitated with Nd3+ as fluorides. The precipitates were mounted on membrane filters and measured using a high-resolution a-spectrometer. The results of the analysis of the reference materials showed satisfactory sensitivity and precision of the technique. The results of the analyzed soil samples show activity levels ranging from <LLD to 0.089 and from <LLD to 0.50 Bq/kg for Pu-238 and Pu239+240, respectively. Am-241 levels ranged from <LLD to 0.49Bq/kg. Pu-238/Pu239+240 and Am-241/Pu239+240 activity ratios ranged from 0 to 0.216 and 0.3-1.23, respectively. A discussion based on the observed data is presented. (C) 2001 Elsevier Science Ltd. All rights reserved.