Boulyga Sergei F, Heumann Klaus G
Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University Mainz, Duesbergweg 10-14, 55099 Mainz, Germany.
J Environ Radioact. 2006;88(1):1-10. doi: 10.1016/j.jenvrad.2005.12.007. Epub 2006 Feb 28.
A method by inductively coupled plasma mass spectrometry (ICP-MS) was developed which allows the measurement of (236)U at concentration ranges down to 3 x 10(-14)g g(-1) and extremely low (236)U/(238)U isotope ratios in soil samples of 10(-7). By using the high-efficiency solution introduction system APEX in connection with a sector-field ICP-MS a sensitivity of more than 5,000 counts fg(-1) uranium was achieved. The use of an aerosol desolvating unit reduced the formation rate of uranium hydride ions UH(+)/U(+) down to a level of 10(-6). An abundance sensitivity of 3 x 10(-7) was observed for (236)U/(238)U isotope ratio measurements at mass resolution 4000. The detection limit for (236)U and the lowest detectable (236)U/(238)U isotope ratio were improved by more than two orders of magnitude compared with corresponding values by alpha spectrometry. Determination of uranium in soil samples collected in the vicinity of Chernobyl nuclear power plant (NPP) resulted in that the (236)U/(238)U isotope ratio is a much more sensitive and accurate marker for environmental contamination by spent uranium in comparison to the (235)U/(238)U isotope ratio. The ICP-MS technique allowed for the first time detection of irradiated uranium in soil samples even at distances more than 200 km to the north of Chernobyl NPP (Mogilev region). The concentration of (236)U in the upper 0-10 cm soil layers varied from 2 x 10(-9)g g(-1) within radioactive spots close to the Chernobyl NPP to 3 x 10(-13)g g(-1) on a sampling site located by >200 km from Chernobyl.
开发了一种通过电感耦合等离子体质谱法（ICP-MS）的方法，该方法能够测量土壤样品中浓度低至3×10⁻¹⁴ gg⁻¹的²³⁶U以及低至10⁻⁷的极低²³⁶U/²³⁸U同位素比。通过将高效溶液引入系统APEX与扇形场ICP-MS联用，实现了对铀的灵敏度超过5000计数 fg⁻¹。使用气溶胶去溶剂单元将氢化铀离子UH⁺/U⁺的形成速率降低到10⁻⁶的水平。在质量分辨率为4000时，²³⁶U/²³⁸U同位素比测量的丰度灵敏度为3×10⁻⁷。与α光谱法的相应值相比，²³⁶U的检测限和最低可检测²³⁶U/²³⁸U同位素比提高了两个多数量级。对切尔诺贝利核电站（NPP）附近采集的土壤样品中的铀进行测定，结果表明，与²³⁵U/²³⁸U同位素比相比，²³⁶U/²³⁸U同位素比是用于指示乏铀对环境污染的更为灵敏和准确的标志物。ICP-MS技术首次使得即使在距离切尔诺贝利核电站以北200多公里（莫吉廖夫地区）的土壤样品中也能检测到辐照铀。在切尔诺贝利核电站附近放射性点内，0-10厘米上层土壤中²³⁶U的浓度在2×10⁻⁹ gg⁻¹之间变化，而在距离切尔诺贝利超过200公里的采样点上，该浓度为3×10⁻¹³ gg⁻¹。
