Determination of Iodine-129 in twenty soil and sediment reference materials
Dr Luyuan Zhang1,2,3, Ms. Miao Fang1, Mr. Tong Zhang1,4, Ms. Huan Jiang1,4, Dr. Mengting Zhang1,4, Dr. Xiaolin Hou1,2,3
1State Key Laboratory of Loess and Quaternary Geology, Shaanxi Key Laboratory of Accelerator Mass Spectrometry Technology and Application, Xi’an AMS Center, Institute Of Earth Environment, Chinese Academy Of Sciences, Xi’an, China, 2Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, Xi’an, China, 3Open Studio for Oceanic-Continental Climate and Environment Changes, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, China, 4Xi’an Institute for Innovative Earth Environment Research, Xi’an, China
¹²⁹I in soil and sediments are paid increasing attention for the purpose of environmental radioactivity monitoring, and understanding the historic nuclear activities and their impacts. Accurate measurement of ¹²⁹I is vital, which greatly increases the requirement of various certified reference materials (CRMs). However, only few CRMs with low level of ¹²⁹I are available for accurate determination of ¹²⁹I in samples remote from nuclear sites and facilities. Here, this work investigated the concentrations of ¹²⁹I and ¹²⁷I, and ¹²⁹I/¹²⁷I atomic ratios in twenty Chinese soil and sediment CRMs commercially available, as well as one in-house soil standard material (XASTD), with high-temperature pyrolysis combustion in coupling with ICP-MS and accelerator mass spectrometry (AMS) measurements. This study presents that ¹²⁹I concentrations in the twenty CRMs and one laboratory soil standard range from 0.31×10⁶ atoms/g to 34.7×10⁶ atoms/g, which were 1-4 orders of magnitude lower than those reference materials in use. For accurate measurement of ¹²⁹I, the effect of salinity content in the samples on iodine current intensity of AMS measurement is firstly discussed. Significant salinity effect could occur when high-salinity sample is analysed, which is mainly due to the formation of abundant strong oxidant during the pyrolysis process, resulting in iodine existing as iodate instead of iodide. And finally, an analytical procedure was recommended for the low- and high-salinity soil and sediment samples. In summary, these reported data of the CRMs and the laboratory in-house control soil standard material would broaden the group of available reference materials, be useful for method development of low-level ¹²⁹I samples, interlaboratory comparison and short- and long-term quality control, as well as extend ¹²⁹I applications in geological, environmental and nuclear sciences. .
Dr. Luyuan Zhang got her PhD degree in Radiochemistry from Technical University of Denmark, and work in the Institute of Earth Environment, Chinese Academy of Sciences. Her research is focusing on methodology, process tracing and nuclear safety applications of long-lived radionuclides using accelerator mass spectrometer and other MS systems, such as iodine-129, plutonium, technetium-99, ect. Recently, she is also involved in Anthropocene study using anthropogenic radionuclides as novel proxies.