Analysis of 129I and its Application as Environmental Tracer

Iodine-129 occurs naturally, but dominates in the environment by human nuclear activity in the past 60 years. Due to active chemical and environmental properties of iodine and enhanced analytical capacity for 129I measurement, application of 129I as an environmental tracer has highly increased in the past 10 years. Neutron activation analysis and accelerator mass spectrometry are the only techniques for measurement of 129I in environmental level. This article mainly compares these two analytical techniques for the determination of 129I in environmental level, and highlights the new progresses of analytical methods for its chemical separation and sensitive measurement. The naturally occurring 129I has been used for age dating of samples/events in a range of 2-80 Ma. For this purpose an initial value of 129I has to be measured. Some new progresses on the establishment of initial 129I level in terrestrial system are presented. A large amount of anthropogenic 129I has been released to the environment mainly by reprocessing of nuclear fuel. Anthropogenic 129I provides a good oceanographic tracer for studying the circulation and exchange of water mass. The speciation analysis of 129I can also be used for investigation of geochemical cycle of stable iodine. Some representive research works on the environmental tracer application of 129I are summarized.