- 第3日 5月17日（木） 16:55～17:15 C会場（星雲2）
Long-lived radionuclides that have an abundance ratio of 10–12 to 10–15 to their stable isotopes in the earth’s surface are referred here as femto-level isotopes. Many of those nuclides (such as 10Be, 14C, 26Al, 36Cl, and 129I) have been effectively measured by Accelerator Mass Spectrometry (AMS). Because the variations of the nuclides result from the natural production (mainly due to cosmic rays), transportation and circulation, and anthropogenic nuclear processes, the analysis on the femto-level isotopes in natural archives is useful to evaluate the natural and anthropogenic influences on the earth’s system in the past and present.
Polar ice cores are the best archives preserving the femto-level isotopes from the atmosphere. For example, 10Be in Greenland and Antarctic ice cores has been frequently used to elucidate the cosmic-ray history associated with solar and geomagnetic modulations (e.g. Horiuchi et al., 2008, 2016, and references therein). Likewise, 36Cl has been analyzed to investigate the both anthropogenic nuclear testing and cosmic rays. Very recently, 129I in a Greenland ice core was applied to elucidate the history of the both nuclear bomb testing and fuel reprocessing (Bautista et al., 2018). In this presentation, I will present some of the recent progresses in ice-core studies of the femto-level isotopes.