[21a-E303-1~12] 2.4 Accelerator Mass Spectrometry, Accelerator Beam Analysis

[21a-E303-5] Study on iodine isotope system on the earth environment

〇Hiroyuki Matsuzaki¹ (1.MALT, Univ. of Tokyo)

Keywords:iodine-129, iodine isotope system, iodine dynamics

Before 1950’s, the sources of iodine-129 (half-life = 15.7 myr) are limited to those of natural processes, i.e., the interaction of cosmic ray and the spontaneous fission of uranium. The production rate should not have been changed drastically for long time, and geochemical circulation time of iodine is generally shorter than its half-life, people has been considering there has been an equilibrium isotopic ratio (¹²⁹I/¹²⁷I) in a steady state. However, based on a simple iodine dynamics model, a steady state with incomplete iodine mixing between ocean and sediments resulting in different isotopic ratio (i.e., marine: 2.0E-13; crust: 1.5E-12) is possible with certain parameters of iodine dynamics.