129I is used as a tracer substance to help determine the impact of nuclear reactions on neighboring surroundings. 129I is biophilic and therefore is often concentrated in plants or soils with a high organic content.
129I can be used in the identification of very old waters by correlating the amount of natural 129I or its 129Xe decay product. It can also be used in the identification of younger bodies of water due to the increased anthropogenic 129I levels due to nuclear reaction fallout. The following is a list of applications of 129I analysis:
- estimation of groundwater residence time
- tracing of brine migration
- identification of hydrocarbon source rocks
- tracing the movement of radioactive contaminant plumes
129I is a naturally occurring radioactive isotope of iodine with a half-life of 15.7 million years. Although it occurs naturally in the environment, 129I is formed more abundantly during the fission of uranium and/or plutonium in nuclear energy reactors and the detonation of nuclear weapons. Iodine itself is a non-metallic element, a purplish-black crystalline solid with the rare physical property of sublimation in which the substance can go directly from a solid state to a gaseous state.
129I extraction from aqueous samples follows modified procedure of the one outlined by J. Kleinberg and G. Cowan, The Radiochemistry of Fluorine, Chlorine, Bromine, Iodine, Los Alamos National Laboratory where the final product precipitated as AgI is pressed into a target and analyze on the HVE 3MV Tandetron.