Published Online: 15 JUN 2010
Copyright © 2006 John Wiley & Sons, Ltd
Encyclopedia of Inorganic Chemistry
How to Cite
Shaw, G. and Ashworth, D. 2010. Selenium: Radionuclides. Encyclopedia of Inorganic Chemistry. .
- Published Online: 15 JUN 2010
Selenium in the environment has been studied intensively for several decades, since it is both a trace nutrient and a toxin. It is a ubiquitous element in soils, waters, and the atmosphere, with chemical similarities to the other group 16 elements sulfur, polonium, and tellurium. Important selenium species in environmental media include inorganic oxyanions as well as organic species produced by biological methylation mechanisms. The only probable long-term source of radioactive selenium to the environment is the leakage from radioactive waste repositories. Only 79Se is of concern in this respect, since it is the only long-lived radioactive isotope of selenium (physical half-life = 377 000 years). Under alkaline geochemical conditions, there is the potential for 79Se to migrate from geological radioactive waste repositories in very small quantities over very long periods. It is expected that any 79Se released into the environment will behave in the same way as nonradioactive selenium, though the kinetics of isotopic exchange between 79Se and stable selenium in soils, sediments, and other environmental media have never been studied over timescales relevant to radioactive waste disposal. It is unlikely that environmental concentrations of 79Se will ever lead to exposures approaching the intake levels associated with stable selenium. Any exposure that does occur is likely to be primarily through the dietary intake pathway, since the principal environmental reservoirs, and therefore potential sources, of selenium in the environment are waters and soils.
- elemental selenium;
- human exposure