Glen Snyder

Nuclear reprocessing of spent fuel rods, coupled with nuclear bomb tests of the 1960's, has greatly increased global concentrations of several man-made isotopes. The release of these isotopes into the environment allows us to determine the extent to which modern waters have migrated into aquifers, and they also provide an indicator of how different elements migrate through ecosystems. Several of these isotopes, such as ¹³¹I or ³H, have short half-lives and generally return to pre-anthropogenic levels after months or several decades. In the case of long-lived ³⁶Cl, dilution from "dead" chloride in seawater, has also caused ³⁶Cl/Cl ratios to return to near-preanthropogenic values. My research has focused on global variations in ¹²⁹I in rivers and lakes, and the effect of different climate-related factors on iodine mobilization. These factors are important to human health, given that inhabitants of certain regions are more prone to iodine deficiency syndrome. In the case of nuclear accidents, the mobility of iodine through the food chain is also important, since the dispersal of short-lived iodine isotopes from fission products is a contributing factor to thyroid cancer. Prior to human nuclear activities, the total pre-anthropogenic reservoir of ¹²⁹iodine in the oceans was only 90 kg. Today, major point-source releases of ¹²⁹I into the oceans come from two major reprocessing plants in Europe, Sellafield and La Hague.