Atmospheric Dispersal of 129Iodine from Nuclear Fuel Reprocessing Facilities

129I/127I ratios measured in meteoric water and epiphytes from the continental United States are higher than those measured in coastal seawater or surface freshwater and suggest long-range atmospheric transport of 129I from the main source for the earth's surface inventory, viz., nuclear fuel reprocessing facilities. The median ratio for 14 meteoric water samples is 2100 × 10-12, corresponding to a 129I concentration of 2.5 × 107 atoms/L, whereas 9 epiphyte samples have a median ratio of 1800 × 10-12. Calculated deposition rates of 129I in the continental United States reveal that a small but significant fraction of the atmospheric releases from the nuclear fuel reprocessing facilities at Sellafield, England, and Cap de La Hague, France, is deposited after distribution by long-range transport. The inferred dominant mode of transport is easterly, within the troposphere, mainly in the form of the organic gas methyl iodide.