[en] ¹²⁹I has been analyzed in both aqueous and soil samples to characterize the environmental impact of the Savannah River Plant (SRP) reprocessing operations. ¹²⁹I was quantified by a neutron activation procedure with γ-ray spectrometric detection [Ge(Li)]. For many samples, natural iodine (¹²⁷I) was also quantified. A wide range of samples can be accommodated by a combustion-based preirradiation isolation technique. ¹²⁹I amounts as low as 3.8 fCi can be determined with counting times of less than 30 minutes (s/sub rel/ = 10%). Deposition of ¹²⁹I in the environment via aqueous and airborne emissions has been studied. Data from analysis of seepage basin contents, spring water, on-plant streams, and the Savannah River show that ¹²⁹I from the seepage basins migrates easily through the soil with the groundwater, eventually reaching the Savannah River. Annual aqueous release rates were estimated to be 16 to 27 mCi/year. Data from analysis of soils from distances up to 159 km from SRP show above background levels of ¹²⁹I in both the minimum and maximum airborne transport directions. The soil results are compared with a wind dispersion model. The vertical distribution of ¹²⁹I in the soil was determined to a depth of 61 cm