Temporal Variation of Iodine Concentration and Speciation (127I and 129I) in Wetland Groundwater from the Savannah River Site, USA

129I derived from a former radionuclide disposal basin located on the Savannah River Site (SRS) has concentrated in a wetland 600 m downstream. To evaluate temporal environmental influences on iodine speciation and mobility in this subtropical wetland environment, groundwater was collected over a three-year period (2010–2012) from a single location. Total 127I and 129I showed significant temporal variations, ranging from 68–196 nM for 127I and <5–133 pCi/L for 129I. These iodine isotopes were significantly correlated with groundwater acidity and nitrate, two parameters elevated within the contaminant plume. Additionally, 129I levels were significantly correlated with those of 127I, suggesting that biogeochemical controls on 127I and 129I are similar within the SRS aquifer/wetland system. Iodine speciation demonstrates temporal variations as well, reflecting effects from surface recharges followed by acidification of groundwater and subsequent formation of anaerobic conditions. Our results reveal a complex...