title: Temporal variation of iodine concentration and speciation (127I and 129I) in wetland groundwater from the Savannah River Site, USA.
abstract: (129)I 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 (127)I and (129)I showed significant temporal variations, ranging from 68-196 nM for (127)I and <5-133 pCi/L for (129)I. These iodine isotopes were significantly correlated with groundwater acidity and nitrate, two parameters elevated within the contaminant plume. Additionally, (129)I levels were significantly correlated with those of (127)I, suggesting that biogeochemical controls on (127)I and (129)I 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 system where few single ancillary parameters changed in a systematic manner with iodine speciation. Instead, changes in groundwater chemistry and microbial activity, driven by surface hydrological events, interact to control iodine speciation and mobility. Future radiological risk models should consider the flux of (129)I in response to temporal changes in wetland hydrologic and chemical conditions.
authors.affiliation: Laboratory for Oceanographic and Environmental Research, Department of Marine Sciences, Texas A&M University , Building 3029, 200 Seawolf Parkway, Galveston, Texas 77554, United States.
authors.forename: Saijin
authors.initials: S
authors.lastname: Zhang
authors.forename: Yi-Fang
authors.initials: YF
authors.lastname: Ho
authors.forename: Danielle
authors.initials: D
authors.lastname: Creeley
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Roberts
authors.forename: Chen
authors.initials: C
authors.lastname: Xu
authors.forename: Hsiu-Ping
authors.initials: HP
authors.lastname: Li
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Schwehr
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Kaplan
authors.forename: Chris M
authors.initials: CM
authors.lastname: Yeager
authors.forename: Peter H
authors.initials: PH
authors.lastname: Santschi
mesh_terms: D060587:Groundwater / Q000032:analysis* / Q000737:chemistry; D062070:Hydrology / Q000379:methods; D007455:Iodine / Q000032:analysis*; D007456:Iodine Isotopes / Q000032:analysis; D007457:Iodine Radioisotopes / Q000032:analysis*; D008962:Models, Theoretical; D012307:Risk Factors; D045483:Rivers / Q000737:chemistry*; D013022:South Carolina; D014875:Water Pollutants, Radioactive / Q000032:analysis*; D053833:Wetlands
chemical_list: D007456:Iodine Isotopes; D007457:Iodine Radioisotopes; D014875:Water Pollutants, Radioactive; D007455:Iodine