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

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• 作者：Saijin Zhang ; Yi-Fang Ho ; Danielle Creeley ; Kimberly A. Roberts ; Chen Xu ; Hsiu-Ping Li ; Kathleen A. Schwehr ; Daniel I. Kaplan ; Chris M. Yeager ; Peter H. Santschi
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：October 7, 2014
• 年：2014
• 卷：48
• 期：19
• 页码：11218-11226
• 全文大小：413K
• ISSN：1520-5851

文摘

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鈥?012) from a single location. Total ¹²⁷I and ¹²⁹I showed significant temporal variations, ranging from 68鈥?96 nM for ¹²⁷I and <5鈥?33 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 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 ¹²⁹I in response to temporal changes in wetland hydrologic and chemical conditions.