Geochemical controls of iodine uptake and transport in Savannah River Site subsurface sediments

Emerson, Hilary P.; Xu, Chen; Ho, Yi‐Fang; Zhang, S.; Schwehr, Kathleen A.; Lilley, Michael; Kaplan, Daniel I.; Santschi, Peter H.; Powell, Brian A.

doi:10.1016/j.apgeochem.2014.03.002

Cited by 34 publications

(34 citation statements)

References 20 publications

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“…Several studies of sorption in shallow soils indicate that the OM is a primary control on iodine sorption (Assemi and Erten 1994, Bird and Schwartz 1997, Emerson et al 2014, Fukui et al 1996, Kaplan 2003, Neal and Truesdale 1976, Sheppard and Thibault 1991, Whitehead 1974, Yoshida et al 1992, Yu et al 1996. In a survey of 26 soils and sediments samples from across the United States, with natural OM concentrations ranging from 0.046 to 0.5 wt % (except for one peat sample that was 28.1 wt%), Hu et al (2009) reported that ~90% of the total iodine in soils was present as organic iodine, while inorganic iodine species became important only in sediments with low OM contents.…”

Section: A22 Influence Of Sediment Organic Matter On Iodine Sorptionmentioning

confidence: 99%

“…It is not clear from these studies whether the changes in redox alter the iodine speciation or the OM speciation, or both. Emerson et al (2014) conducted identical sorption experiments under oxidizing (lab bench) and reducing (inside an inert atmosphere glovebox) environments using SRS sediments. They measured significantly lower K d values when either iodide or iodate was added to the soil suspension under reducing conditions.…”

Section: A22 Influence Of Sediment Organic Matter On Iodine Sorptionmentioning

confidence: 99%

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Conceptual Model of Iodine Behavior in the Subsurface at the Hanford Site

Truex

Lee

Johnson

et al. 2015

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DOC Dissolved organic carbon DOE U.S. Department of Energy DPMAS Direct-polarization magic-angle spinning DWS Drinking water standard EXAFS Extended X-ray absorption fine structure spectra Eh Oxidation/reduction potential Stored in single-shell and double-shell tanks Discharged to liquid disposal sites (e.g., cribs and trenches) Released to the atmosphere during fuel reprocessing operations Captured by off-gas absorbent devices (silver reactors) at chemical separations facilities (PUREX, B-Plant, T-Plant, and REDOX)

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Section: A22 Influence Of Sediment Organic Matter On Iodine Sorptionmentioning

confidence: 99%

Section: A22 Influence Of Sediment Organic Matter On Iodine Sorptionmentioning

confidence: 99%

Conceptual Model of Iodine Behavior in the Subsurface at the Hanford Site

Truex

Lee

Johnson

et al. 2015

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“…Following the 2011 Fukushima nuclear reactor catastrophe, westerly winds deposited a large portion of the radioactive iodine in the Pacific Ocean, where radioactive IO 3 Ϫ and I Ϫ were the predominant 129 I forms (11)(12)(13). Radioactive iodine is also found in contaminated groundwater at the U.S. Department of Energy Savannah River and Hanford sites (9,13,14). Despite the human health concerns surrounding the fate and transport of radioactive iodine in the environment, the molecular mechanism of microbial IO 3 Ϫ reduction remains poorly understood (15).…”

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confidence: 99%

Metal Reduction and Protein Secretion Genes Required for Iodate Reduction by Shewanella oneidensis

Toporek

Mok

Shin

et al. 2019

Appl Environ Microbiol

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The metal-reducing gammaproteobacterium Shewanella oneidensis reduces iodate (IO 3 Ϫ ) as an anaerobic terminal electron acceptor. Microbial IO 3 Ϫ electron transport pathways are postulated to terminate with nitrate (NO 3 Ϫ ) reductase, which reduces IO 3 Ϫ as an alternative electron acceptor. Recent studies with S. oneidensis, however, have demonstrated that NO 3Ϫ reductase is not involved in IO 3 Ϫ reduction. The main objective of the present study was to determine the metal reduction and protein secretion genes required for IO 3 Ϫ reduction by Shewanella oneidensis with lactate, formate, or H 2 as the electron donor. With all electron donors, the type I and type V protein secretion mutants retained wild-type IO 3Ϫ reduction activity, while the type II protein secretion mutant lacking the outer membrane secretin GspD was impaired in IO 3 Ϫ reduction. Deletion mutants lacking the cyclic AMP receptor protein (CRP), cytochrome maturation permease CcmB, and inner membrane-tethered c-type cytochrome CymA were impaired in IO 3Ϫ reduction with all electron donors, while deletion mutants lacking c-type cytochrome MtrA and outer membrane ␤-barrel protein MtrB of the outer membrane MtrAB module were impaired in IO 3Ϫ reduction with only lactate as an electron donor. With all electron donors, mutants lacking the c-type cytochromes OmcA and MtrC of the metalreducing extracellular electron conduit MtrCAB retained wild-type IO 3 Ϫ reduction activity. These findings indicate that IO 3 Ϫ reduction by S. oneidensis involves electron donor-dependent metal reduction and protein secretion pathway components, including the outer membrane MtrAB module and type II protein secretion of an unidentified IO 3 Ϫ reductase to the S. oneidensis outer membrane.IMPORTANCE Microbial iodate (IO 3 Ϫ ) reduction is a major component in the biogeochemical cycling of iodine and the bioremediation of iodine-contaminated environments; however, the molecular mechanism of microbial IO 3 Ϫ reduction is poorly understood. Results of the present study indicate that outer membrane (type II) protein secretion and metal reduction genes encoding the outer membrane MtrAB module of the extracellular electron conduit MtrCAB are required for IO 3 Ϫ reduction by S. oneidensis. On the other hand, the metal-reducing c-type cytochrome MtrC of the extracellular electron conduit is not required for IO 3 Ϫ reduction by S. oneidensis. These findings indicate that the IO 3 Ϫ electron transport pathway terminates with an as yet unidentified IO 3Ϫ reductase that associates with the outer membrane MtrAB module to deliver electrons extracellularly to IO 3 Ϫ .

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“…In summary, our understanding of 129 I geochemistry has greatly improved, reducing the uncertainty associated with the PA's conceptual model, thereby permitting us to reduce the conservatism presently incorporated in PA input values to describe 129 I fate and transport in the SRS subsurface environment. ............................................................................................................................................ 32 Appendix A: Additional Iodine K d Values for Wetland Sediments (Emerson et al 2012) ....................... 35 SRNL-STI-2012 Revision 0 vi Table 3. Characterization of sediment used by Xu et al (2011).............................................................. 10 Table 4.…”

Section: Prepared For Us Department Of Energymentioning

confidence: 99%

“…The objective of this report is to critically review recent field and laboratory 129 I geochemical research and evaluate their implications on SRS performance assessments. The implications of three recent studies using SRS groundwater and sediment will be reviewed (Emerson and Powell, 2012;Lilley et al, 2010;Otosaka et al, 2011;Xu et al, 2011a). The scope of this report was limited to whether the relatively low concentrations of organic carbon in the SRS subsurface sediment (200 to 600 ppm C) influence 129 I geochemistry.…”

Section: Improved Analytical Capabilities Leading To New Understandinmentioning

confidence: 99%

Radioiodine Geochemistry in the SRS Subsurface Environment

Kaplan¹,

Emerson²,

Powell³

et al. 2013

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Iodine-129 is one of the key risk drivers for several Savannah River Site (SRS) performance assessments (PA), including that for the Low-Level Waste Disposal Facility in E-Area. In an effort to reduce the uncertainty associated with the conceptual model and the input values used in PA, several studies have recently been conducted dealing with radioiodine geochemistry at the SRS. The objective of this report was to review these recent studies and evaluate their implications on SRS PA calculations. For the first time, these studies measured iodine speciation in SRS groundwater and provided technical justification for assuming the presence of more strongly sorbing species (iodate and organo-iodine), and measured greater iodine sediment sorption when experiments included these newly identified species; specifically they measured greater sorption coefficients (K d values: the concentration ratio of iodine on the solid phase divided by the concentration in the aqueous phase). Based on these recent studies, new best estimates were proposed for future PA calculations. The new K d values are greater than previous recommended values. Present and proposed best-estimate sediment iodine K d values for SRS PA calculations. Subsurface sediment Present K d (mL/g) Proposed new K d values (mL/g

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Geochemical controls of iodine uptake and transport in Savannah River Site subsurface sediments

Cited by 34 publications

References 20 publications

Conceptual Model of Iodine Behavior in the Subsurface at the Hanford Site

Conceptual Model of Iodine Behavior in the Subsurface at the Hanford Site

Metal Reduction and Protein Secretion Genes Required for Iodate Reduction by Shewanella oneidensis

Radioiodine Geochemistry in the SRS Subsurface Environment

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