1
|
Kaplan DI, Nichols R, Xu C, Lin P, Yeager C, Santschi PH. Large seasonal fluctuations of groundwater radioiodine speciation and concentrations in a riparian wetland in South Carolina. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 816:151548. [PMID: 34780820 DOI: 10.1016/j.scitotenv.2021.151548] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Revised: 10/15/2021] [Accepted: 11/05/2021] [Indexed: 06/13/2023]
Abstract
Recent studies evaluating multiple years of groundwater radioiodine (129I) concentration in a riparian wetland located in South Carolina, USA identified strong seasonal concentration fluctuations, such that summer concentrations were much greater than winter concentrations. These fluctuations were observed only in the wetlands but not in the upland portion of the plume and only with 129I, and not with other contaminants of anthropogenic origin: nitrate/nitrite, strontium-90, technecium-99, tritium, or uranium. This unexplained observation was hypothesized to be the result of strongly coupled processes involving hydrology, water temperature, microbiology, and chemistry. To test this hypothesis, an extensive historical groundwater database was evaluated, and additional measurements of total iodine and iodine speciation were made from recently collected samples. During the summer, the water table decreased by as much as 0.7 m, surface water temperature increased by as much as 15 °C, and total iodine concentrations were consistently greater (up to 680%) than the following winter months. Most of the additional iodine observed in the summer could be attributed to proportional gains in organo-iodine, and not iodide or iodate. Furthermore, 129I concentrations were observed to be two-orders-of-magnitude greater at the bottom of the upland aquifer than at the top. A coupled hydrological and biogeochemical conceptual model is proposed to tie these observations together. First, as the surface water temperature increased during the summer, microbial activity was enhanced, which in turn stimulated the formation of mobile organo-I. Hydrological processes were also likely involved in the observed iodine seasonal changes: (1) as the water table decreased in summer, the remaining upland water entering the wetland was comprised of a greater proportion of water containing elevated iodine concentrations from the low depths, and (2) water flow paths in summer changed such that the wells intercepted more of the contaminant plume and less of the diluting rainwater (due to evapotranspiration) and streamwater (as the lower levels promote a predominantly recharging system). These results underscore the importance of coupled processes influencing contaminant concentrations, and the need to assess seasonal contaminant variations to optimize long-term monitoring programs of wetlands.
Collapse
Affiliation(s)
- Daniel I Kaplan
- Savannah River National Laboratory, Aiken, SC 29808, United States.
| | - Ralph Nichols
- Savannah River National Laboratory, Aiken, SC 29808, United States
| | - Chen Xu
- Department of Marine Sciences, Texas A&M University, Galveston, TX 77551, United States
| | - Peng Lin
- Department of Marine Sciences, Texas A&M University, Galveston, TX 77551, United States
| | - Chris Yeager
- Los Alamos National Laboratory, Los Alamos, NM 87545, United States
| | - Peter H Santschi
- Department of Marine Sciences, Texas A&M University, Galveston, TX 77551, United States
| |
Collapse
|
2
|
Qian K, Li J, Chi Z, Liu W, Wang Y, Xie X. Natural organic matter-enhanced transportation of iodine in groundwater in the Datong Basin: Impact of irrigation activities. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 730:138460. [PMID: 32388361 DOI: 10.1016/j.scitotenv.2020.138460] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 03/30/2020] [Accepted: 04/03/2020] [Indexed: 06/11/2023]
Abstract
Local residents in the Datong Basin of northern China are exposed to groundwater with elevated iodine concentrations. Natural organic matter (NOM) has been linked to the heterogeneous distribution of elevated iodine in groundwater used for irrigation purposes, but little is known about the effects of hydrologic fluctuations and NOM characteristics on the transport and enrichment of iodine in the groundwater. Cl/Br molar ratios in Datong Basin groundwater range widely from 133 to 2099. A rapid increase in Cl/Br molar ratio with increasing Cl content indicates hydrologic fluctuations from the upper groundwater to the deeper aquifer due to large-scale irrigation activities in the Basin. A two end-member model of groundwater δ2H and δ18O values suggests the contribution of upper water recharging groundwater ranges from 20.7 to 49.5%. This vertical recharge process predominantly controls iodine enrichment and distribution in the groundwater. Additionally, the correlation between DOC concentration and δ18O signatures indicates considerable fresh organic matter is imported into the aquifer during the vertical recharge process. Iodine mobilization is likely promoted by young carbon transported to the deeper aquifer in the organo‑iodine form. Excitation-emission matrix (EEM) results indicate humic-like substances dominate NOM in the groundwater. Evidence from a PARAFAC model suggests organic matter in groundwater samples is associated with microbially-mediated degradation processes in an anaerobic environment. The drawdown migration of organic matter from the upper soil/sediments or surface could provide an extra energy source that promotes microbial activity. Buried sedimentary iodine coupled with anaerobic microbial respiration of subsurface organic carbon within the aquifer could lead to the release of iodine into the groundwater. These findings pave the way for a more comprehensive assessment of the susceptibility of drinking water aquifers, thereby supporting the management of groundwater resources.
Collapse
Affiliation(s)
- Kun Qian
- State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China
| | - Junxia Li
- State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China
| | - Zeyong Chi
- State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China
| | - Wenjing Liu
- State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China
| | - Yanxin Wang
- State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China
| | - Xianjun Xie
- State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China.
| |
Collapse
|
3
|
Cordova EA, Garayburu-Caruso V, Pearce CI, Cantrell KJ, Morad JW, Gillispie EC, Riley BJ, Colon FC, Levitskaia TG, Saslow SA, Qafoku O, Resch CT, Rigali MJ, Szecsody JE, Heald SM, Balasubramanian M, Meyers P, Freedman VL. Hybrid Sorbents for 129I Capture from Contaminated Groundwater. ACS APPLIED MATERIALS & INTERFACES 2020; 12:26113-26126. [PMID: 32421326 DOI: 10.1021/acsami.0c01527] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Radioiodine (129I) poses a risk to the environment due to its long half-life, toxicity, and mobility. It is found at the U.S. Department of Energy Hanford Site due to legacy releases of nuclear wastes to the subsurface where 129I is predominantly present as iodate (IO3-). To date, a cost-effective and scalable cleanup technology for 129I has not been identified, with hydraulic containment implemented as the remedial approach. Here, novel high-performing sorbents for 129I remediation with the capacity to reduce 129I concentrations to or below the US Environmental Protection Agency (EPA) drinking water standard and procedures to deploy them in an ex-situ pump and treat (P&T) system are introduced. This includes implementation of hybridized polyacrylonitrile (PAN) beads for ex-situ remediation of IO3--contaminated groundwater for the first time. Iron (Fe) oxyhydroxide and bismuth (Bi) oxyhydroxide sorbents were deployed on silica substrates or encapsulated in porous PAN beads. In addition, Fe-, cerium (Ce)-, and Bi-oxyhydroxides were encapsulated with anion-exchange resins. The PAN-bismuth oxyhydroxide and PAN-ferrihydrite composites along with Fe- and Ce-based hybrid anion-exchange resins performed well in batch sorption experiments with distribution coefficients for IO3- of >1000 mL/g and rapid removal kinetics. Of the tested materials, the Ce-based hybrid anion-exchange resin was the most efficient for removal of IO3- from Hanford groundwater in a column system, with 50% breakthrough occurring at 324 pore volumes. The functional amine groups on the parent resin and amount of active sorbent in the resin can be customized to improve the iodine loading capacity. These results highlight the potential for IO3- remediation by hybrid sorbents and represent a benchmark for the implementation of commercially available materials to meet EPA standards for cleanup of 129I in a large-scale P&T system.
Collapse
Affiliation(s)
- Elsa A Cordova
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Vanessa Garayburu-Caruso
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Carolyn I Pearce
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Kirk J Cantrell
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Joseph W Morad
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Elizabeth C Gillispie
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Brian J Riley
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Ferdinan Cintron Colon
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Tatiana G Levitskaia
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Sarah A Saslow
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Odeta Qafoku
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Charles T Resch
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Mark J Rigali
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Jim E Szecsody
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Steve M Heald
- Advanced Photon Source, Argonne National Laboratory, Argonne Illinois 60439, United States
| | | | - Peter Meyers
- Resin Tech, West Berlin, New Jersey 08091, United States
| | - Vicky L Freedman
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| |
Collapse
|
4
|
Neeway JJ, Kaplan DI, Bagwell CE, Rockhold ML, Szecsody JE, Truex MJ, Qafoku NP. A review of the behavior of radioiodine in the subsurface at two DOE sites. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 691:466-475. [PMID: 31323591 DOI: 10.1016/j.scitotenv.2019.07.146] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 07/10/2019] [Accepted: 07/10/2019] [Indexed: 06/10/2023]
Abstract
Multiple processes affect the fate of the radioactive isotope 129I in the environment. Primary categories of these processes include electron transfer reactions mediated by minerals and microbes, adsorption to sediments, interactions with organic matter, co-precipitation, and volatilization. A description of dominant biogeochemical processes is provided to describe the interrelationship of these processes and the associated iodine chemical species. The majority of the subsurface iodine fate and transport studies in the United States have been conducted at U.S. Department of Energy (DOE) sites where radioisotopes of iodine are present in the environment and stored waste. The DOE Hanford Site and Savannah River Site (SRS) are used to illustrate how the iodine species and dominant processes at a site are controlled by the prevailing site biogeochemical conditions. These sites differ in terms of climate (arid vs. sub-tropical), major geochemical parameters (e.g., pH ~7.5 vs. 4), and mineralogy (carbonate vs. Fe/Al oxide dominated). The iodine speciation and dominant processes at a site also have implications for selection and implementation of suitable remedy approaches for 129I.
Collapse
Affiliation(s)
- James J Neeway
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Daniel I Kaplan
- Savannah River National Laboratory, Aiken, SC, United States of America
| | | | - Mark L Rockhold
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - James E Szecsody
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Michael J Truex
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Nikolla P Qafoku
- Pacific Northwest National Laboratory, Richland, WA, United States of America.
| |
Collapse
|
5
|
García-León M. Accelerator Mass Spectrometry (AMS) in Radioecology. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2018; 186:116-123. [PMID: 28882579 DOI: 10.1016/j.jenvrad.2017.06.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Accepted: 06/20/2017] [Indexed: 06/07/2023]
Abstract
Accelerator Mass Spectrometry (AMS) provides with an excellent sensitivity for the determination of radionuclides in the environment. In fact, conventional radiometric techniques can hardly compete with AMS in the solution of many problems involving the measurement of very low levels of radioactivity in Nature. For that reason, during the last years AMS has become a powerful tool for Radioecology studies. In this paper a review is done on the evolution of AMS applications to the measurement of environmental radioactivity and, therefore, its contribution to the understanding of radionuclide behavior in Nature. For that, the advantages of using AMS to determine key nuclides as 129I, 14C, Pu-isotopes and others in different natural compartments will be discussed. The content of the paper is illustrated with the contributions to these studies of the Spanish National Center for Accelerators (CNA) AMS systems.
Collapse
Affiliation(s)
- M García-León
- Universidad de Sevilla, Centro Nacional de Aceleradores, Avda. T. A. Edison, 7, 41092 Sevilla, Spain.
| |
Collapse
|
6
|
Santschi PH, Xu C, Zhang S, Schwehr KA, Lin P, Yeager CM, Kaplan DI. Recent advances in the detection of specific natural organic compounds as carriers for radionuclides in soil and water environments, with examples of radioiodine and plutonium. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2017; 171:226-233. [PMID: 28286302 DOI: 10.1016/j.jenvrad.2017.02.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 02/25/2017] [Accepted: 02/26/2017] [Indexed: 06/06/2023]
Abstract
Among the key environmental factors influencing the fate and transport of radionuclides in the environment is natural organic matter (NOM). While this has been known for decades, there still remains great uncertainty in predicting NOM-radionuclide interactions because of lack of understanding of radionuclide interactions with the specific organic moieties within NOM. Furthermore, radionuclide-NOM studies conducted using modelled organic compounds or elevated radionuclide concentrations provide compromised information related to true environmental conditions. Thus, sensitive techniques are required not only for the detection of radionuclides, and their different species, at ambient and/or far-field concentrations, but also for potential trace organic compounds that are chemically binding these radionuclides. GC-MS and AMS techniques developed in our lab are reviewed here that aim to assess how two radionuclides, iodine and plutonium, form strong bonds with NOM by entirely different mechanisms; iodine tends to bind to aromatic functionalities, whereas plutonium binds to N-containing hydroxamate siderophores at ambient concentrations. While low-level measurements are a prerequisite for assessing iodine and plutonium migration at nuclear waste sites and as environmental tracers, it is necessary to determine their in-situ speciation, which ultimately controls their mobility and transport in natural environments. More importantly, advanced molecular-level instrumentation (e.g., nuclear magnetic resonance (NMR) and Fourier-transform ion cyclotron resonance coupled with electrospray ionization (ESI-FTICRMS) were applied to resolve either directly or indirectly the molecular environments in which the radionuclides are associated with the NOM.
Collapse
Affiliation(s)
| | - C Xu
- Texas A&M-Galveston, Galveston, TX, USA
| | - S Zhang
- Texas A&M-Galveston, Galveston, TX, USA
| | | | - P Lin
- Texas A&M-Galveston, Galveston, TX, USA
| | - C M Yeager
- Los Alamos National Laboratory, Los Alamos, NM, USA
| | - D I Kaplan
- Savannah River National Laboratory, Aiken, SC, USA
| |
Collapse
|
7
|
Yeager CM, Amachi S, Grandbois R, Kaplan DI, Xu C, Schwehr KA, Santschi PH. Microbial Transformation of Iodine: From Radioisotopes to Iodine Deficiency. ADVANCES IN APPLIED MICROBIOLOGY 2017; 101:83-136. [PMID: 29050668 DOI: 10.1016/bs.aambs.2017.07.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Iodine is a biophilic element that is important for human health, both as an essential component of several thyroid hormones and, on the other hand, as a potential carcinogen in the form of radioiodine generated by anthropogenic nuclear activity. Iodine exists in multiple oxidation states (-1, 0, +1, +3, +5, and +7), primarily as molecular iodine (I2), iodide (I-), iodate [Formula: see text] , or organic iodine (org-I). The mobility of iodine in the environment is dependent on its speciation and a series of redox, complexation, sorption, precipitation, and microbial reactions. Over the last 15years, there have been significant advances in iodine biogeochemistry, largely spurred by renewed interest in the fate of radioiodine in the environment. We review the biogeochemistry of iodine, with particular emphasis on the microbial processes responsible for volatilization, accumulation, oxidation, and reduction of iodine, as well as the exciting technological potential of these fascinating microorganisms and enzymes.
Collapse
|