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oai:www.ideals.illinois.edu:2142/102885 2023-07-11 col_2142_5131 col_2142_16322 com_2142_5130 com_2142_16321 com_2142_13459 com_2142_8903

Johnson, Thomas M. Johnson, Thomas M. Druhan, Jennifer L Lundstrom, Craig C. Sanford, Robert A. Jemison, Noah 2019-02-08T18:39:38Z 2019-02-08T18:39:38Z 2021-02-09T10:15:38Z 2018-08-27 2018-12 Tracking U immobilization through U(VI) reduction and mobilization induced by U(IV) oxidation using U concentrations alone is challenging, as groundwater transport, aquifer heterogeneity, and U(VI) adsorption can complicate data interpretation. U isotopes (238U/235U) provide a more direct indicator of these geochemical reactions controlling U mobility. U(VI) reduction induces a strong fractionation of U isotopes, shifting the U isotopes of the remaining U(VI) and producing U(IV) with a distinct isotopic composition. Our published laboratory studies imply that U(VI) adsorption, while impacting U concentrations, has only a minor, consistent effect on U isotopes. Adsorption to various aquifer minerals induces an average isotopic fractionation of -0.15‰ with the adsorbed U(VI) isotopically lighter than coexisting aqueous U(VI). Studies using U isotope data to assess U(VI) reduction and U(IV) oxidation must consider adsorption as a lesser, but significant, isotope fractionation process. Published field studies demonstrate that U(IV) oxidation can be detected via observation of changes in U isotopes. The incorporation of remobilized U(IV) with a high 238U/235U ratio into the aqueous U(VI) pool produces an increase in 238U/235U of aqueous U(VI). However, microbial, geochemical, and hydrologic complexities can complicate the use of 238U/235U in tracking U(IV) oxidation and U(VI) reduction. Through inclusion of 238U/235U into a multicomponent reactive transport modeling framework, we track U removal during both natural and biostimulated U(VI) reduction and U remobilization during U(IV) oxidation to develop 238U/235U as a simple, reliable tool for analyzing U geochemical behavior. Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2020-12-01 The student, Noah Jemison, accepted the attached license on 2018-08-24 at 16:28. The student, Noah Jemison, submitted this Dissertation for approval on 2018-08-24 at 16:38. This Dissertation was approved for publication on 2018-08-27 at 14:58. DSpace SAF Submission Ingestion Package generated from Vireo submission #12982 on 2019-02-08 at 11:37:35 Made available in DSpace on 2019-02-08T18:39:38Z (GMT). No. of bitstreams: 2 JEMISON-DISSERTATION-2018.pdf: 5008555 bytes, checksum: 29b0e3b7cb13798123d3d74d8046685c (MD5) LICENSE.txt: 4209 bytes, checksum: 9b336a163c3681ba90343a1ffd6de115 (MD5) Previous issue date: 2018-08-27 Embargo set by: Seth Robbins for item 109911 Lift date: 2021-02-08T18:40:00Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system Embargo set by: Seth Robbins for item 109911 Lift date: 2021-02-08T18:42:23Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system Embargo set by: Seth Robbins for item 109911 Lift date: 2021-02-08T18:43:54Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system Embargo set by: Seth Robbins for item 109911 Lift date: 2021-02-08T18:44:50Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system Limited Restriction Lifted for Item 109911 on 2021-02-09T10:15:38Z. application/pdf http://hdl.handle.net/2142/102885 en Copyright 2018 Noah Jemison 238U/235U, U(VI) reduction, U(IV) oxidation Uranium isotopes as indicators of uranium immobilization and remobilization in contaminated aquifer settings text text Geology Geology University of Illinois at Urbana-Champaign Dissertation Ph.D.