Understanding the transport and retention of radionuclides in the environment is important for protecting freshwater supplies and minimizing impact to biologic systems. Technetium-99 (Tc⁹⁹) is a radionuclide of interest due to its long half-life (2.13 x 10⁵ years) and toxicity. In the form of pertechnetate (TcO₄⁻), Tc is expected to move nearly unretarded in the subsurface. Under reducing conditions Tc can precipitate in low solubility Tc oxide (TcO₂·nH₂O) and/or Tc sulfide (Tc₂S[subscript x]) phases.
The studies presented in this dissertation investigate the physiochemical mechanisms for the transport and retention of Tc. Transport studies determined that TcO₄⁻ would move at pore water velocity in unsaturated sediments. Geochemical studies of contaminated sediments determined that nearly ~ 25 % of the total Tc was retained in phases associated with iron oxide and aluminosilicate minerals, thus reducing the mobility of Tc. Studies of Tc₂S[subscript x] mineral phases, generated using nano Zero Valent Iron (nZVI) and sulfide (HS-) in sediments, determined that Tc could be stabilized in mineral phases as Tc₂S[subscript x] that were slower to reoxidize than TcO₂·nH₂O phases. / Graduation date: 2013 / Access restricted to the OSU Community at author's request from Feb. 14, 2013 - Feb. 14, 2014
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36911 |
| Date | 14 February 2014 |
| Creators | Jansik, Danielle P. |
| Contributors | Istok, Jonathan |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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