Contaminant release, mixing and microbial fluctuations initiated by infiltrating water within a replica field-scale legacy radioactive waste trench

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dc.contributor.authorKinsela, ASen_AU
dc.contributor.authorPayne, TEen_AU
dc.contributor.authorBligh, MWen_AU
dc.contributor.authorVázquez-Campos, Xen_AU
dc.contributor.authorWilkins, MRen_AU
dc.contributor.authorComarmond, MJen_AU
dc.contributor.authorRowling, Ben_AU
dc.contributor.authorWaite, TDen_AU
dc.date.accessioned2023-11-30T21:59:35Zen_AU
dc.date.available2023-11-30T21:59:35Zen_AU
dc.date.issued2022-12-10en_AU
dc.date.statistics2022-08-29en_AU
dc.description.abstractNumerous legacy near-surface radioactive waste sites dating from the mid 20th century have yet to be remediated and present a global contamination concern. Typically, there is insufficient understanding of contaminant release and redistribution, with invasive investigations often impractical due to the risk of disturbing the often significantly radiotoxic contaminants. Consequently, a replica waste trench (~5.4 m3), constructed adjacent to a legacy radioactive waste site (Little Forest Legacy Site, LFLS), was used to assist our understanding of the release and mixing processes of neodymium (Nd) — a chemical analogue for plutonium(III) and americium(III), two significant radionuclides in many contaminated environments. In order to clarify the behaviour of contaminants released from buried objects such as waste containers, a steel drum, representative of the hundreds of buried drums within the LFLS, was placed within the trench. Dissolved neodymium nitrate was introduced as a point-source contaminant to the base of the trench, outside the steel drum. Hydrologic conditions were manipulated to simulate natural rainfall intensities with dissolved lithium bromide added as a tracer. Neodymium was primarily retained both at its point of release at the bottom of the trench (>97 %) as well as at a steel container corrosion point, simulated through the emplacement of steel wool. However, over the 8-month field experiment, advective mixing initiated by surface water intrusions rapidly redistributed a small proportion of Nd to shallower waters (~1.5–1.7 %), as well as throughout the buried steel drum. Suspended particulate forms of Nd (>0.2 μm) were measured at all depths in the suboxic trench and were persistent across the entire study. Analyses of the microbial communities showed that their relative abundances and metabolic functions were strongly influenced by the prevailing geochemical conditions as a result of fluctuating water depths associated with rainfall events. The site representing steel corrosion exhibited divergent biogeochemical results with anomalous changes (sharp decrease) observed in both dissolved contaminant concentration as well as microbial diversity and functionality. This research demonstrates that experimental trenches provide a safe and unique method for simulating the behaviour of subsurface radioactive contaminants with results demonstrating the initial retention, partial shallow water redistribution, and stability of particulate form(s) of this radioactive analogue. These results have relevance for appropriate management and remediation strategies for the adjacent legacy site as well as for similar sites across the globe. © 2022 Elsevier B.V.en_AU
dc.description.sponsorshipThis work was funded through the Australian Research Council Discovery Project scheme (DP210103727), as well as the Australian Nuclear Science and Technology Organisation (ANSTO) and the University of New South Wales (UNSW). The authors also acknowledge the ANSTO team for; excavating the replica trench (ANSTO Asset Management and Services group, Matthew Skuse and Adam Weston), site-wide geochemical, logistical advice and fieldwork assistance (including Dr. Catherine Hughes, Dr. Dioni Cendon, Mr. Stuart Hankin, Mr. Chris Dimovski, Ms. Jennifer Harrison, Mr. Henri Wong, Mr. Chris Vardanega, Mr. Sangeeth Thiruvoth, Ms. Adella Silitonga, Ms. Kerry Wilsher and Dr. Mathew Johansen), along with the ANSTO Safety Assurance Committee, Radiation Protection Advisers and Work Health and Safety team for safety advice. MRW acknowledges the support of the Australian Federal Government NCRIS scheme, via Bioplatforms Australia. MRW and XV-C acknowledge support from the New South Wales State Government RAAP scheme and the UNSW RIS scheme.en_AU
dc.identifier.articlenumber158241en_AU
dc.identifier.citationKinsela, A. S., Payne, T. E., Bligh, M. W., Vázquez-Campos, X., Wilkins, M. R., Comarmond, M. J., Rowling, B., & Waite, T. D. (2022). Contaminant release, mixing and microbial fluctuations initiated by infiltrating water within a replica field-scale legacy radioactive waste trench. Science of The Total Environment, 851, Part 1, 158241. doi:10.1016/j.scitotenv.2022.158241en_AU
dc.identifier.issn0048-9697en_AU
dc.identifier.issuePart 1en_AU
dc.identifier.journaltitleScience of The Total Environmenten_AU
dc.identifier.urihttps://doi.org/10.1016/j.scitotenv.2022.158241en_AU
dc.identifier.urihttps://apo.ansto.gov.au/handle/10238/15252en_AU
dc.identifier.volume851en_AU
dc.language.isoenen_AU
dc.publisherElsevier B. V.en_AU
dc.relation.urihttps://doi.org/10.1016/j.scitotenv.2022.158241en_AU
dc.subjectANSTOen_AU
dc.subjectRadioactive waste disposalen_AU
dc.subjectUnderground disposalen_AU
dc.subjectContaminationen_AU
dc.subjectRadioactive wastesen_AU
dc.subjectEnvironmenten_AU
dc.subjectBromidesen_AU
dc.subjectNeodymiumen_AU
dc.titleContaminant release, mixing and microbial fluctuations initiated by infiltrating water within a replica field-scale legacy radioactive waste trenchen_AU
dc.typeJournal Articleen_AU
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