In this presentation, I describe results of investigations into factors contributing to migration of radionuclides at a legacy waste disposal site on the southern outskirts of Sydney, Australia. The mobility of contaminants at this site is strongly influenced by episodic rainfall events that induce dynamic changes in reduction potential in subsurface trench environment. High concentrations of dissolved ferrous iron accumulates in trench waters during dry periods with this Fe(II) oxidizing rapidly on influx of oxic rainwaters. Both the presence of surfaces and of silica appear to influence the Fe(II) oxidation kinetics with the resultant formation of iron oxyhydroxide particles critical to prevention of radionuclide migration from the site (Jones et al., 2015; Kinsela et al., 2016). The changes in groundwater chemistry are mirrored by dynamic changes in the microbial community (Vazquez-Campos et al., 2017). Mathematical models have been developed of both the Fe(II) oxidation process and the overall impact of rainfall events on contaminant mobility with these models likely to be of use in assessing possible remediation strategies. Jones, A.M., Griffin, P.J., Collins, R.N. and Waite, T.D. (2015). Ferrous iron oxidation under acidic conditions – The effect of ferric oxide surfaces. Geochimica et Cosmochimica Acta 156, 241-241. Kinsela, A.S., Jones, A.M., Bligh, M.W., Pham, A.N., Collins, R.N., Harrison, J.J., Wilsher, K.L., Payne, T.E. and Waite, T.D. (2016). Influence of dissolved silicate on Fe(II) oxidation. Environmental Science & Technology 50(21), 11663-11671. Vazquez-Campos, X., Kinsela, A.S., Bligh, M.W., Harrison, J.J., Payne, T.E. and Waite, T.D. (2017). Response of microbial community function to fluctuating geochemical conditions within a legacy radioactive waste trench environment. Applied & Environmental Microbiology 83(17), e00729-17.

Role of iron in controlling radionuclide migration at a legacy waste site exhibiting dynamic redox transitions

255th National Meeting (2018)

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