Browsing by Author "Gückel, K"

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    Correction: Emerging investigator series: a holistic approach to multicomponent EXAFS: Sr and Cs complexation in clayey soils
    (Royal Society of Chemistry, 2021-07-13) Bots, P; Comarmond, MJ; Payne, TE; Gückel, K; Lunn, RJ; Rizzo, L; Schellenger, AEP; Renshaw, JC
    Correction for ‘Emerging investigator series: a holistic approach to multicomponent EXAFS: Sr and Cs complexation in clayey soils’ by Pieter Bots et al., Environ. Sci.: Processes Impacts, 2021, DOI: 10.1039/D1EM00121C. - Open Access CC-BY
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    Emerging investigator series: a holistic approach to multicomponent EXAFS: Sr and Cs complexation in clayey soils
    (Royal Society of Chemistry, 2021-06-21) Bots, P; Comarmond, MJ; Payne, TE; Gückel, K; Lunn, RJ; Rizzo, L; Schellenger, AEP; Renshaw, JC
    Strontium and caesium are fission products of concern at many nuclear legacy sites and Cs is additionally a significant consideration at sites in the aftermath of nuclear accidents and incidents. Such sites require long-term management to minimize the risk of such contaminants to the environment and the public. Understanding the geochemical speciation of Sr and Cs in situ in the soils and groundwater is essential to develop engineered management strategies. Here we developed and utilized a comprehensive approach to fitting the EXAFS of Sr and Cs adsorption to single mineral phases and a composite clayey soil. First, a shell-by-shell fitting strategy enabled us to determine that Sr surface complexes involve the formation of bidentate edge sharing complexes with anatase and illite-smectite, and form at the silicon vacancy sites at the kaolinite basal surfaces. Cs surface complexes form at the silicon vacancy sites at the illite-smectite and kaolinite basal surfaces. Second, using a subsequent holistic approach we determined the predominance of these complexes within a composite clayey soil. Sr was dominated by complexation with illite-smectite (72–76%) and to a lesser extent with kaolinite (25–30%) with negligible complexation with anatase, while Cs complexed roughly equally to both illite-smectite and kaolinite. The presented approach to fitting EXAFS spectra will strengthen predictive modelling on the behaviour of elements of interest. For example, the details on Sr and Cs speciation will enable predictive modelling to characterise their long-term behaviour and the design and validation of evidence-based engineering options for long-term management of nuclear legacy sites. © Royal Society of Chemistry 2024 - Open Access CC-BY
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    Radionuclide sorption studies of Co, Cs and Sr onto soils from an Australian legacy radioactive waste site
    (South Pacific Environmental Radioactivity Association, 2012-10-18) Gückel, K; Comarmond, MJ; Payne, TE; Chong, E; Mokhber-Shahin, L
    This paper discusses results of radionuclide sorption studies on a soil profile taken from a low level radioactive waste site in South Eastern Australia, known as the Little Forest Burial Ground. Low level radioactive waste was buried at this site in a series of shallow trenches in the 1960s, and the site has been the focus of a field study in recent years. Measurable amounts of Co-60, Sr-90, Cs-137 and traces of actinides have been observed at this legacy waste site in some soils, groundwater and vegetation samples taken in close proximity to the disposal area. The sorption of Co, Cs and Sr was studied at four depth intervals from one corehole located near the trenches using radioactive tracers and a batch sorption method. Strong sorption was observed for Cs over the entire pH range studied, whereas the sorption of Co and Sr on the soils was pH dependent with sorption edges between pH 3 and pH 6. Distribution coefficients (Kd values) for Cs sorption were similar for each soil over the entire pH range, with variations of less than one order of magnitude between samples. However, the Kd values for Sr and Co sorption varied over two and three orders of magnitude, respectively, over the pH range studied. The bulk mineralogy of the soils was found to be similar with quartz, kaolinite and interstratified illite/smectite to be the main mineralogical phases with iron oxides and anatase as minor minerals in some soils. The BET surface areas of the bulk samples varied from 27 m2/g to 47 m2/g and no strong correlation of surface area with sorption was observed. The CEC of the bulk samples range between 10 and 24 cmol/kg. The CEC of the clay fractions were significantly higher, ranging from 21 to 34 cmol/kg and 34 to 55 cmol/kg for the < 2 μm and < 0.2 μm fractions, respectively. Further studies to elucidate the role of the various minerals with respect to sorption are in progress in order to assess the key site characteristics governing contaminant release and transport.