Browsing by Author "Angel, BM"

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    Analysis of uranium, thorium and radium radioisotopes in coal seam gas associated water samples
    (South Pacific Environmental Radioactivity Association, 2018-11-06) Maizma, S; Chellappa, J; Zawadzki, A; Apte, S; King, J; Jarolimek, C; Angel, BM
    The Australian coal seam gas (CSG) industry, located mainly in eastern Australia, has grown significantly over the last decade and is now a significant contributor to natural gas production in Australia. CS6 extraction involves drilling boreholes across landscapes which intersect with coal seams. Gas is then flowed to the surface along with associated produced waters. In order to increase gas production, some wells are subjected to hydraulic fracturing which involves pumping water, chemicals and a proppant into the coal seams. The resulting flow-back waters are then collected at the surface prior to treatment and disposal. There are significant public concerns about the water quality of flow-back and produced waters associated with CSG operations, in particular the concentration of geogenic contaminants including radioisotopes such as 226Ra and 222Ra. In order to address these concerns, accurate data on water quality needs to be collected. CSG waste waters are complex, saline matrices and sensitive, robust analytical methods are required to reliably quantify the concentrations of contaminants including radioisotopes ln this work, radioisotopes of uranium, thorium and radium were analysed in CSG flow-back and produced waters samples collected from CSG bores located in Central Queensland, Australia. The water samples were processed for the determination of 233U, 238U, 228Th, 230Th, 232Th, 226Ra activity concentrations by alpha-particle spectrometry and 222Ra by gamma-ray spectrometry. GSG associated water consist of high concentrations of total dissolved solids (TDS) ranging from 800 to 10,000 mg/L. Such high salinity levels pose difficulties for the measurement of the radioisotopes of interest, resulting in low sample recoveries and poor resolution alpha spectra. This paper presents radiochemical techniques used to reduce the complex sample matrix effects in analysing CSG associated water samples. Manganese dioxide co-precipitation technique was chosen to concentrate the elements of interest, followed by the isolation of uranium and thorium using UTEVA (Eichrom) resin. The determination of 222Ra by alpha spectrometry was found to be challenging due to low sample recoveries and poor alpha spectra resolutions. This was overcome by diluting the samples in large volumes prior to lead sulphate co-precipitation, which isolates radium and barium from other metals in the samples. The developed radiochemical technique was suitable and robust for determining the radioisotopes of interest in CSG associated water samples.
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    Metal speciation and potential bioavailability changes during discharge and neutralisation of acidic drainage water
    (Elsevier, 2014-05) Simpson, SL; Vardanega, CR; Jarolimek, C; Jolley, DF; Angel, BM; Mosely, LM
    The discharge of acid drainage from the farm irrigation areas to the Murray River in South Australia represents a potential risk to water quality. The drainage waters have low pH (2.9–5.7), high acidity (up to 1190 mg L−1 CaCO3), high dissolved organic carbon (10–40 mg L−1), and high dissolved Al, Co, Ni and Zn (up to 55, 1.25, 1.30 and 1.10 mg L−1, respectively) that represent the greatest concern relative to water quality guidelines (WQGs). To provide information on bioavailability, changes in metal speciation were assessed during mixing experiments using filtration (colloidal metals) and Chelex-lability (free metal ions and weak inorganic metal complexes) methods. Following mixing of drainage and river water, much of the dissolved aluminium and iron precipitated. The concentrations of other metals generally decreased conservatively in proportion to the dilution initially, but longer mixing periods caused increased precipitation or adsorption to particulate phases. Dissolved Co, Mn and Zn were typically 95–100% present in Chelex-labile forms, whereas 40–70% of the dissolved nickel was Chelex-labile and the remaining non-labile fraction of dissolved nickel was associated with fine colloids or complexed by organic ligands that increased with time. Despite the different kinetics of precipitation, adsorption and complexation reactions, the dissolved metal concentrations were generally highly correlated for the pooled data sets, indicating that the major factors controlling the concentrations were similar for each metal (pH, dilution, and time following mixing). For dilutions of the drainage waters of less than 1% with Murray River water, none of the metals should exceed the WQGs. However, the high concentrations of metals associated with fine precipitates within the receiving waters may represent a risk to some aquatic organisms. © 2013, Elsevier Ltd.