Plutonium and other radionuclides persist across marine-to-terrestrial ecotopes in the Montebello Islands sixty years after nuclear tests.

Since the 1956 completion of nuclear testing at the Montebello Islands, Western Australia, this remote uninhabited island group has been relatively undisturbed (no major remediations) and currently functions as high-value marine and terrestrial habitat within the Montebello/Barrow Islands Marine Conservation Reserves. The former weapons testing sites, therefore, provide a unique opportunity for assessing the fate and behaviour of Anthropocene radionuclides subjected to natural processes across a range of shallow-marine to island-terrestrial ecological units (ecotopes). We collected soil, sediment and biota samples and analysed their radionuclide content using gamma and alpha spectrometry, photostimulated luminescence autoradiography and accelerator mass spectrometry. We found the activity levels of the fission and neutron-activation products have decreased by ~hundred-fold near the ground zero locations. However, Pu concentrations remain elevated, some of which are high relative to most other Australian and international sites (up to 25,050 Bq kg-1 of 239+240+241Pu). Across ecotopes, Pu ranked from highest to lowest in the following order: island soils > dunes > foredunes > marine sediments > and beach intertidal zone. Low values of Pu and other radionuclides were detected in all local wildlife tested including endangered species. Activity concentrations ranked (highest to lowest) terrestrial arthropods > terrestrial mammal and reptile bones > algae > oyster flesh > whole crab > sea turtle bone > stingray and teleost fish livers > sea cucumber flesh > sea turtle skin > teleost fish muscle. The three detonations (one from within a ship and two from 30 m towers) resulted in differing contaminant forms, with the ship detonation producing the highest activity concentrations and finer more inhalable particulate forms. The three sites are distinct in their 240/239Pu and 241/239Pu atom ratios, including the Pu transported by natural process or within migratory living organisms.

In vitro dissolution studies of uranium bearing material in simulated lung fluid.

Inhaled uranium (U) bearing material will partially dissolve in the fluid lining of the lung, followed by a combination of retention, re-distribution, and excretion of the U. The rate of dissolution influences the retention time at the site of deposition, and the extent to which the material is available for re-distribution to other tissues. The consequential radiation dose is dependent upon the material distribution in the body and the exposure time to various tissues. The International Commission on Radiological Protection, ICRP 66 [International Commission on Radiological Protection (ICRP), 1994. Human Respiratory Tract Model for Radiological Protection. ICRP Publication 66] recommends the use of experimentally determined solubility coefficients in dose modelling. Material specific absorption parameters allow for better dose estimation than using ICRP default values for F (fast), M (moderate) and S (slow) classifications of U compounds. In vitro dissolution tests were carried out on U material collected from two U mines located in Australia. A static technique was designed in which particle samples were sandwiched between two 0.1-mum pore size membrane filters. The filter sandwich was exposed to a solvent (simulated lung fluid) for selected time intervals, at controlled test conditions for temperature and pH. The collected solution was analysed for U concentration using ICP-MS. The resulting dissolution curves were fitted with a double or triple exponential equation to determine the dissolution coefficients.

Method design and validation for the determination of uranium levels in human urine using high-resolution alpha spectrometry.

Quantification of uranium in human urine is a valuable technique for assessing occupational and public exposure to uranium. A reliable method has been developed and validated in the ARPANSA Radiochemistry Laboratory by means of standard radiochemical separation and purification techniques and measurement using high-resolution alpha spectrometry. This method can be used to evaluate the levels of naturally occurring 234U, 235U and 238U in urine. Method design and validation is the process of defining an analytical requirement, and then confirming that the method under consideration has performance capabilities consistent with what the application requires. The method was designed to measure levels down to 2 mBq/day of total uranium, corresponding to approximately 1/100th of the annual committed effective dose of 20 mSv. Validation tests were developed to assess selectivity, accuracy, recovery and quantification of uncertainty. The radiochemical recovery of this method was measured using (232)U tracer. The typical minimum detectable concentration for total uranium for 24-h urine samples is approximately 0.6 mBq/day or 0.019 microg/day.