Bioaccumulation of radionuclides

Background

Many animal and plant species of the Alligator Rivers Region are used as food by humans, particularly by the Aboriginal inhabitants of the region. The potential for uptake of radionuclides by aquatic species such as fish, mussels and aquatic plants needs to be assessed for the surface water transport pathway of radionuclides. In addition, uptake by fruits and vegetables growing on the minesite can be an important pathway for bioaccumulation of radionuclides after rehabilitation is completed.

Current research projects

Identification of traditional Aboriginal foods for radiological assessment

The project is undertaken with the assistance of local Aboriginal organisations and individuals. The project consists of three parts (i) the identification, collection and cataloguing of traditional Aboriginal foods that are consumed in the Alligator Rivers Region (ARR), (ii) recognition of the preparation techniques used for traditional foods and (iii) conduct a radiological assessment of the foods identified using alpha spectrometry and high resolution gamma spectrometry techniques.

Project leader: Bruce Ryan.

Radiological impact arising from uptake by freshwater mussels and fish of Mudginberri Billabong

Freshwater mussels of the Magela Creek system are known to have a high bioaccumulation factor for radium. For this reason consumption of mussels may potentially be the most important pathway for radiological impact arising from inputs of mine-derived waters in the Alligator Rivers Region. Consequently, considerable research into bioaccumulation of radionuclides by mussels has been undertaken by eriss over the past decades. Fish have been found to accumulate radionuclides to a much lesser extent than mussels. Hence, fish have only been collected and analysed every 2nd year to provide ongoing public re-assurance.

Project leader: Bruce Ryan.

Bioaccumulation of radionuclides in terrestrial plants on rehabilitated landforms

Over the last 25 years the Supervising Scientist Division (SSD) has gathered radiological data on bush foods throughout the Alligator Rivers Region (ARR) in the Northern Territory. Early studies were focused on aquatic animal and plant species due to the identified importance of the aquatic transport pathway for bioaccumulation of radionuclides in bush foods during the operational phase of uranium mining operations in the region. Following rehabilitation of the Ranger uranium mine site there may be a shift towards terrestrial food sources that are growing in the vicinity of the former mine.

It can reasonably be assumed that the highest dose rates to humans will be received from the consumption of foods from the vicinity of the contamination source. Samples of bushtucker and associated soils are being analysed to determine radionuclide uptake in plants from the Ranger Land Application Areas (which are areas on the mine site that are irrigated with mine waters) and from other relevant mine-impacted areas. Total and leachable activity concentrations have been measured in some of the soils to determine the bioavailable fraction of the radionuclides, reduce the variability of derived transfer factors (which is the ratio of plant to soil radionuclide activity concentration) and enable a more reliable dose prediction to be made for the ingestion of terrestrial bushfoods.

Project leaders: Peter Medley and Bruce Ryan.

Some relevant publications

Ryan B, Bollhöfer A, Martin P, 2008. Radionuclides and metals in freshwater mussels of the upper South Alligator River, Australia. Journal of Environmental Radioactivity 99, 509-526.

Ryan B, Martin P & Iles M 2005. Uranium-series radionuclides in native fruits and vegetables of northern Australia. Journal of Radioanalytical and Nuclear Chemistry 264(2), 407-412.

Martin P & Ryan B 2004. Natural-series radionuclides in traditional Aboriginal foods in tropical northern Australia: a review. TheScientificWorldJOURNAL 4, 77–95.
Martin P, Hancock GJ, Johnston A & Murray AS 1998. Natural-series radionuclides in traditional north Australian Aboriginal foods. Journal of Environmental Radioactivity 40, 37-58.

Pettersson HBL, Hancock G, Johnston A & Murray AS 1993. Uptake of uranium and thorium series radionuclides by the waterlily, Nymphaea violacea. Journal of Environmental Radioactivity 19, 85–108.

Johnston A, Murray AS, Marten R & Martin P 1987. The transport and deposition of radionuclides discharged into creek waters from the Ranger uranium mine. Open file record 45, Supervising Scientist for the Alligator Rivers Region, Canberra. Unpublished paper.