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Research Report 11
Martin P, Hancock GJ, Johnston A & Murray AS
Supervising Scientist 1995
ISSN 0810-9966
Activity concentrations of the radionuclides 210Pb, 210Po, 226Ra, 238U, 234U, 232Th and 230Th were measured in edible flesh of a number of traditional Aboriginal food items from the Magela and Cooper Creek systems in the tropical Northern Territory of Australia. Some results for 227Ac were also obtained. Food items studied were fish, buffalo, pig, magpie goose, filesnake, goanna, turtle, freshwater shrimp, freshwater crocodile and two types of plant roots. Water and soil activity concentrations were also measured to enable the calculation of concentration factors.
For most edible flesh samples, activity concentrations followed the approximate order: 210Po >> [226Ra~210Pb] >[234U~238U]>[230Th~232Th]. The 210Po/210Pb activity ratio was particularly high (greater than 100) for pig flesh. The highest soft tissue activity concentration recorded was 45000 ± 2000 mBq/kg wet weight for 210Po in one sample of turtle liver.
Concentration factors for fish species fall into three groups. Group 1 (bony bream and sleepy cod) had factors about five times higher than for Group 2 (eight other species including barramundi). Some smaller fish species (Group 3) are eaten whole and hence have relatively high concentration factors. Variability with location and season was small in comparison with inter-group variability. Measured factors for fish in groups 1 and 3 were generally significantly higher than IAEA default values.
Factors for turtle flesh were similar to those for fish in group 1, but were about a factor of 10 higher for liver. Factors for magpie goose, filesnake, freshwater shrimp, goanna and crocodile flesh were also of the same order as for fish in groups 1 or 2.