AN INVESTIGATION OF RADIONUCLIDE UPTAKE INTO FOOD CROPS GROWN IN SOILS TREATED WITH BAUXITE MINING RESIDUES

Sandy soils of the coastal plain area of Western Australia have poor phosphorous retention capacity which leads to pollution of surface water bodies in the region. Application of bauxite mining residues (termed ''red mud'') to vegetable and crops has been proposed as a solution to increase the phosphorous and water retention and thereby reduce the leaching of nutrients. The thorium and radium-226 concentrations in the ''red mud'' residues are in excess of 1 kBq/kg and 300 Bq/kg, respectively. Potentially, the use of these residues on agricultural land could result in increased levels of radionuclides in food crops grown in amended soils. The transfer of long-lived radionuclides of both the natural thorium and uranium series to a variety of vegetable crops grown under controlled conditions is investigated. The effects of varying the rates of application of ''red mud'' and phosphate fertilisers on radionuclide uptake are studied. It has been shown previously that fallout caesium-137 in sandy soils of the region transfers readily to food and grazing crops. Some of the parameters which influence that transfer are also examined.