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 p hosphorous retention capacity which leads to pollution of surface wate r bodies in the region. Application of bauxite mining residues (termed ''red mud'') to vegetable and crops has been proposed as a solution t o increase the phosphorous and water retention and thereby reduce the leaching of nutrients. The thorium and radium-226 concentrations in th e ''red mud'' residues are in excess of 1 kBq/kg and 300 Bq/kg, respec tively. Potentially, the use of these residues on agricultural land co uld result in increased levels of radionuclides in food crops grown in amended soils. The transfer of long-lived radionuclides of both the n atural thorium and uranium series to a variety of vegetable crops grow n under controlled conditions is investigated. The effects of varying the rates of application of ''red mud'' and phosphate fertilisers on r adionuclide uptake are studied. It has been shown previously that fall out caesium-137 in sandy soils of the region transfers readily to food and grazing crops. Some of the parameters which influence that transf er are also examined.