Studies of radioactivity and heavy metals in phosphate fertilizer

The enormous utilization of phosphate rock and super phosphate derived from it have the potential of being an important factor in the contamination of aquifers with alpha emitting radionuclides and heavy metals. Both rock phosphate and super phosphate contain substantial levels of natural uranium, amounting to hundreds of ppm. Our study has shown that whereas the uranium series in phosphate rock in nearly in secular equilibrium, in super phosphate the 226Ra and its progeny are depleted by 60-70%. This is a result of the chemical processing of the rock phosphate. On the other hand the super phosphate is much more soluble and can be expected to release its radionuclides to the environment more rapidly than rock phosphate. The present study explores the release of radioisotopes and heavy metals from phosphate fertilizers. Extensive analytical use has been made of a germanium well-detector/Compton suppression system. (author). 9 refs., 4 tabs