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Phosphogypsum, also called gypsum, by-product of the phosphate fertilizer industry, can be used as soil conditioner since it provides improvements in the soil-plant system. However, this by-product concentrates radionuclides of the U and Th series, present in the phosphate rock used as raw material, which can impact the environment. In order to study the bioavailability of radionuclides, samples of phosphogypsum and phosphate fertilizers (monoammonium phosphate and triple superphosphate) were analyzed. The concentration of Ra, Ra and Pb were determined by gamma spectrometry. The samples were leached with a mild EDTA-NH4 (0,05M) solution and the radionuclides present in the final solution were determined by total alpha and beta counting on a gas flow proportional counter. The percentage of extraction varied from 1.6% to 1.7% for Pb, from 0.5% to 1.4% for Ra and from 0.1% to 1.0% for the Ra in phosphogypsum samples. The low percentage of extraction obtained for the radionuclides can be partly explained by the low solubility of phosphogypsum, which ranged from 7.7% to 16%. For the monoammonium phosphate samples the percentage of extraction were less than 26% for Ra, less than 10% for Ra and less than 10% for Pb. In spite of the high solubility of 77% of monoammonium phosphate in the EDTA-NH4 (0,05M) solution, low concentrations of radionuclides were observed in the extracted solution. For the triple superphosphate samples, the percentage of extraction was 2.3% for Ra, 1.2% for Ra and 11.3% for Pb. In spite of the high solubility of 66% of triple superphosphate in the EDTA-NH4 solution, low concentrations of radionuclides were observed in the extracted solution.

Avaliação da biodisponibilidade dos radionuclídeos Ra-226, Ra-228 e Pb-210 presentes nos fertilizantes fosfatados e no fosfogesso de procedência nacional