Radiological characterisation of disposed phosphogypsum in Brazil: evaluation of the occupational exposure and environmental impact

Abstract

Phosphogypsum, a waste by-product derived from the wet process production of phosphoric acid, represents a serious problem facing the phosphate industry in Brazil. This by-product (mainly calcium sulphate dihydrate) precipitates during the reaction of sulphuric acid with phosphate rock and is stored at a rate of about 4x10(6) kg per day on several piles in Cubatão, Brazil. Contents of natural radionuclides from thorium and uranium series were measured in Brazilian phosphogypsum samples from disposal piles, using high-resolution gamma ray spectrometry and instrumental neutron activation analysis (NAA). These phosphogypsum piles present a potential threat to the surrounding environment and to the individual occupationally exposed. The results obtained in this study show that radionuclides, although present in relatively high concentrations in phosphogypsum, do not imply in significant doses for individuals occupationally exposed. The results obtained for the water activity in the monitor wells showed that the run-off of the piles is influenced by the activity present in the piles, giving indication of a possible groundwater contamination. Sediments from rivers in the area of influence of the pile presented higher concentrations of 238U and 232Th when compared with reference values.

Trace Element Contaminants and Radioactivity from Phosphate Fertiliser

“…E.g. more than 1/3 of the total annual phosphogypsum production (4.5 Mt) in Brazil is used as soil amendment even though the measured activity often exceeds the USEPA guideline of 370 Bq/kg (Santos et al 2006;Saueia and Mazzilli 2006;USEPA 2005).…”

Measuring and modelling the radiological impact of a phosphogypsum deposition site on the surrounding environment / Mjerenje i modeliranje radiološkog utjecaja odlagališta fosfogipsa na okoliš

“…The results of radionuclide transfer from grass to animal products are shown in Table 4 Due to the lack of data on natural radionuclides in local meat and milk, we compared our results data from other sources and established that they are reasonably similar (40)(41)(42). Also, they are below the internationally maximum permitted levels of radioactive contamination in foodstuffs and below or similar to the proposed safe values of radionuclides in food and feed (43).…”

“…This study covered measurements of activity concentrations for natural radionuclides ( 238 U, 235 U, 232 Th,226 Ra, 210 Pb, and 40 K) in soil, PG, and grass samples. Results showed that activity concentrations in PG vary with the origin of the phosphate rock used in production, which is in accordance with investigations performed in other countries.…”

“…Using values obtained from measurements of activity concentrations of 226 Ra, 232 Th, and 40 K, the radium equivalent . These results are in accordance with earlier direct dose rate measurements conducted on the same deposition site using electronic dosimeters (11).…”

Avaliação da exposição externa em residência construída com fosfogesso

“…Atualmente, a maior parte do fosfogesso produzido é armazenada em pilhas ao ar livre, o que exige monitoração, para a verificação de possível contaminação atmosférica, poluição das águas subterrâneas, emanação e exalação de radônio e exposição direta à radiação gama (Santos et al, 2006;Silva et al, 2005).…”