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Natural radioactivity in phosphate rock, phosphogypsum and phosphate fertilizers in Brazil

  • D. I. T. Fávaro
Article

Summary

Phosphate deposits are generally characterized by enhanced radionuclide concentrations compared to natural levels. The mining and processing of this phosphate ore redistribute radionuclides throughout the environment and introduce them into phosphoric acid and phosphogypsum. Phosphoric acid is the starting material for triple superphosphate (TSP), single superphosphate (SSP), monoammonium phosphate (MAP), diammonium phosphate (DAP), NPK fertilizers and di-calcium phosphate (DCP). Contents of natural radionuclides from thorium and uranium series, <Superscript>226</Superscript>Ra, <Superscript>210</Superscript>Pb and <Superscript>228</Superscript>Ra, were measured in Brazilian igneous phosphate rock, phosphoric acid, phosphogypsum and phosphate fertilizer samples, using high-resolution gamma-spectrometry. Neutron activation analysis was used for the determination of U and Th in the same samples. The fertilizers samples which are derived directly from phosphoric acid, MAP and DAP, presented activity concentrations around the detection limits of the counting system for <Superscript>226</Superscript>Ra (&lt;5.0 Bq<Superscript> .</Superscript> kg<Superscript>-1</Superscript><Superscript>), for 228</Superscript>Ra (&lt;3.0 Bq<Superscript> .</Superscript> kg<Superscript>-1</Superscript>) and for <Superscript>210</Superscript>Pb (&lt;19 Bq<Superscript> .</Superscript> kg<Superscript>-1</Superscript>). As for U and Th, the concentrations found in MAP and DAP are more significant, up to 374 and 250 Bq<Superscript> .</Superscript> kg<Superscript>-1</Superscript>, respectively. SSP, TSP and NPK, which are obtained by mixing phosphoric acid with different amounts of phosphate rock and NH<Subscript>3</Subscript>, presented higher concentrations of radionuclides, up to 871 Bq<Superscript> .</Superscript> kg<Superscript>-1</Superscript> for <Superscript>226</Superscript>Ra, 283 Bq<Superscript> .</Superscript> kg<Superscript>-1</Superscript> for <Superscript>228</Superscript>Ra, 1255 Bq<Superscript> .</Superscript> kg<Superscript>-1</Superscript> for <Superscript>210</Superscript>Pb, 413 Bq<Superscript> .</Superscript> kg<Superscript>-1</Superscript> for U and 538 Bq<Superscript> .</Superscript> kg<Superscript>-1</Superscript> for Th.

Keywords

Radionuclide Phosphoric Acid Phosphate Rock Phosphate Fertilizer Phosphogypsum 

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Copyright information

© Springer-Verlag/Akadémiai Kiadó 2005

Authors and Affiliations

  • D. I. T. Fávaro
    • 1
  1. 1.Laborat&#243;rio de An&#225;lise por Ativa&#231;&#227;o Neutr&#244;nica, Instituto de Pesquisas Energ&#233;ticas e Nucleares

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