The Geochemistry of Natural Radionuclides in Saline Soils from Brazil Treated with Phosphogypsum Imbituba

• Published in: Water, air, and soil pollution air, and soil pollution, 2017-02, Vol.228 (2), p.1, Article 59
• Main Authors: Borges, Renata Coura, Ferreira, Alfredo Aghina, de Souza, Weber Friederichs Landim, Bernedo, Alfredo Victor Bellido
• Format: Article
• Language: English
• Subjects: Agricultural land; Agricultural practices; Analysis; Atmospheric Protection/Air Quality Control/Air Pollution; Bioavailability; Carbonates; Chemical bonds; Climate Change/Climate Change Impacts; Earth and Environmental Science; Environment; Environmental monitoring; Extraction processes; Farm buildings; Geochemistry; Hydrogeology; Iron oxides; Manganese; Methods; Organic matter; Phosphorus; Pollution; Radioisotopes; Radium isotopes; Radium radioisotopes; Saline soils; Salinity; Scientific imaging; Semiarid environments; Semiarid lands; Sodium; Software; Soil analysis; Soil Science & Conservation; Soil sciences; Soil surfaces; Spectrometry; Studies; Sulfur; Water Quality/Water Pollution
• ISSN: 0049-6979; 1573-2932
• DOI: 10.1007/s11270-016-3235-y

The soil saltiness in the Brazilian semiarid environment is a common problem caused by incorrect agricultural practices, allied to the local weather and soil condition. The use of phosphogypsum (PG) to recover these soils still is a concern since this material has in its composition natural radionuclides. An experiment was conducted to study the use of phosphogypsum to reduce the salinity and evaluate the bioavailability of radionuclides on the Brazilian semiarid region soils. The radionuclide content of phosphogypsum samples were previously analyzed by gamma spectrometry. Three differents doses of phosphogypsum were mixed with samples of surface soil in the greenhouse, and after a reaction time and irrigation, controlled soil samples + phosphogypsum underwent simple extractions based on the sequential extraction method by Tessier et al. Ra isotopes and 210 Pb in the extracted fractions were analyzed by counting alpha and beta. The higher concentration of Ra isotopes and 210 Pb were associated to residual fraction, followed by exchangeable fraction due to the low levels of carbonates, organic matter, and manganese and iron oxides. The use of phosphogypsum studied did not contribute to increase the 226 Ra activity on the analyzed soils. 226 Ra levels in phosphogypsum were lower than those recommended by the USEPA to allow the use of phosphogypsum in agricultural soils, but can contribute to the accumulation of 228 Ra and 210 Pb. The phosphogypsum Imbituba promoted a satisfactory reduction of electrical conductivity in the soils, which indicates the possibility of recovery of these soils.