title: A dosimetric model for determining the effectiveness of soil covers for phosphogypsum waste piles.
abstract: Phosphogypsum (PG) is a by-product of the phosphoric acid production process that contains high concentrations of U-series radionuclides. PG piles formed during the last 30 years cover about 1,200 hectares and are located close to the town of Huelva (Spain) on a salt-marsh. The regional government of Andalusia restored the area beginning in 1990 by covering it with a 25-cm-thick layer of natural soil. With this restoration, the external gamma-dose rate in the zone has decreased drastically, approaching near environmental background values. This conclusion is based on results obtained through in-situ monitoring measurements and through a dosimetric model developed for that particular radiation source. As the model uses average parameters of the studied site, its output does not show a correlation point by point with the in-situ monitoring measurements. However, a good agreement is observed in average values over the covered piles. The model gives an average dose rate of 0.41 mGy y(-1) and the in situ monitoring 0.40 mGy y(-1). Based on this model, it is possible to calculate the necessary thickness of soil to reduce the dosimetric contribution from a similar extension of PG until the desired level is reached. In our conditions, in a 25-cm-thick soil, about 0.19 mGy y(-1) is the increase produced by the PG layer in relation to an infinitum soil layer. Consequently, no radiological concern exists in the restored zones with respect to the external gamma radiation.
authors.affiliation: Department  Física Aplicada, E.P.S. La Rábida, Universidad de Huelva, Spain.
authors.forename: J L
authors.initials: JL
authors.lastname: Más
authors.forename: J P
authors.initials: JP
authors.lastname: Bolívar
authors.forename: R
authors.initials: R
authors.lastname: García-Tenorio
authors.forename: J L
authors.initials: JL
authors.lastname: Aguado
authors.forename: E G
authors.initials: EG
authors.lastname: San Miguel
authors.forename: J
authors.initials: J
authors.lastname: González-Labajo
mesh_terms: D002133:Calcium Sulfate; D006801:Humans; D007220:Industrial Waste; D008954:Models, Biological; D010758:Phosphorus; D011829:Radiation Dosage; D012990:Soil Pollutants, Radioactive; D013030:Spain
chemical_list: D007220:Industrial Waste; D012990:Soil Pollutants, Radioactive; C077769:phosphogypsum; D010758:Phosphorus; D002133:Calcium Sulfate