STUDIES OF NATURAL RADIONUCLIDES AVAILABILITY IN NORM (NATURALLY OCCURRING RADIOACTIVE MATERIALS) SITES
1) Radioecological studies on the phosphogypsum stock pile of Barreiro
A phosphogypsum (PG) waste pile resulting from the production of phosphate fertilizer industry from the wet process of phosphate rock (phosphorite) is located at Lavradio-Barreiro, southern margin of Tejo estuary. PG may contain large amounts of radionuclides of the uranium series (e.g., 226Ra and 210Pb) and trace elements, which can be toxic to the environment. In this work a first integrated approach of this waste material and environmental samples is performed including: (i) the characterization of PG and the surrounding soil in terms of natural radionuclides, and chemical and crystalline composition; and (ii) the assessment of radionuclides transfer to plants (fam.Plantaginaceae, Plantago sp.) and mosses (Bryum sp.) growing naturally on the PG pile.
Activity concentrations of main radionuclides measured in herbaceous plants, mosses and the underlying substrate of phosphogypsum.
2) In situ radioecological experiment in the vicinity of a sealed uranium mine dump site (Barragem Velha, Urgeiriça)
A small in situ scale experiment for determination of U and 226Ra bioavailability was performed in the former uranium mining site of Urgeriça, located at the center of Portugal. To enhance the uranium availability citric acid solutions with different concentrations (10 and 20 mmol L-1) were applied on the top soil cover with a fern field (Figure below). After laboratory treatment soil and plant samples were analysed by gamma spectrometry. The analyses of the uranium concentration in plant tissue and soil solution are still ongoing.
Adding citric acid to soil on a fern field.
- Corisco JAG, Mihalik J, Madruga MJ, Prudêncio MI, Marques R, Santos M, Reis M (2017). Natural Radionuclides, Rare Earths and Heavy Metals Transferred to the Wild Vegetation Covering a Phosphogypsum Stockpile at Barreiro, Portugal. Water Air and Soil Pollution 228: 235. doi:10.1007/s11270-017-3413-6.