Phosphogypsum from past production of phosphoric acid was dumped into self-contained ponds on the south bank of Tejo River, at the industrial area of Barreiro near Lisbon, for decades. Production and disposal of phosphogypsum was discontinued in the early 90’s due to changes in industry, and a contamination assessment was performed at that time. Since then large amounts of phosphogypsum have remained exposed to weathering while a decision on the management of this material was pending. The waste piles were re visited in 2016 and a survey of radioactivity distribution in the phosphogypsum and in the area was carried out. Determinations of radionuclide concentrations (238U, 235U, 234U, 230Th,226Ra, 210Pb, 210Po, 232Th) were performed by alpha spectrometry in samples of phosphogypsum, plants spontaneously grown on the waste piles and in surroundings, groundwater, and in atmospheric aerosols. Similar analyses were performed also in samples from a comparison site further away and in a similar environment. In general, radionuclide transfer from phosphogypsum to plants was minimal, although radium (226Ra) dissolution from phosphogypsum piles and its percolation into the groundwater was noticeable. Ambient radiation doses and radionuclide concentrations in the terrestrial environment around the piles and at the comparison site are compared, and showed reduced dispersal of radioactive elements in the terrestrial environment. Options for reuse of phosphogypsum and phosphogypsum confinement on site are discussed.
Key words: phosphate industry, radioactivity, waste management, environmental contamination.