Radioactive characterization of leachates and efflorescences in the neighbouring areas of a phosphogypsum disposal site as a preliminary step before its restoration

Abstract

After the recent closure of certain phosphoric acid plants located in the South-West of Spain, it has been decided to restore a big extension (more than six hundred hectares) of salt-marshes, where some million tonnes of phosphogypsum (PG), the main by-product generated by these plants, had been disposed of. This PG is characterized by its content of high activity concentrations of several radionuclides from the uranium series, mainly ²²⁶Ra, ²¹⁰Pb, and ²¹⁰Po and, to a lesser extent, U-isotopes.

The PG disposal area can be considered as a potential source of radionuclides into their nearby environment, through the waters which percolate from them and through the efflorescences formed in their surroundings. For this reason, a detailed radioactive characterization of the mentioned waters and efflorescences has been considered essential for a proper planning of the restoration tasks to be applied in the near future in the zone. To this end, U-isotopes, ²³⁴Th, ²³⁰Th, ²²⁶Ra, ²¹⁰Pb and ²¹⁰Po activity concentrations have been determined by applying both alpha-particle and gamma-ray spectrometric techniques to selected water and efflorescence aliquots collected in the area.

The analysis of the obtained results has enabled to obtain information about the geochemical behaviour in the area of the different radionuclides analyzed; and the conclusion to be drawn that, in the restoration plan under preparation, both the prohibition of outflowing waters from the disposal area to the neighbouring salt-marshes, and the removal of all the efflorescences now disseminated in their surroundings are essential.