Distribution of Natural Radionuclides, Rare Earth Elements, Metals and Metalloids in a Phosphogypsum Stockpile.

M. José Madruga; M. Isabel Prudêncio; José Alberto Gil Corisco; Rosa marques; Mários reis; Maria Isabel Flausino de Paiva; Maria Isabel Dias

Key information

Authors:

M. José Madruga (Maria José Bação Madruga); M. Isabel Prudêncio (Maria Isabel Garrido Prudêncio); José Alberto Gil Corisco (José Alberto Gil Corisco); Rosa marques (Rosa Maria Salgueiro Marques); Mários reis (Mário João Capucho dos Reis); Maria Isabel Flausino de Paiva (Maria Isabel Flausino de Paiva); Maria Isabel Dias (Maria Isabel Marques Dias)

Published in

03/14/2019

Abstract

A first detailed study of phosphogypsum (PG) from a stockpile in Barreiro (Portugal) was performed aiming for a better characterization of this industrial waste deposit, considering its enhanced content in natural radionuclides and toxic metals, making it a potential contamination source to the Tejo estuary. Whole samples and aggregates of these wastes resulting from phosphate industries were analysed by neutron activation, gamma-spectrometry, X-ray diffraction and scanning electron microscopy. This work clearly shows that a significant chemical heterogeneity in the PG occurs due to the existence of aggregates with different compositions randomly distributed. Among these aggregates, the dark grey ones have high concentrations of Sc, Cr, Zn, Ga, Ba, REE, Ta, W, Th and U and the highest concentrations of 226Ra and 210Pb. The separation of these dark aggregates prior to any application of the PG would lead to a safer reuse of these wastes. The chemical patterns, including the REE distribution with a significant negative Ce anomaly, found in PG, are certainly related with the geochemical signatures of the phosphate rocks used as raw material. This PG stockpile may play a significant role as a radioactive source in the Tejo estuarine environment.