Speaker
Prof.
Ioannis Pashalidis
(Department of Chemistry, University of Cyprus)
Description
The present study aims to assess the effect of redox conditions existing within a phosphogypsum disposal site on the redox stability and mobility of uranium in the disposed material. Phosphogypsum sampling and in-situ measurements were carried out at a coastal stack in Vasiliko, Cyprus. pH, EH and solubility experiments were performed in-situ and in laboratory systems. Generally, in the open stack oxidizing conditions predominate stabilizing uranium in its hexavalent oxidation state. On the other hand, after the application of a soil/vegetative cover and in the presence of natural organic matter, anoxic conditions prevail (EH < -70 mV) enabling U(VI) reduction to U(IV). Uranium concentration measurements as well as 230Th/238U ratios show higher uranium retention under anoxic conditions, which could be ascribed to the lower solubility and mobility of U(IV).
Primary author
Prof.
Ioannis Pashalidis
(Department of Chemistry, University of Cyprus)
Co-author
Juhani Suksi
(Laboratory of Radiochemistry, Department of Chemistry, University of Helsinki (Fi))
