Behaviour of heavy metals and natural radionuclides in the mixing of phosphogypsum leachates with seawater

Phosphogypsum (PG) is disposed worldwide in large stacks usually placed coastal zones, as the case of Huelva (SW Spain), where around 100 Mt PG are stored on salt marshes Tinto River estuary covering a surface about 1000 ha. This management generates weathering PG, and due to its high acidity (pH ≈ 2) pollutant load can provoke significant emissions into their surroundings. In this work were evaluated by laboratory experiments effects pH increase behaviour heavy metals natural radionuclides during mixing phosphogypsum leachates with seawater. The acidic showed concentrations from two three orders magnitude higher than continental waters, (U-isotopes 210Po) four five unperturbed aquatic systems. Major elements some Mn, Ni, Cd, As, Sb Co conservative neutralisation seawater, remaining liquid phase, while other ones Al, Fe, Cr, Zn, Cu, Pb precipitated and/or adsorbed onto solid phase. U-isotopes 210Po clear non-conservative probably coprecipitation/adsorption processes formed precipitates, but reached total removal at 7, U- isotopes after 5 returned phase redissolution/desorption near neutral pH. mainly composed iron phosphates particles, metal radionuclide one soils. All these facts demonstrate serious environmental impact produced surroundings urgency effective restoration measures.