Uranium pollution in an estuary affected by pyrite acid mine drainage and releases of naturally occurring radioactive materials

► Huelva estuary is affected by former phosphogypsum releases and pyrite acid mine drainage. ► Time evolution of uranium concentration is analyzed after halting of NORM releases. ► Two new contamination sources are preventing the complete uranium cleaning: (1) The leaching of phosphogypsum stacks located close to Tinto River. (2) Pyrite acid mine drainage. ► High uranium concentrations are dissolved in water and precipitate subsequently.