Abstract
The existence of a very high extension (about 1000 ha) of phosphogypsum piles, sited in the estuary formed by the mouths of the Tinto and Odiel rivers (SW Spain), produce a quite local, but unambiguous radioactive impact in the surrounding salt-marshes. In these piles the main by-product formed in the manufacture of phosphoric acid is stored. The radioactive impact is generated by the deposition and accumulation of radionuclides from the uranium series that previously had been mainly leached or dissolved from the piles by waters that temporally can cover or cross them. Other means of impact, especially through the atmosphere, have been evaluated as negligible or not detectable.