Pollution evaluation on the salt-marshes under the phosphogypsum stacks of Huelva due to deep leachates.

ABSTRACT

In the salth-marshes of the Tinto River (Huelva estuary, SW Spain), are stored in stacks around 100 Mt of PG, covering a surface of 1000 ha without any type of isolation, which produce an important impact in the surrounding environment. On the other hand, this ecosystem it is affected by acid mine drainage (AMD) from sulphide mines located upstream the Tinto River. The aim of this study is to evaluate the deep pollution of the underlain salt-marsh sediments due to leachates from the PG stacks. For that purpose, 7 cores were collected from zones 2 and 3 of the stacks, and PG and salt-marsh sediments samples from different depths were analyzed. The physicochemical parameters, mineralogy, granulometry and the concentration of the main elements of interest were determined in the samples. Most analysed salt-marsh sediments are not affected by PG stacks pollution, because sediments act as a "barrier" for the leachates from the PG, concentrating the contaminants in the first decimetres (0.5 m) under PG-sediments contact, and the deep infiltration is very limited. The obtained results suggest that the perimeter channel which is projected to build in the restauration project, should has a depth of 1 m below the level of the PG stacks for assuring the complete collection of leachates from the stacks, and avoid their liberation into the Tinto River estuary.