Radioecological study of an estuarine system located in the south of Spain

A big fertilizer industrial complex and a vast extension of phosphogypsum p iles (12 km(2)), sited in the estuary formed by the Odiel and Tinto river m ouths (south-west of Spain), are producing an unambiguous radioactive impac t in their sourrounding aquatic environment, through radionuclides from the U-series. The levels and distribution of radionuclides in the different wa ter phases of this estuarine system (filtered and particulate fractions) ha ve been determined. The analyses of radionuclide concentrations and activit y ratios have provided us with interesting information with which to evalua te the extension, degree and routes of the radioactive impact, as well with the knowledge of the different pathways followed for the radioactive conta mination which disturbs this natural system. The obtained results indicate that the main pathway of radioactive contamination of the estuary is throug h the dissolution in its waters of the radionuclides released by the indust rial activities and their later fixation on the particulate materials. On t he other hand, the tidal activity plays an important role in the transport and homogeneization along the estuary of the radioactivity released from th e fertilizer plants. Additionally, the results obtained for the different s tudied natural radionuclides (U-isotopes, Th-isotopes and Po-210) in the fi ltered and particulate fractions have provided very rich information about their different environmental behaviour in this aquatic system. (C) 2000 Pu blished by Elsevier Science Ltd. All rights reserved.