-In recent years, a decontamination project has been under way to remove the polluted sludge on the riverbed of the Ebro river, particularly in the area of Flix (Tarragona, Spain). This project started in 2011 and consists of the removal of the sludge and its treatment in a process that will eventually restore the river to its natural conditions. The sludge is a product of the historical dumping of contaminants by a chemical complex situated next to the river, and it contains a range of contaminants, such as heavy metals, semi-and volatile organic compounds, and radionuclides. Downstream of the complex, in the town of L'Ampolla, a drinking water treatment plant (DWTP) is located. This plant collects the water from the Ebro river and, after potabilisation, the plant supplies drinking water to the population of southern Catalonia. Due to the possible presence of radionuclides in the river water, it was considered important to monitor and control the radioactivity parameters regulated under current legislation for water consumption. For this reason, in this study, our aim is to evaluate if the decontamination work carried out in Flix has any effects on the radioactivity levels of both Ebro river and treated water, by means of the determination of gross alpha activity, gross beta activity and a group of gamma emitter radionuclides at three different sampling points in the period between 2008 and 2012. One sampling point was located a few kilometres from the Flix area and the other two were located before and after the DWTP, respectively. From the results obtained, it could be observed that no significant differences were obtained between the samples taken before and after the beginning of the decontamination process began, so it is important to highlight that this project has not affected the quality of the water supplied by the DWTP.

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