Time Evolution of Activity Concentration ofNatural Emitters in a Scenario Affected ByPrevious Phosphogypsum Contamination

摘要

The estuary formed by the confluence of Tinto and Odiel river-mouths is located in theSouth of Spain, close to Huelva town. This estuary has been deeply studied through the yearsbecause it has a double particularity. On one hand, since the beginning of the 1960s, the estuaryhas been affected by direct and indirect phosphogypsum (pg.) releases from two phosphoric acidand fertilizers factories that are working in the area. On the other hand, the pyrite miningoperations upstream the Odiel and Tinto rivers has caused historically the formation of H2SO4,through oxidation of the natural sulphur deposits, the acidification of the waters and theconsequent mobilisation of heavy metals from the mining area to the Huelva estuary. As aconsequence, enhancement contamination levels in natural emitters from the ~(238)Useries werefound in the surroundings of the factories in the previous years to 1998. However, in 1998 themanagement policy of waste releases drastically changed in the area, and direct discharges toTinto and Odiel River had to be ceased.A thorough study of the affected zone is being carried out. Riverbed sediments and water sampleshave been analyzed from four different sampling campaigns in the estuary during the years 1999,2001, 2002 and 2005. Different radioanalytical techniques have been employed to obtain theactivity concentrations of U-isotopes, Th-isotopes, ~(226)Ra,~(210)Pband ~(210)Po.Furthermore, the resultsfor the rates of de-contamination of the area are presented. This data will be discussed in order toestablish the present status of the contamination in the area, and moreover, to predict the time-evolution of the self-cleaning