An easy method for Ra-226 determination in river waters by liquid-scintillation counting

Ra-226 activity concentration in river water was determined using a low bac kground liquid scintillation counter. Radium was extracted from the samples as Ra-BaSO4 precipitate which, afterwards, was dissolved with EDTA in ammo nia medium. Solution was transferred into a low potassium glass vial and th en mixed with a scintillation cocktail. Two different scintillation cocktai ls were selected for comparison. Efficiency, recovery yield and odp separat ion were studied with both liquid scintillation cocktails. One single measu rement, made one month after radium separation, allows to calculate the Ra- 226 concentration as well as to assess the presence of alpha contamination of the sample. In the case of negligible interferences, Ra-224 concentratio ns can be subsequently evaluated in the same sample by the measurement made just after chemical separation of radium. This method has been applied for the determination of Ra-226 and Ra-224 activity concentrations in river wa ter collected from different locations along the Odiel river estuary area ( South-west of Spain). The presence of chemical industry, the wastes of whic h are released into the river, could be connected with radium activity conc entration enhancements in the water.