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 background liquid scintillation counter. Radium was extracted from the samples as Ra-BaSO4 precipitate which, afterwards, was dissolved with EDTA in ammonia medium. Solution was transferred into a low potassium glass vial and then mixed with a scintillation cocktail. Two different scintillation cocktails were selected for comparison. Efficiency, recovery yield and odp separation were studied with both liquid scintillation cocktails. One single measurement, 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 concentrations 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 water collected from different locations along the Odiel river estuary area (South-west of Spain). The presence of chemical industry, the wastes of which are released into the river, could be connected with radium activity concentration enhancements in the water.