Revisiting methods for the assessment of naturally-occurring radioactivity in drinking water

A comprehensive radioactivity characterisation of Castilla y León (Spain) groundwater intakes intended for human consumption is addressed between 2017 and 2021. This study responds to the radiological requirements stated in the European Council Directive 51/2013/EURATOM concerning drinking water for public health. Given that the gross α- and gross β-activity determination is used as a screening strategy for water radioactivity monitoring, the reliability of the thin-source deposit method (ISO 10704, 2019) has been improved to achieve representative values of the total activity coming from α- and β-particle emitters in the samples. More than 400 groundwater samples have been considered for this purpose, analysing their ^238,235,234U, ^228,226Ra, ²¹⁰Pb, and ²¹⁰Po activity concentrations, which are needed for the indicative dose assessment. These results, considered reference activity values, are compared with the gross α- and gross β-activities determined by the different procedure approaches. Ultimately, the results of the liquid scintillation counting method (ISO 11704, 2018) are also used to validate the optimised method.