# A New Methodological Approach for the Assessment of the \({}^{238}\)U Content in Drinking Water
## 1 Introduction  
As is well known, the study of natural radioactivity, due to the presence of primordial radionuclides in the Earth's crust and to cosmogenics [1, 2], provides information on the radiological risk for the population and on the variations in background radiation due to nuclear activities, industries, power plants, etc. [3, 4]. In this context, environmental monitoring of natural radionuclides and their progeny has received considerable attention around the world [5, 6]. Although the environmental aspects of natural radioactivity have been discussed in numerous scientific publications [7, 8, 9, 10], the presence of natural radioisotopes in drinking water as a hazard factor for the public has not yet been addressed in sufficient detail [11, 12]. It is well known that water is very important for our life, since it constitutes from 50% to 60% of the weight of our body, playing an active role in all its vital processes [13]. For this reason, water must be free from pollutants that could pose a risk to human health [14]. Water quality assurance is therefore one of the most important issues in environmental programs to protect public health [15, 16]. The Italian Legislative Decree 28/2016 constitutes the current national legislative reference for the quality of water intended for human consumption as regards radioactivity. It regulates themodalities of control of radionuclides by means of indicator parameters [17]. Among the natural radioisotopes to be controlled, \({}^{238}\)U is certainly one of the most significant, given the predominant role assumed in the determination of the gross alpha activity concentration, and therefore of the total Indicative Dose (ID) [18].  
As a matter of fact, the concentration of uranium in water depends on many factors, including the type of rock of the host aquifer, the presence of oxygen and complexing agents, the chemicals present in the aquifer, the chemical reactions with the ions in solution and the natural contact between uranium ores and water [19]. For example, if the bedrock consists mainly of uranium-rich granitoids and granites and contains soft and slightly alkaline bicarbonate waters, uranium is highly soluble under oxidizing conditions over a wide pH range [20]. Generally, the uranium content of natural water can range from trace levels to 600 \(\mu\)g/L or more [21].  
This article reports a new methodological approach, developed in order to evaluate the \({}^{238}\)U content in a drinking water sample from Paola, Calabria region, southern Italy, taken as a case study. The evaluation was carried out through High Purity Germanium (HPGe) gamma-ray spectrometry measurements, with the aim of quantifying the specific activity of the natural radionuclide \({}^{234\mu}\)Pa after preconcentration and therefore of evaluating the activity concentration of \({}^{238}\)U, in secular radioactive equilibrium with its daughter. Generally, such a condition occurs when the half-life of the child radionuclide is much shorter than that of the parent radionuclide. In our case, as the half-life of \({}^{234\mu}\)Pa (child) and \({}^{238}\)U (parent) are equal to 69.5 s and 141 \(\times\)\(10^{15}\) s, respectively, their secular radioactive equilibrium can be reasonably hypothesized [22, 23]. Although the \({}^{238}\)U is a pure alpha-emitter radionuclide, the choice of using HPGe gamma spectrometry with respect to other alpha-based techniques, i.e., alpha spectrometry or liquid scintillation, is due to a more simplified overall analytical activity. The obtained results were then validated by a comparison with the concentration of \({}^{238}\)U (\(\mu\)g/L) determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) analysis.