Application of a mathematical model to an artificial aquifer under different recharge/discharge conditions using 222Rn as a tracer

Radon (Rn-222), a radioactive gas of natural origin, was listed by the World Health Organization in 2009 as the second largest cause of lung cancer (3-14%) after tobacco. Global awareness of the importance of controlling its concentration in water led to the implementation of the European Directive 2013/51/Euratom, which establishes permitted levels in drinking water. This study applies a mathematical model to determine Rn-222 concentration in water supplying an artificial aquifer over the full range of recharge/discharge conditions (volumes and times, and therefore flows). This was done by creating an artificial aquifer on a laboratory scale, which reproduces the recharges and discharges experienced by real aquifers through rainwater or groundwater. The equipment used in this study was an RTM 2100 with a specific system for continuous monitoring of Rn-222 in water, a high-purity Ge detector for gamma spectrometry, and a portable liquid scintillation counter (LSC) called Triathler for specific measurements of Rn-222 in water. The aim of this paper is to show the application of the mathematical model under different recharge/discharge conditions applied to the artificial aquifer. The concentration of Rn-222 in water determined by the model can also be used as a tracer to find the origin and volume of water that reaches a real aquifer.