Setting up a continuous monitor for the control of temporal variability of ^222Rn in groundwater: Application to samples from Tadla Basin, Morocco

Owing to its short period (t1/2= 3.8 d), the development of a technique allowing theanalysis of the radon with very low content was a challenge. In this paper we shalldescribe a robust method and portable technique (RAD7) for measuring moderate levelsof 222Rn in various matrices: soil, air, coastal water, river water and groundwater. Bypurging air through the sample, radon is emanated until a chemical equilibration isobtained between the two phases. The radon in the air loop is determined using theradon-in-air monitor. Since the distribution of radon at equilibrium between the air andwater phases is governed by a well-known temperature and humidity dependence, tocheck that, several tests were performed in the laboratory. This technique is used for thefirst time in Morocco for monitoring radon in the atmosphere and spatial distribution innatural waters, to establish a database on radon activity and for a radiologicalsurveillance either for hydrological applications. The obtained results showed that thesensitivity varies inversely proportional to the moisture in the measuring chamber. Alsothe water temperature dependence of the concentration of radon has been clearly shown.The atmospheric radon activity inside the laboratory was 0.326 ± 0.058 pCi/L.