The detector used to determine the radon concentrations in
water samples is the RAD 7 portable monitor and its accessory RAD
H2O from Durridge.1 The radon detector consists on an electrodepositing
chamber and a semiconductor, allowing distinguishing
between 222Rn and 220Rn. The H2O accessory configures a closed air
circuit with the RAD 7, the water sample, and a bubbling device
used for radon degassing from water. After measurement we corrected
our results taking into account disintegration between
sampling and measuring.