Studies of the radon concentration in drinking water from the horst Soderasen in Southern Sweden

The radon activity concentration in ground water from drilled and dug wells on the horst Soderasen in Southern Sweden has been determined with two dif ferent methods, gamma activity measurements with a germanium HPGe detector and alpha activity measurements with plastic track detectors. The results a re consistent. High activity concentration is connected to granite bedrock. Dug wells have low concentrations and no trivial correlation between conce ntration and depth of the well is found. Large local variations exist. Acti vity concentrations > 700 Bq/l appear to be associated with leakage from la yers of volcanic origin. The concentration from drilled wells is found to b e quite constant over a 3 year period but short time variations appear to b e significant. Evaporation from the open surface of a normal cooking vessel is slow with an activity gradient DeltaA/A of about 0.1-0.2 per hour at ro om temperature whereas even modest heating of water in e.g. a coffee machin e is very efficient and reduces the radon activity concentration by > 90% i n one process. (C) 2001 Elsevier Science Ltd All rights reserved.