Radioelement (U, Th, Rn) concentrations in Norwegian bedrock groundwaters

Twenty-eight samples of groundwater from bedrock boreholes in three distinct Norwegian geological provinces have been taken and analyzed for content of Rn, U, and Th, together with a wide variety of minor and major species. Median values of 290 Bq/l, 7.6 mu g/l, and 0.02 mu g/l were obtained for Rn, U, and Th respectively, while maximum values were 8500 Bq/l, 170 mu g/l, and 2.2 mu g/l. Commonly suggested drinking water limits range from 8 to 1000 Bq/l for radon and 14 to 160 mu g/l for uranium. Radioelement content was closely related to lithology, the lowest concentrations being derived from the largely Caledonian rocks of the Trondelag area, and the highest from the Precambrian Iddefjord Granite of southeast Norway (11 boreholes) where median values of 2500 Bq/l, 15 mu g/l and 0.38 mu g/l, respectively, were obtained. The Iddefjord Granite is not believed to be unique in Norway in yielding high dissolved radionuclide contents in groundwaters, and several other granitic aquifers warrant further investigation in this respect.