Assessment of radionuclide and metal contamination in a thorium rich area in Norway
Abstract
The Fen Central Complex in southern Norway, a geologically well investigated area of magmatic carbonatite rocks, is assumed to be among the world largest natural reservoirs of thorium (232Th). These rocks, also rich in iron (Fe), niobium (Nb), uranium (238U) and rare earth elements (REE), were mined in several past centuries. Waste locations, giving rise to enhanced levels of both radionuclides and metals, are now situated in the area. Estimation of radionuclide and metal contamination of the environment and radiological risk assessment were done in this study. The average outdoor gamma dose rate measured in Fen, 2.71 μGy h−1, was significantly higher than the world average dose rate of 0.059 μGy h−1. The annual exposure dose from terrestrial gamma radiation, related to outdoor occupancy, was in the range 0.18–9.82 mSv. The total activity concentrations of 232Th and 238U in soil ranged from 69 to 6581 and from 49 to 130 Bq kg−1, respectively. Enhanced concentrations were also identified for metals, arsenic (As), lead (Pb), chromium (Cr) and zinc (Zn), in the vicinity of former mining sites. Both radionuclide and heavy metal concentrations suggested