Groundwater radon level and soil radionuclide concentration have been measured in the volcanic region
of La Garrotxa (Catalonia, Spain) to further research on the origin and dynamics of high radon levels over
volcanic materials found in this region. Water samples from different aquifers have been collected from
wells and springs and the water radon levels obtained have been lower than 30 Bq l1. Soil samples have
been collected from different geological formations (volcanic and non-volcanic), being Quaternary
sedimentary deposits those that have presented the highest mean values of 40K, 226Ra and 232Th concentrations
(448 70 Bq kg1, 35 5 Bq kg1 and 38 5 Bq kg1, respectively). Additionally, indoor/
outdoor terrestrial radiation absorbed dose rate in air have been measured to better characterize the
region from the radiological point of view. Terrestrial radiation absorbed dose rates measurement points
have been chosen on the basis of geological and demographical considerations and the results obtained,
from 27 to 91 nGy h1, show a clear relation with geological formation materials. The highest terrestrial
gamma absorbed dose rate is observed over Quaternary sedimentary deposits as well. All these results
help to better understand previous surveys related with indoor and outdoor radon levels and to reinforce
the hypotheses of a radon transport through the fissure network.