Present status of 222Rn in groundwater in Extremadura

Radon-222 was measured in groundwater sources of Extremadura (Spain), analyzing 350 samples from private and public springs, wells, and spas by liquid scintillation counting (LSC) and gamma spectrometry. The 222Rn activity concentrations ranged from 0.24 to 1168 Bq L−1. The statistical analysis showed a log-normal distribution with a mean of (111 ± 7) Bq L−1 and a median of (36 ± 3) Bq L−1. A hydrogeological study revealed correlations between the activity concentration and the aquifer material's characteristics. A map of 222Rn in groundwater was elaborated and compared with the natural gamma radiation map for this region. About 35% of the samples showed 222Rn activity concentrations above the Euratom recommended limit of 100 Bq L−1. Three uranium series radionuclides (238U, 234U, and 226Ra) were also assayed by alpha-particle spectrometry, estimating the annual effective dose due to the presence of these natural radionuclides in drinking water.