Radioactivity in the groundwater of a high background radiation area

Natural radioactivity was measured in groundwater samples collected from 37 wells scattered in an inhabited area of high natural background radiation, in a purpose of radiation protection. The study area is adjacent to Aja heights of granitic composition in Hail province, Saudi Arabia. Initial screening for gross α and gross β activities showed levels exceeded the national regulation limits set out for gross α and gross β activities in drinking water. The gross α activity ranged from 0.17 to 5.41 Bq L−1 with an average value of 2.15 Bq L−1, whereas gross β activity ranged from 0.48 to 5.16 Bq L−1, with an average value of 2.60 Bq L−1. The detail analyses indicated that the groundwater of this province is contaminated with uranium and radium (226Ra and 228Ra). The average activity concentrations of 238U, 234U, 226Ra and 228Ra were 0.40, 0.77, 0.29 and 0.46 Bq L−1, respectively. The higher uranium content was found in the samples of granitic aquifers, whereas the higher radium content was found in the samples of sandstone aquifers. Based on the obtained results, mechanism of leaching of the predominant radionuclides has been discussed in detail.