Abstract
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 alpha and gross beta activities showed levels exceeded the national regulation limits set out for gross alpha and gross beta activities in drinking water. The gross alpha activity ranged from 0.17 to 5.41 Bq L-1 with an average value of 2.15 Bq L-1, whereas gross beta 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 (Ra-228 and Ra-228). The average activity concentrations of U-238, (234)u, Ra-226 and Ra-228 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. (C) 2014 Elsevier Ltd. All rights reserved.