Assessment of radioactivity contents in bedrock groundwater samples from the northern region of Saudi Arabia

Recognizing the vast uses of water in human life, the presence of alpha and beta particles emitting radionuclides in groundwater of northern Saudi Arabia has been evaluated as a means of water quality assessment of the region. A liquid scintillation counting technique was used to determine the gross alpha/beta, and Ra-228 radioactivities in water samples, while the radioactivity concentrations of U-234,U-238 and Ra-226 were determined using alpha spectrometry after the separation process. Present results show that all water samples contain a higher level of gross alpha and beta radioactivity than the WHO recommended limits; the average gross alpha activity is about 7 times greater than the limit value of 0.5 Bq L-1, while the average gross beta activity value is about 3.5 times greater than the limit value of 1 Bq L-1. Correlations of TDS and pH with gross alpha and beta radioactivity in the studied samples were investigated. The activity ratio of the measured U and Ra alpha emitters to the gross alpha radioactivity and the ratio of the measured beta emitters to gross beta radioactivity were also discussed. Furthermore, interesting information on thorium abundance and radioactive disequilibrium in U series were observed by studying the activity ratio of Ra-228/Ra-226, Ra-226 /U-238, and U-234/U-238. Although these samples are not directly used for human being drinking, and mainly used in irrigation, the higher gross alpha/beta radioactivity may cause health risks to humans, since these radionuclides may enter the food chain through irrigation water. Thus, further radioactive risk assessment is highly recommended. (C) 2019 Elsevier Ltd. All rights reserved.