The purpose of this study was to determine the activity concentrations of uranium isotopes (234 U and 238 U) and the 234 U/ 238 U activity ratios in groundwater wells from Saudi Arabia. These wells are located in two different regions and tapping different aquifers. The uranium isotopes were measured by alpha spectrometry. The uranium activity ratios (234 U/ 238 U) in the investigated samples had an average value of 1.38 and ranged from 1.0 to 2.17. The relationship between the activity concentrations of the combined uranium and the water chemical composition in the studied wells was also investigated. Good correlation was found with redox potential described by R 2 value of 0.74. Also, a good negative correlation was observed between The TDS content of the groundwater samples and the uranium activities described by R 2 value of 0.59. Finally, with twenty groundwater samples collected from two large areas, the presence of uranium isotopes in the Saq and Dammam aquifers can't be easy to judge but within the framework of this study, it can be concluded that the distribution of 238 U and 234 U in these two aquifers is more dependent on the mineralogical composition of the aquifer matrix and by the geochemical/hydrochemical conditions present.
The natural radioactivity levels in groundwater, soil and crops have been determined in seven farms at Hail region in Saudi Arabia to assess any radiological hazards to the public, and to maintain a radiological map of natural radioactivity levels in this region. The radium isotopes (226 Ra and 228 Ra) were measured in groundwater samples collected from wells in these farms, and the 228 Ra activity concentrations exceeded the national guidance level of 2.7 pCi/L set by Saudi Arabian Standards Organization (SASO) and the WHO. These relatively higher activities did not contribute to the annual effective dose rate from the ingestion of both isotopes (226 Ra and 228 Ra) in the analyzed crops, which showed lower values than the upper limit of 1 mSv/yr. The activity concentrations of 228 Ra in soils of five farms were found to be higher than the world average value reported by the (United Nations Scientific Committee on the Effects of Atomic Radiation) UNSCEAR. These relatively higher activities contributed to the absorbed dose rate in air from external gamma radiation which was higher than the world average value of 57 nGy/hr in some farms. These high activities contributed also to the annual effective dose which showed values higher than the world average value of 0.07 mSv/yr for outdoor terrestrial gamma radiation in three farms. On the basis of these results, it can be concluded that the presence of such activities in the groundwater and crops samples do not pose any radiological hazards or significant risk to the public and animals, since they drink these waters. it may be recommended that the activity levels of the combined radium isotopes in the animal products (milk and meat) and the annual effective dose should be estimated to evaluate the contribution of the 228 Ra exceeded limits in these wells.
In this study, the total uranium concentration was determined in groundwater samples used for irrigation and/or drinking purposes and collected from private wells in Al Sharqiya region, Saudi Arabia. The uranium concentrations were measured by laser fluorimetry preceded by radiochemical treatment to eliminate the quenching effect due to the high total dissolved solids content in the groundwater samples. For method validation, some of the measured samples were analyzed for uranium isotopic activities and measured by alpha spectrometry. The results of the uranium concentrations obtained by laser fluorimetry and alpha spectrometry were in good agreement. The uranium concentrations in all the samples were below the World Health Organization (WHO) recommended limit of 30 μg L. Two different approaches were followed to assess the annual effective dose from the ingestion of uranium in the analyzed groundwater samples. The annual effective doses determined by the two approaches were found to be in agreement, and varied from 2.9 to 10.2 μSv y, with a mean value of 6.1 μSv y, which is far below the WHO recommended level of 100 μSv/y. The modified laser fluorimetric procedure was found to be a good tool compared with other techniques for direct measurement of uranium concentrations in high total dissolved solids groundwater samples at low levels.
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