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Accumulation and Leaching Zones of Uranium Specification by Radionuclides Mobility in Al-Madinah Al-Munawarah Soils Following Intense Rainfall Events |
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PP: 87-97 |
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doi:10.18576/jrna/110111
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Author(s) |
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Zainab Z. Alfull,
Mahmoud R. Khatab,
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Abstract |
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| Al-Madinah is located in the western province of the Kingdom of Saudi Arabia, approximately 150 km east of the Red Sea and around 400 km north of Makkah, encircled by mountains composed of volcanic and magnetic plutonic rocks. Soil samples gathered from the vicinity of Al-Madinah Al-Munawarah were analyzed radiometrically utilizing an HPGe detector. The activity concentrations of 238U ranged from 9.6±0.1 to 15.4±0.6 Bq.kg-1, while 232Th varied between 6.3±0.5 and 7.9±0.4 Bq.kg-1, 226Ra was found between 6.2±0.6 and 8.3±0.4 Bq.kg-1, and 40K levels ranged from 169.3±2.3 to 343.5±1.8 Bq.kg-1. The radionuclide concentrations in the examined soil are below international thresholds, indicating that their application is safe. Our findings revealed that the Th/U ratio in the soils and bottom sediments is less than 3.5, indicating uranium enrichment. The ratios of 234U/238U and 230Th/238U suggested that the majority of soil samples were situated within the accumulation zone, except for two samples found in the restricted zone, indicating turbid conditions. The 234U/238U activity ratio in most soil samples exceeded unity, ranging from 1.22±0.09 to 1.83±0.15, with one sample showing a value below 1; specifically, 0.93±0.06, which indicates relatively recent uranium uptake and preferential accumulation of 234U due to prevailing reducing conditions; that is, less than 1 million years from fluids that transported excess 234U from nearby rocks. The variation in the 230Th/234U activity ratio may be attributed to differences in the chemical characteristics of uranium and thorium, along with α-decay enhanced dissolution, re-adsorption, and re-precipitation of 234U. All calculated environmental hazard parameters for the soil samples fall within the range of international standards, affirming their safe use. The cluster analysis indicates that the primary environmental health hazard parameters arise from the activity concentrations of 238U and 226Ra. |
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