ABSTRACT

This study is undertaken to measure the variation of terrestrial gamma radiation and the

activity concentrations of U-238, Th-232 and K-40 in soil of Northern part of Zamfara State (Nigeria), and assess the potential health hazards associated with the exposures to the natural radiation in the area with respect to geological formations. Inspector AlertTM Nuclear Radiation Monitor and HPGe gamma ray spectrometer were used for TGRD and laboratory analyses respectively. The measured TGRD rates ranged from 20.00 to 61.43 nGy/h, with mean value of 31.99 nGy/h. The mean (range) activity concentrations of U-238, Th-232 and K-40 in the soil samples were 19.43 ± 2.23 (8.82 ± 0.95 to 44.22 ± 5.78) Bq/kg, 23.26 ± 8.43 (11.02 ± 1.03 to 43.96 ± 2.15) Bq/kg and 268.62 ± 39.03 (57.45 ± 2.88 to 527.36 ± 12.38) Bq/kg respectively. These results were compared with the world average values for specific activities (i.e. 33, 45 and 420 Bq/kg) for U-238, Th-232 and K-40 respectively, and were found to be less than the worldwide average. The highest TGRD rate and activity concentrations of U-238, Th-232 and K-40 were recorded in an area underlain by Older Granite formation, which are enriched with high contents of radioactive materials. The radiological hazards to the public in the studied area was assessed by estimating mean values of radium equivalent activity, external hazard index, and activity utilization index for the soil samples were found to be 71.674± 7.099 Bq/kg, 0.1936± 0.0192, and 0.4688± 0.0448 respectively.In addition, the mean values of absorbed gamma dose rates, annual outdoors effective dose rates, and excess lifetime cancer risk for both TGRD rate measurements and spectrometric analyses were found to be 31.99 nGy/h, 0.0393 mSv/y and 137.6x10-6, and 33.467

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