Investigation of potential environmental radiation risks associated with artisanal gold mining in Zamfara State, Nigeria

A total number of 166 average measurements were taken using a handheld radiation meter. The mean terrestrial gamma radiation dose rate (TRD) was 32 nGy h(-1) which is less than the world average value of 59 nGy h(-1). Kaura Namoda has the highest TRD with a value of 38 nGy h(-1), while Bakura has the lowest TRD with a value of 28 nGy h(-1). The mean activity concentrations of Ra-226, Th-232 and (40) K in soil samples were measured using HPGe and were found to be 18 +/- 2 Bq kg(-1), 22 +/- 3 Bq kg(-1) and 251 +/- 7 Bq kg(-1), respectively. Highest activities of Ra-226, Th-232 and (40) K were all found to be in Zurmi local government area with respective values of 31 +/- 3 Bq kg(-1), 34 +/- 3 Bq kg(-1) and 419 +/- 10 Bq kg(-1). The radiological hazards indices associated with the measured activity concentrations were determined as 69 Bq kg(-1), 0.2, 0.24, 32 nGyh(-1) and 0.05 mSvy(-1) for radium equivalent (Ra-eq), external hazard index (H-ex), absorbed dose rate (D-R) and annual effective dose (AED), respectively. It can be concluded that despite the illegal mining activities within the area, the radiation exposure level in the area is normal and will not pose any immediate radiation effect to humans and their environs.