Gamma Radioactivity levels of Rocks and Soils and Their Corresponding External Exposure in Navy Quarry Site, Abeokuta, South-West, Nigeria

Okedeyi, A.S ; Arowolo, T.A ; Gbadebo, A.M ; Techokosa, P (2012)

Asian Journal of Applied Science

Journal

Crystalline rocks have been observed to be rich in Naturally Occurring Radionuclides (NOR) which are the primary terrestrial sources of radiation in the environment. This study determined the activity concentrations of NOR in rocks and soils from Saunder quarry site, Abeokuta North, South-Western, Nigeria. Three rocks were randomly collected and ten soil samples comprising five surface and five sub-surface were collected by pitting to depth of interest in each location and analyzed using Nal (Tl) gamma spectrometer. The average activity concentrations of 4QK, 238U and 232Th in rock samples were 603.62±83.29, 39.70±12.57 and 62.64±20.71 Bq kg -1, respectively. The calculated average Absorbed Dose Rate (ADR) and Annual Effective Dose (AED) were 84.01 nGy h _l and 103.03 jiSv y _l. While for soils, the mean activity concentration for the two depths were 145.10*12.64 and 236.08±17.34 Bqkg -1 for 40K, 13.36±3.53 and 23.99±6.80 Bqkg -1 for 238U and 15.09±5.48 and 10.54±5.67 Bqkg -1 for 232Th, respectively. Similarly, the corresponding average ADR and AED for soil were 28.99 nGy h -1 and 35.56 jiSv y -1 for surface 33.32 nGy h -1 and 40.87 jiSv y -1 for sub-surface, respectively. The average values for AED of the sampled rock were higher than 70 jiSv y _l. Hence, the granite rock used for building and construction purpose from the study area would be rich in NOR. Routine assessment of radionuclide contents of the rocks of the quarry site was recommended