Assessment of radiological health hazards from measured activity concentrations in soil samples around Gbose Quarry Omu-aran, Kwara State

Abstract

Activity levels of Naturally Occurring Radioactive Materials (NORM) from soil samples around Gbose quarry of Omu-aran, Kwara State, Nigeria, was determined by using gamma ray spectrometry technique. The gamma radiation levels were measured by integral counting using a gamma spectrometer which consists of a scintillation detector NaI(Tl) of ( 2''x 2'') crystal dimension with resolution value of 6.48% for line energy of 662 keV. Soil samples were randomly collected around the study area. The radiological effects on human due to the natural radiations from sand were also estimated by use of radiological parameters. The measured mean activity concentration levels of 238U, 232Th and 40K were found to be 94.93 Bqkg^-1 , 88.40 Bqkg^-1 and 1763.79 Bqkg^-1 respectively. These levels were found to be higher than the worldwide accepted average values of 30, 35 and 400 Bqkg^-1 for ²³⁸U, ²³²Th and ⁴⁰K respectively. The mean absorbed dose rate was 172.31nGyh^-1 while the mean annual effective doses were 0.85 mSv/yr and 0.21 mSv/yr for indoor and outdoor respectively. The annual effective doses obtained in the study although are lower than the 1 mSv/yr threshold as set by the International Commission on Radiological Protection (ICRP) for members of the public, however the mean absorbed dose of 172.31nGyh^-1 is about 300% of the world average of 60nGyh^-1 as set (United Nation Scientific Committee on the Effects of Atomic Radiation, UNSCEAR, 2008). Consequently, adequate caution must be taken in the use of the soil within the study area for building as it may pose future radiological hazard.