keywords: In-situ gamma-ray, survey meter, radiological assessment, soil samples, Nigeria
Olabisi Onabanjo University situated on basement complex has witnessed excavation of ground for purpose building constructions in the recent past. The excavation of ground and the use of building materials in constructions may enhance the level of natural ionizing radiation exposure of the environment. The study, therefore, aims at measuring the radioactivity levels in the environment of the University. Thirty grids were randomly mapped out in the campus and soil samples were collected from 4 or 5 points in each grid and mixed to form a representative sample. The activity concentrations of the soil samples were measured using a NaI(Tl) detector and the outdoor and indoor in-situ gamma survey was carried out using a Mirion RDS-30 survey meter. The mean radioactivity levels of the soils were 393.1±63.1 Bqkg-1; 17.6±3.0 Bqkg-1 and 12.5±1.7 Bqkg-1 for 40K, 238U and 232Th, respectively. The mean absorbed dose rate was 32.1±3.6 nGyh-1and the mean outdoor effective dose rate was 39.3±4.4 μSvy-1. The mean outdoor in-situ effective dose rate was 124.8±64.3 μSvy-1 and the highest mean indoor in-situ effective dose rate of 271.8±32.8 μSvy-1 was measured at the University Health Centre. The gamma and effective dose rates measured in the soils from the study area are lower than the world average values 50 nGyh-1 and 70 μSvy-1, respectively. The high values of indoor in-situ effective dose rate compare to outdoor in-situ effective dose may be attributed to the radiation emission from the materials used for the construction of buildings with cramped offices without cross ventilations.