title: An assessment of natural radioactivity of soils and its external radiological impact in southwestern Nigeria.
abstract: Soil samples collected from five states in the southwestern part of Nigeria have been analyzed for activity concentration of gamma-ray emitters. The States were Oyo, Lagos, Ondo, Ogun, and Osun. Activity concentration measurement was carried out using a co-axial type high purity germanium (HPGe) detector. Spectral analyses were performed using spectrometry software. The activity concentration measured ranged from 0.03 +/- 0.2 Bq kg(-1) for 137Cs to 1,358.6 +/- 28.5 Bq kg(-1) for (40)K. (40)K accounted for most of the activity. The calculated absorbed dose rates in air at 1.0 m above the ground ranged from 6 to 303 nGy h(-1) with a mean and standard deviation of 60.5 nGy h(-1) and 63.2 nGy h(-1), respectively. Estimated annual outdoor effective dose equivalent varied from 8 to 370 mSv y(-1). The calculated collective dose equivalent values for the five states ranged from 87,000 person-Sv to 600,000 person-Sv. The estimated annual outdoor effective values were considerably higher than the world soil average value of 70 microSv y(-1) reported by the International Commission on Radiological Protection.
authors.affiliation: Department of Physics, Federal University of Technology, Akure, Ondo State, Nigeria. ajayisam1089@yahoo.com
authors.forename: O S
authors.initials: OS
authors.lastname: Ajayi
authors.forename: S B
authors.initials: SB
authors.lastname: Ibikunle
authors.forename: T J
authors.initials: TJ
authors.lastname: Ojo
mesh_terms: D000042:Absorption; D000396:Air Pollutants, Radioactive / Q000032:analysis; D000531:Altitude; D001417:Background Radiation; D006801:Humans; D009549:Nigeria; D011156:Population Density; D011851:Radioactivity; D011868:Radioisotopes / Q000032:analysis; D012987:Soil / Q000032:analysis*; D012990:Soil Pollutants, Radioactive / Q000032:analysis; D013051:Spectrometry, Gamma
chemical_list: D000396:Air Pollutants, Radioactive; D011868:Radioisotopes; D012987:Soil; D012990:Soil Pollutants, Radioactive