Evaluation of radiological hazards in the sediments of Ogun river, South-Western Nigeria

The concentrations of natural radionuclides in the sediments of Ogun river in South Western Nigeria have been measured and determined using gamma-ray spectrometry. The mean activity concentrations of (40)K, (226)Ra, and (232)Th at different locations along the course of the river were found to vary from 370.99 +/- 19.26 Bq/kg (at Olopade) to 608.02 +/- 24.66 Bq/kg (at Owere), 5.57 +/- 2.34 (at Ekerin) to 20.40 +/- 4.52 Bq/kg (at Sokori) and 5.04 +/- 2.24 Bq/kg (at mile 12-Maidan) to 23.10 +/- 4.81 Bq/kg (at Sokori) respectively. The overall calculated mean of the total indoor absorbed dose rates was 64.46 +/- 9.16 nGy/h with corresponding annual indoor effective dose of 0.32 +/- 0.05 mSv/y. Radium equivalent activity (Ra(eq)), external hazard index (H(ex)), internal hazard index (H(in)) and representative gamma index (I(gamma r)) were calculated in order to assess the radiation hazards associated with the use of these sediments in the construction of dwellings. The overall estimated values for the radium equivalent activity, external hazard index, internal hazard index and the representative gamma index were 67.96 +/- 10.74 Bq/kg, 0.18 +/- 0.03, 0.22 +/- 0.05 and 0.54 +/- 0.08, respectively. These values obtained for the river sediments were less than the recommended safe and criterion limits by UNSCEAR and also, they compared well with the values from other countries of normal radiation areas. It suffices to say therefore that sediments from Ogun river are safe and can be used for construction of buildings without undue radiological health concerns. Results of the study could serve as an important baseline radiometric data for future epidemiological studies and monitoring initiatives in the study area. (C) 2011 Elsevier Ltd. All rights reserved.