Biology / Medicine
March 22, 2017
concentration, gamma dose, effective dose, radium equivalent and hazard index
The activity concentrations of natural gamma-emitting radionuclides 238U, 232Th and 40K in soils from some Local Government Areas (LGAs) in Lagos State Nigeria have been measured by using a well calibrated high resolution gamma ray spectrometer. The LGAs were grouped under Lagos Mainland and Lagos Island. The mean activity concentration values of 23.22, 25.72 and 164.03 Bq kg-1for 238U, 232Th and 40K respectively were obtained for the LGAs. Ikorodu was found to have the highest gamma dose rate (84.46 nGy) and the least gamma dose was obtained in Surulere. The consequent annual effective dose of the two LGAs were 1.037 and 0.076 μSv y-1 respectively. The highest value of radium equivalent, Raeq across the surveyed LGAs was 144 Bq kg-1. This value was far below the permissible limit of 370 Bq kg-1given by UNSCEAR 2000 for soil that contains 238U, 232Th and 40K. The values obtained for both internal and external hazard indexes (Hin and Hex) varied from 0.033 to 0.629 Bq kg-1. These shows that the radiation hazards are negligible since all the values are less than unity. The values obtained for most of the parameters considered were higher for Mainland as compared with the Island of the city under survey.