keywords: Marble, radionuclides, radiation, effective dose, hazards
The natural radioactivity levels of some marble deposits in parts of Nigeria were carried out to evaluate possible radiological hazard associated with them. This will help to assess the possible radiological risks to human health. The collected samples were pulverised, dried at 1100C in order to remove moisture, and sealed in plastic beakers and kept for about four weeks for equilibrium to be reached between 226Ra and its progeny 214Pb. The natural radioactivities of the collected marble samples were measured using the gamma spectrometer which contains a NaI (Tl) detector connected to Multichannel Analyser (MCA). Results of measured ƴ-ray spectra and activity concentrations of the marble samples are; 232Th (9.72+ 4.02 – 25.83+9.74 Bq/Kg), 238U (14.17+6.05 – 27.19+6.14 Bq/Kg) and 40K (104.07+29.78 – 302.74+60.11 Bq/Kg). The mean radium equivalent Raeq value obtained was 60.27 BqKg-1 which is lower than the limit of 370 Bq/Kg set by the Organisation for Economic Cooperation and Development. The absorbed gamma dose rate in air was estimated to be in the range of 20.12 – 39.44 nGyh-1 which is lower than the world average value of 55nGyh-1. The annual effective dose equivalent ranged from 24.68 – 48.37 µSv with an arithmetic mean of 34.65 µSv; it was also found to be lower the average value (70 µSv) recommended by the United Nations Committee on the Effect of Atomic Radiation (UNSCEAR). The results indicate that, at present, the radiation hazard from radionuclides in all the marble samples analyzed is within permissible limits. Therefore, it poses no radiation threat to the human population as well as other environmental elements living around these areas.