Radionuclide concentrations in soil around waste dumpsites and its excess lifetime cancer risk due to gamma radioactivity in Ogbomoso metropolis, South-Western Nigeria.

Abstract

Radiation from waste dumpsite as well as certain antropogenic radionuclides released to the environment are major contribution to terrestrial outdoor exposure. This paper takes a look at the radiation level from twenty major waste dumpsites in Ogbomoso metropolis of Oyo State, Nigeria. Soil samples were taken from 100 locations for laboratory analysis with a very sensitive gamma ray spectroscopy Nal (Tl) scintillation detector. The outdoor gamma dose rates were determined by Alarm Dosimeter Geiger counter portable device and measurements were taken in air for two minutes at 1m from the ground. The outdoor gamma dose rate range from 16.53 to 42.51nGy/h. Annual effective dose rate varied from 0.021 to 0.053mSv/y and the excess lifetime cancer risk within the metropolis range from 0.05x10-3 to 0.12x10-3. It was observed that the concentration of radionuclides viz.226 R234Th 40K and 134 Cs in samples ranges from 7.30 to 35.06Bq/kg, 10.44 to 28.44Bq/kg, 56.42to 1000.42Bq/kg and 7.60Bq/kg, respectively. The soil radio nuclides” concentrations of the study and annual effective gamma dose were within the worldwide range. Excess lifetime cancer risk is far below worldwide range of 0.29x10-3 (UNSCEAR, 2000) 134Cs detected was due to fission of heavy radionuclide that may be present in the dump site.