Review of Distribution of Natural Radiation in Some Parts of Nigeria

Activity concentrations of natural radioactivity of 40K, 238U, 226Ra, and 232Th were reviewed in connection with rock, soil, sediments, and water in the Northern and Southern parts of Nigeria to estimate the radiation dose acquire by the population. The activity concentrations of the various radionuclides from rock samples collected from different locations were generally higher than those of other environmental matrices. Comparative distribution maps of 40K, 238U, and 232Th show the distribution of activity concentration in the Northern and Western part of Nigeria. The activity concentrations 40K, 238U, and 232Th in rock ranges from 40 Bq kg-1 to 1203 Bq kg-1, 34 Bq kg-1 to 7220 Bq kg-1, and 8 Bq kg-1 to 1680 Bq kg-1 respectively. In soil it ranges from 98.7 Bq kg-1 to 1023.3 Bq kg-1, 15.6 Bq kg-1 to 55.3 Bq kg-1, and 5.2 Bq kg-1 to 195.5 Bq kg-1 respectively. In sediment it ranges 97 Bq kg-1 to 1023 Bq kg-1, 12 Bq kg-1 to 47.9 Bq kg-1, and 11.7 Bq kg-1 to 55.3 Bq kg-1. The concentration of 40K and 238U in granite rocks are higher than the recommended permissible value. All the water samples were found to contain acceptable levels of radionuclides with mean activity values of 3.98±0.26, 11.00±2.58, and 17.73±5.04 Bql-1 for 40K, 232Th, and 238U, respectively showing that the mean activity of 238U for all the samples is the highest when compared with those of 40K and 232Th. The mean absorbed dose rate for all the area is 0.123mSvyr-1, which is very low when compared to the recommended limit of 1mSvyr-1 for water.