Determination of natural and artificial radioactivity in soil at North Lebanon province

Abstract

The concentrations of natural and artificial radionuclides at 57 sampling locations along the North Province of Lebanon are reported. The samples were collected from uncultivated areas in a region not previously reported. The samples were analyzed by gamma spectrometers with High Purity Germanium detectors of 30% and 40% relative efficiency. The activity concentrations of primordial naturally occurring radionuclides of 238U, 232Th, and 40K varied between 4–73 Bq kg−1, 5–50 Bq kg−1, and 57–554 Bq kg−1 respectively. The surface activity concentrations due to the presence of these radionuclides were calculated and Kriging-geostatistical method was used to plot the obtained data on the Lebanese radioactive map. The results for 238U, 232Th, and 40K ranged from 0.2 kBq m−2 to 9 kBq m−2, from 0.2 kBq m−2 to 3 kBq m−2, and from 3 kBq m−2 to 29 kBq m−2 respectively. For the anthropogenic radionuclides, the activity concentrations of 137Cs founded in soil ranged from 2 Bq kg−1 to 113 Bq kg−1, and the surface activity concentration from 0.1 kBq m−2 to 5 kBq m−2. The total absorbed gamma dose rates in air from natural and artificial radionuclides in these locations were calculated. The minimum value was 6 nGy h−1 and the highest one was 135 nGy h−1 with an average of 55 nGy h−1 in which the natural terrestrial radiation contributes in 99% and the artificial radionuclides mainly 137Cs contributes only in 1%. The total effective dose calculated varied in the range of 7 μSv y−1 and 166 μSv y−1 while the average value was 69 μSv y−1 which is below the permissible limit 1000 μSv y−1.