Radioactivity Levels and Gamma-Ray Dose Rate in Soil Samples from Kohistan (Pakistan) Using Gamma-Ray Spectrometry

The analysis of naturally occurring radionuclides (Ra-226, Th-232 and K-40) and an anthropogenic radionuclide Cs-137 is carried out in some soil samples collected from Kohistan district of N.W.F.P. (Pakistan), using gamma-ray spectrometry. The gamma spectrometry is operated using a high purity Germanium (HPGe) detector coupled with a computer based high resolution multi channel analyzer. The specific activity in soil ranges from 24.72 to 78.48 Bq.kg(-1) for Ra-226, 21.73 to 75.28 Bq.kg(-1) for Th-232, 7.06 to 14.9 Bq.kg(-1) for Cs-137 and 298.46 to 570.77 Bq.kg(-1) for K-40 with the mean values of 42.11, 43.27, 9.5 and 418.27 Bq.kg(-1), respectively. The radium equivalent activity in all the soil samples is lower than the safe limit set in the OECD report (370 Bq.kg(-1)). Man-made radionuclide Cs-137 is also present in detectable amount in all soil samples. Presence of Cs-137 indicates that the samples in this remote area also receive some fallout from nuclear accident in Chernobyl power plant in 1986. The internal and external hazard indices have the mean values of 0.48 and 0.37 respectively. Absorbed dose rates and effective dose equivalents are also determined for the samples. The concentration of radionuclides found in the soil samples during the present study is nominal and does not pose any potential health hazard to the general public.