The inventory of gamma-emitting radionuclides was determined in soil samples collected at six depth levels, from 15 locations in Istanbul metropolis. The activity concentrations of (232)Th, (238)U, (40)K were measured by means of gamma spectrometry. The average activity concentrations of (232)Th, (238)U, (40)K in the 30-cm depth soil were found as 32.1, 27.4, 393.1 Bq kg(-1), respectively. The mean value of the absorbed dose rate (D), annual effective dose equivalent (AEDE) from the outdoor terrestrial gamma radiation, Ra equivalent activity (Ra(eq)), and the external hazard index (H(ex)) were calculated as 48.7 nGy h(-1), 59.7 muSv, 104.1 Bq kg(-1), and 0.28, respectively. The effects of organic matter content, textural properties, and pH value of soil samples on the natural radionuclide levels were also investigated. The relations between natural radionuclide level and the physical and chemical properties of studied soil samples were mainly clarified with cluster analysis and Pearson correlation.

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The activity concentrations of 137Cs, 40K, 232Th, 238U and 226Ra were measured in surface soil samples from East and South of Marmara region, Turkey. The physico-chemical parameters (organic matter, CaCO3 contents and pH-value) of the soil samples were determined in the samples collected from 100 sampling stations. The average activity concentrations of 137Cs, 40K, 232Th, 238U and 226Ra were found to be 27.46+/-21.84, 442.51+/-189.85, 26.63+/-15.90, 21.77+/-12.08 and 22.45+/-13.31 Bq kg(-1), respectively. The mean value of total annual external gamma radiation dose equivalent for the natural radionuclides was calculated to be 54.86 microSv. The current data were compared with those found in the other locations of Turkey and different countries.

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