VERTICAL DISTRIBUTIONS AND GAMMA DOSE RATES OF 40K, 232Th, 238U AND 137Cs IN THE SELECTED FOREST SOILS IN IZMIR, TURKEY

This paper presents the results obtained from a radioecological study carried out in the selected forest sites of Izmir, Turkey. The levels of gamma-emitting radionuclides, K-40, Th-232, U-238 and Cs-137, in soils were determined using gamma spectroscopy. The activity pro. le for 40K, 232Th and 238U exhibits a uniform distribution with respect to depth. The depth distribution of Cs-137 activity was established by fitting the experimental points to an exponential or a Gaussian function. About 42-97% of the Cs-137 deposition was found in the first 10 cm of soil even after 18 y from Chernobyl accident. The dose-rate and annual-effective dose received from external irradiation were quantified. It is indicated that 137Cs from the fallout plays a less role in external radiation exposures in forest sites of Izmir than in potential exposures from naturally occurring radionuclides accounted for by soil.