Analysis of radiocaesium in the Lebanese soil one decade after the Chernobyl accident

Fallout from the Chernobyl reactor accident due to the transport of a radioactive cloud over Lebanon in the beginning of May 1986 was studied 12 years after the accident for determining the level of 137Cs concentration in soil. Gamma spectroscopy measurements were performed by using coaxial high sensitivity HPGe detectors. More than 90 soil samples were collected from points uniformly distributed throughout the land of Lebanon in order to evaluate their radioactivity. The data obtained showed a relatively high 137Cs activity per surface area contamination, up to 6545 Bq m−2 in the top soil layer 0-3 cm. The average activity of 137Cs in the top soil layer 0-3 cm in depth was 59.7 Bq kg−1 dry soil ranging from 15 to 119 Bq kg−1 dry soil. The horizontal variability was found to be about 45% between the sampling sites. The depth distribution of total 137Cs activity in soil showed an exponential decrease. Estimation of the annual effective dose due to external radiation from 137Cs contaminated soil for selected sites gave values ranging from 19.3 to 91.6 μSv y−1.