Estimation of vertical migration velocity of 137Cs in the Mount IDA/Kazdagi, Turkey

Abstract

This paper presents the results obtained from a radioecological study carried out in the forest sites of Mount IDA (Kazdagi)/Edremit, Turkey. For 118 soil profiles, the depth distribution of 137Cs activity was established by fitting the experimental points to an exponential, a gaussian or a log-normal function. The relaxation lengths were in the range of 1.09–16.7 cm with a mean of 5.73 cm, showing a slow transport and a strong retention capacity of 137Cs even after the 26-y period of Chernobyl accident. From the data for the vertical distribution of 137Cs in soil profiles, the mean annual migration velocity of 137Cs was in the range of 0.11–0.62 cm year−1 with a mean of 0.30 cm year−1. Statistically significant correlations between the thickness of the humus layer and the mean annual velocity of 137Cs were found for both coniferous and mixed forest sites. The mean annual velocity of 137Cs in the forests sites with Pinus nigra var pallasiana was significantly higher than sites with Pinus brutia. External dose-rates from the 137Cs in forest soils were estimated using a conversion factor used in many studies and comprised with the external dose-rates determined according to the vertical distribution of 137Cs within the soil depth profiles. It is clearly seen that both levels and spatial distribution patterns of the external dose-rates from 137Cs were influenced considerably with the vertical migration rate and the vertical distribution of 137Cs.