Persistence of 137Cs in the litter layers of forest soil horizons of Mount IDA/Kazdagi, Turkey

In 2010-2012, an extensive study was performed in forest sites of Mount IDA (Kazdagi)/Edremit 26 years after the Chernobyl accident. The 137Cs activity concentrations were determined by gamma-ray spectrometry in the forest soil layers (OL, OF + OH and A horizons) separately. Based on 341 surface soil samples and 118 soil profiles, activity concentrations of 137Cs in OL horizons varied between 0.25 ± 0.14 and 70 ± 1 Bq kg−1, while the ranges of 137Cs activity concentrations in OF + OH and A horizons were 13 ± 1-555 ± 3 Bq kg−1 and 2 ± 1-253 ± 2 Bq kg−1, respectively. Cesium-137 deposition in the study area was estimated to be in the range of 1-39 kBq m−2 and a linear relationship between the deposition of 137Cs and the altitude was observed. The distributions of 137Cs activities in OL, OF + OH and A horizons throughout the region were mapped in detail. The highest 137Cs activities were found in OF + OH horizons, with markedly lower 137Cs activity in mineral horizons of soil profiles. It is observed that 137Cs content of humus layer increases with the thickness of the humus layer for coniferous forest sites. The 137Cs activity concentrations were higher than the recommended screening limits (150 Bq kg−1) at some of the investigated areas. The current activity concentration of top soil layers indicates that over many years since the initial deposition, 137Cs activity is keeping still high in the organic horizons.