Dosimetric depth distribution of Fukushima-derived 137Cs in coniferous forest soil

The ambient dose rate (ADR) in a coniferous forest floor contaminated by Fukushima-derived 137Cs was calculated for small temporal scale as a function of depth. The calculated total ADR was statistically evaluated along the soil vertical strata and among the sampling time series. Moreover, the contribution of the forest floor components to the total radiation dose were examined. Accordingly, the litter and fragmented organic layers accounted for about 58 to 96% (mean 77 ± 14%) of the ambient dose, indicating the organic layer is a chief sources of external radiation exposure, and an important radiological soil section.