科研之友
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摘要
Radiocesium (Cs-137) migration from headwaters in forested areas provides important information, as the output from forest streams subsequently enters various land-use areas and downstream rivers. Thus, it is important to determine the composition of Cs-137 fluxes (dissolved fraction, suspended sediment, or coarse organic matter) that migrate through a headwater stream. In this study, the Cs-137 discharge by suspended sediment and coarse organic matter from a forest headwater catchment was monitored. The Cs-137 concentrations in suspended sediment and coarse organic matter, such as leaves and branches, and the amounts of suspended sediment and coarse organic matter were measured at stream sites in three headwater catchments in Yamakiya District, located-35 km northwest of Fukushima Dai-ichi Nuclear Power Plant (FDNPP) from August 2012 to September 2013, following the earthquake and tsunami disaster. Suspended sediment and coarse organic matter were sampled at intervals of approximately 1-2 months. The Cs-137 concentrations of suspended sediment and coarse organic matter were 2.4-49 kBq/kg and 0.85-14 kBq/kg, respectively. The Cs-137 concentrations of the suspended sediment were closely correlated with the average deposition density of the catchment. The annual proportions of contribution of Cs-137 discharge by suspended sediment, coarse organic matter, and dissolved fraction were 96-99%, 0.0092-0.069%, and 0.73-3.7%, respectively. The total annual Cs-137 discharge from the catchment was 0.02-0.3% of the deposition.
- 出版日期2017-1
