2015 Fiscal Year Annual Research Report
Study of stable cesium for the long-term prognosis of radiocesium cycling in forest ecosystems after Fukushima NPP accident
Publicly Offered Research
| Project Area | Interdisciplinary Study on Environmental Transfer of Radionuclides from the Fukushima Daiichi Nuclear Power Plant Accident |
|---|
| Project/Area Number |
15H00968
|
|---|
| Research Institution | Fukushima University |
|---|
Principal Investigator |
Yoschenko Vasyl 福島大学, 環境放射能研究所, 特任教授 (40745569)
|
|---|
| Project Period (FY) |
2015-04-01 – 2017-03-31
|
| Keywords | Fukushima accident, / radiocesium / stable cesium / forest ecosystems / radiocesium fluxes |
|---|
| Outline of Annual Research Achievements |
The general aim of the project is quantification of the radiocesium fluxes in the typical Fukushima forest at the late stage after the deposition. The key issue is distinguishing between the radiocesium activities in the ecosystem compartments caused by the root uptake and those remaining in biomass after the initial deposition. For this purpose we measure the distribution and fluxes of the stable cesium in the forest ecosystem, which are formed by its root uptake.
We sampled biomass in the aboveground compartments of the Japanese cedar forest at the experimental site in Yamakiya as it was planned for FY 2015 and measured the stable cesium concentrations in the samples. The results were compared to the radiocesium activity concentrations measured in the same samples. Based on the concentration ratios of the stable to radioactive cesium, we estimated the radiocesium activity fractions in the biomass remaining after the initial deposition (present mainly in the outer bark and older foliage). Also, we measured the stable cesium concentrations in througfall and stemflow and calculated its annual fluxes. The preliminary assessment of the cesium biogenic fluxes in the studied ecosystem was done. The soil and litter samples were collected too. The stable cesium concentration measurements and determination of its chemical forms in these samples are in progress now.
As compared to the initial plan for FY 2015, we extent our study to the new experimental site in Tsushima and began the measurements of the stable cesium concentrations in the samples collected at this site.
|
| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The main results expected for the FY 2015 have been achieved. As it was mentioned above, as compared to the initial plan we added the new experimental site in order to characterize variability of the studied parameters; however, the measurements for this site are in progress now as well as the measurements of the stable cesium concentrations in the soil and litter samples from the experimental site in Yamakiya. Also, we postponed for FY 2016 the characterization of the root system distribution by depth (was planned for the end of FY 2015 or the beginning of FY 2016).
|
| Strategy for Future Research Activity |
During FY 2016 the measurements of the stable cesium concentrations in the collected samples of soil and litter from the Yamakiya forest site and the biomass, soil and litter from the Tsushima site will be completed. Based on the measurement results, the stable cesium distributions in the ecosystems will be specified and the numerical values of its fluxes (incorporation, uptake, immobilization, return and translocation) will be calculated.
Study of the stable cesium forms in the samples of stemflow, throughfall and soil at the Yamakiya site will be continued. New sampling will be carried out.
The stable cesium concentrations will be also measured in the tree biomass compartment samples collected at several other observation sites in the Fukushima prefecture in order to generalize the regularities obtained at the Yamakiya and Tsushima sites.
We will also carry out characterization of the studied tree species root system vertical distribution in soil profile by its capacity to absorb cesium.
By the end of the FY2016, the comprehensive set of data describing the stable cesium dynamics in the forest ecosystem will be gained. The principal results will be submitted for publication in the international journal.
|
