量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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Radioactive carbon (14C) is the dominant radioactive nuclide in transuranic (TRU) waste. However, only a few studies to date have taken into account 14C transition in its gaseous form (14CO2). For an appropriate biosphere assessment of geological disposal, it is important to understand the degree of 14CO2 mixing with ambient air by vegetation. To evaluate the impacts of the structure of the plant community, relative to the vertical and horizontal wind speed, we characterized the structure of two gramineous plant communities (community-1, community-2) and compared the wind at three heights (middle, top, and above) of each community. The comparison of the two plant communities revealed that the biomass was the same, but the plant height of community-1 was 78% of that of community-2, and its vegetation density was approximately twice as high. Wind speeds of middle of the community with a higher vegetation density were less affected by the winds outside the community. It was assumed that the winds in the plant communities became more restricted as the community density increased. It is therefore suggested that effects of vegetation density are an important factor for the retention and the transition of 14CO2 to vegetation.
Impacts of height and density of gramineous plant community on internal wind speed -Toward safety assessments of TRU waste disposal-
