@inproceedings{oai:repo.qst.go.jp:00054100,
 author = {Ishii, Nobuyoshi and Takeda, Hiroshi and Uchida, Shigeo and 石井 伸昌 and 武田 洋 and 内田 滋夫},
 book = {The International Conference on Radioecology & Environmental Radioactivity 15-20 June, 2008 in Bergen, Norway : Proceedings Oral and Oral Poster Presentations},
 month = {Jun},
 note = {Transuranic (TRU) waste containing some radionuclides is generated during the operation of reprocessing facilities.  The dominant nuclides contributing to the dose from TRU waste are iodine-129 and carbon-14.  Since these nuclides are long-lived, soluble and have very little sorption properties, they are the key nuclides in safety assessment for a geological repository of TRU waste.  Recently, the possibility of leaching of carboxylic acids such as formic acid and acetic acid from TRU waste has been reported.  However, the behavior of these chemicals does not fully understand.  Understanding of the behavior, for example the distribution coefficients (Kd) and gasification ratio, can be required for appropriate safety assessment.  In the present study, we estimated Kd values and gasification ratio of sodium acetate for a flooded soil and studied factors affecting these behaviors.
\nA soil collected from a paddy field in Japan was flooded with deionized water (DIW) and well water (WW) at a solid-liquid ratio of 1:10.  To investigate the effect of microorganisms existing in these waters, the filter-sterilized waters were also used for flooding.  The flooded samples supplemented with [1, 2-14C] sodium acetate (14C-NaOAc) were shake-incubated for 7 days.  At the end of the incubation, each of the samples was separated to solid and liquid phase using a filter (0.2 µm pores), and radioactivites of 14C-NaOAc in the slurry of the flooded sample and its liquid phase were determined with a liquid scintillation counter.  The Kd values and gasification ratios were determined using the values obtained by liquid scintillation counting.
\nA radioactive tracer experiment was also carried out using DIW without the soil.  Radioactivity of 14C-NaOAc in the DIW was decreased from 1.7 to 0.9 kBq mL-1 during the shake-incubation, but no decrease was found when the DIW water was filter-sterilized.  The results suggest the presence of NaOAc-assimilating bacteria (NaOAc-AB) in DIW.  We isolated and identified the bacterium.  The microscopic observation showed that the bacterium was gram-negative aerobic bacteria with rod shape, and 16S rRNA gene sequence was corresponded to that of Burkholderia gladioli.
\nThe value of Kd and gasification ratio of the soil which flooded with DIW were 138 and 68%, respectively.  When the filter-sterilized DIW was used for flooding, these values were 93 and 69%, respectively.  There were no statically differences between the DIW sample and the filtered DIW sample for those values.  The NaOAc-AB would not affect on both kd value and gasification ratio under our laboratory conditions.  Similar results were found for the WW samples.  However, the Kd values of the WW sample and the filter-sterilized WW sample were significantly low compared to those of the DIW sample and the filtered DIW sample.  Similar results were also obtained from gasification ratios.  Since pH values of DIW and WW were 5.5 and 8.5, respectively, pH may be one of factors affecting the behavior of 14C-NaOAc.
\nThis work has been partially supported by the Agency for Natural Resources and Energy, the Ministry of Economy, Trade and Industry (METI) Japan.},
 pages = {378--381},
 publisher = {Norwegian Radiation Protection Authority},
 title = {Migration behavior of [1,2-14C] sodium acetate in a flooded soil},
 volume = {Part 2},
 year = {2008}
}