@misc{oai:repo.qst.go.jp:00068598,
 author = {Ishii, Nobuyoshi and Koiso, Hiroyuki and Takeda, Hiroshi and Uchida, Shigeo and 石井 伸昌 and 小礒 寛之 and 武田 洋 and 内田 滋夫},
 month = {Jul},
 note = {Technetium-99 is a radioactive contaminant in marine and terrestrial environments. Under oxic conditions, it is present as the pertechnetate anion [Tc(VII)O4-], which is soluble and mobile in the environment. In paddy fields in Japan, the accumulation of Tc in the 20-cm plow layer was observed (Tagami and Uchida 2002). Since paddy fields are flooded during the planting season, reductive conditions develop in the plowed layer. Under reductive conditions, Tc is transformed from Tc(VII) O4- to Tc(IV) species. Tc(IV) species generally are insoluble and immobile in the environment, and thus Tc(IV) could accumulate in the plowed layer.
Recently, it was found that gram-negative-bacteria were responsible for the formation of insoluble Tc in the ponding water of flooded paddy fields (Ishii and Uchida 2005). This insolubilization would be one of the factors of the Tc accumulation in the plowed layer because bacteria sink into the plowed layers due to their own weight over time. However, little information is available for environmental conditions of Tc insolubilizing by the bacteria. In this study, optimum oxic conditions for the insolubilization were determined., 18th World Congress of Soil Science},
 title = {Environmental conditions for insoluble Tc formation in ponding water above a paddy field},
 year = {2006}
}