The behavior of technetium in soil surface water

The physicochemical modification of technetium (Tc) was determined in surface water covering paddy fields to obtain basic data for Tc behavior in paddy fields. The Tc form was changed from TcO4- to another form. The modification was mainly in solubilization. The relative amount of insoluble Tc increased with time until day 4 from the addition of Tc to a surface water sample, and the same level of insoluble Tc as on day 4 was also observed on day 42. Such insoluble Tc may precipitate and accumulate on surface soil layer of paddy soils over time. The factor causing insoluble Tc would be microorganisms since little change in the forms of Tc was observed in a filtered and an autoclaved surface water sample, where no living microbial cells were present. The addition of an antibiotic fungicide, cycloheximide, resulted in little change in the relative amount of insoluble Tc, while a mixture of prokaryotic antibiotics caused a decrease of the insoluble Tc amount. Among microorganisms, bacteria would contribute to the insoluble Tc formation in surface water samples. (author)