Effect of biological activity due to different temperatures on iodide partitioning in solid, liquid, and gas phases in Japanese agricultural soils

摘要

In this study, we experimentally obtained partitioning ratios of radioiodide (~(125)I~-) in the three phases at two different temperatures, 4 and 23 C, in order to observe the effect of biological activity for upland soil samples. Even at 4 C, ~(125)I emission was found; its partitioning ratio in the gas phase ranged from 0 to 27 %. As expected, the ratio at 23 C was higher than that at 4 C. Additionally, in comparison of the data for upland soil samples obtained in this study and our previous data for paddy soil samples, for the latter, I~- was not only sorbed in the soil but also more of it was released into the air than for upland soil samples. The land-use difference for I~- partitioning in soil might be attributed to the differences of exchangeable K and stable I concentrations in soil from the statistical analysis. On the other hand, there were good correlations of partitioning ratios in solid, liquid, and gas phases between the two temperatures. The results implied that the biological activity can enhance partitioning in not only the gas phase, but also the solid phase. Indeed, the soil-soil solution distribution coefficient at 23 C was about three times as high as that at 4 C.