Chemical states of stable Zn and aging effect of 65Zn in the soil.

Aging effect/Isotopic exchange reaction/Isotopic dilution/DTPA extractable Zn/Labile form of Zn The amount of stable Zn and the specific activity (S.A.) of 65Zn in DTPA extract were pursued as a function of time after the administration of 65Zn to Tanashi volcanic ash soil and Naka-gawa lluvial soil to investigate chemical states of Zn in the soils and also aging effect of 65Zn introduced to the soils. There were at least 3 kinds of Zn pools, i.e., rapid exchange pool (pool A; possibly soil solution), ex change pool (pool B; several tens of days are needed to attain in isotopic exchange equilibrium), and very slow exchange pool (pool C; several thousand days are needed to reach isotopic exchange equilibrium). The aging effect was not clearly observed because 65Zn i troduced into the soil remained in an available fraction (in pool A and B) for relatively long days.