Characterization of fallout deposition materials during 1993-2005 at Tokai-mura by radioanalytical methods

Characteristics of fallout deposition materials collected during 1993-2005 at Tokai-mura were carried out by radioanalytical methods. The deposition samples were taken by a basin (surface area of 0.5m2) during one month, and dried-up, powdered by an agate mortar. The 14C/12C ratios were measured for the samples in March of 1996, 1998, 2000, 2002 and 2004 by accelerator mass spectrometry at the NIFS. Deposition fluxes of organic carbon ranged from 0.11 to 2.25 g/cm2/month, showed two peaks in spring and autumn every each year, and almost showed maximum in spring. The Δ14C values were from -80.2 to -5.5 per mille. When the Δ14C values were plotted as a function of deposition flux of organic carbon, it appears the correlation between Δ14C and TOC flux. These values suggest that organic carbon deposited in each year may be mixed with newly formed and old organic carbon. (author)