Shinji Sugihara

An improved method for 85Kr analysis by liquid scintillation counting and its application to atmospheric 85Kr determination

Atmospheric (85)Kr concentration at Fukuoka, Japan was determined by an improved (85)Kr analytical method using liquid scintillation counting (LSC). An average value of 1.54 +/- 0.05 Bq m(-3) was observed in 2008, which is about two times that measured in 1981 at Fukuoka, indicating a 29 mBq y(-1) rate of increase as an average for these 27 years. The analytical method developed involves collecting Kr from air using activated charcoal at liquid N(2) temperature and purifying it using He at dry ice temperature, followed by Kr separation by gas chromatography. An overall Kr recovery of 76.4 +/- 8.1% was achieved when Kr was analyzed in 500-1000 l of air. The Kr isolated by gas chromatography was collected on silica gel in a quartz glass vial cooled to liquid N(2) temperature and the activity of (85)Kr was measured with a low-background LS counter. The detection limit of (85)Kr activity by the present analytical method is 0.0015 Bq at a 95% confidence level, including all propagation errors, which is equivalent with (85)Kr in 1.3 l of the present air under the analytical conditions of 72.1% counting efficiency, 0.1597 cps background count rate, and 76.4% Kr recovery.

Adsorption of Fe(III), Co(II) and Zn(II) onto particulates in fresh waters on the basis of the surface complexation model I. Stabilities of metal species adsorbed on particulates

Abstract Particulates, fine sediments and residue from evaporation of the filtrate from fresh waters were sequentially extracted with several reagents, and concentrations of iron, manganese, cobalt and zinc were determined. Iron(III) and Co(II) in particulates were similar to those in fine sediments in both their contents and chemical forms. Concentrations of Zn(II) and Mn in particulates were higher than those found in fine sediment, and considerably different in their chemical speciation. The difference between Fe and Mn may be due to the difference in their oxidation potentials. The difference between Co and Zn may depend on their affinity for Fe or Mn oxides. Distributions of Fe(III), Co(II) and Zn(II) between particulates and water were determined and compared with those predicted on the basis of the surface complexation model. These results are generally consistent with theories that metal species dissolved in water exist as free ions or are considerably less stable than their surface complexes on particulates.

Biodiffusion of 7Be and 210Pb in intertidal estuarine sediment

Abstract The profiles of 7 Be and 210 Pb in three kinds of sediments from the intertidal zones of the Tatara-Umi estuary, Fukuoka, Japan were measured. In a silty area, they were fitted on a simple biodiffusion model with the diffusion coefficients of (1–8) × 10 −7 cm 2 s −1 . Radioactive tracers of 22 Na, 85 Sr, 134 Cs, 59 Fe, 54 Mn, 57 Co and 65 Zn were added to the untreated or heated cores of the undisturbed sediments to examine bioactivity on the transfer of the radionuclides In the heated cores, paniculate tracers were hardly transferred. In the untreated cores, they were diffused heterogenously and showed peaks at intermediate depths, which suggested biodiffusion with conveyor-belt deposit feeders. Paniculate radionuclides in estuarine sediment in the silty area are supposed to be biodiffused mainly with macroorganisms such as crabs and bivalves.

Transfer of 7Be, 210Pb and 210Po in a forest canopy of Japanese cedar

The concentrations of 7Be, 210Pb and 210Po of ca. 60 parts of a whole tree of Japanese cedar and of underlying litter and soil samples were determined for studying their transfer in a forest canopy. The results suggest that the mean residence times of 7Be and 210Pb in the forest canopy were ca. 20 and 900 days, respectively, and the dry deposition rate of 7Be on the forest canopy was about a half of the total deposition rate.

Mössbauer studies of first-stage corrosion products on iron powder and corrosion products on highly corroded nails

Abstract Magnetic iron powders were treated in solutions containing NaCl or CH 3 COONa as corrosion agents at 298 K and the oxide layers produced on the iron surface were identified by means of Mossbauer spectrometry. The measurement of Mossbauer spectra at various temperatures was useful to assign the chemical species produced on the surface. The spectra consisted of the superparamagnetic doublet peaks of polymorphic forms of FeOOH at room temperature. Highly corroded nails collected from different environments, i.e. sea coast, volcanic hot spring and an inland house, were examined to characterize the atmospheric corrosion products of nails. As a result, it was found that a -FeOOH and γ-Fe 2 O 3 were present in every case. β-FeOOH and Fe 3 O 4 were detected in nails collected at sea coast, volcanic hot spring and an inland house, respectively. The above results show that chemical pollution in the atmosphere is reflected in the species of corrosion products of nails exposed. Long-time exposure of nails resulted in the formation of γ-Fe 2 O 3 and a -FeOOH.

Atmospheric deposition of35S

The35S content in atmospheric deposition, aerosol and rain water was determined about every 10 days for a year with7Be,32P and some stable elements. Average35S concentrations were 110 mBq·m−2·d−1 for atmospheric deposition, 0.078 mBq·m−3 for aerosol in surface air and 45 mBq·l−1 for rain water. The ratios of7Be/35S were abnormally low, although most of32P/7Be showed the reasonable values corresponding to the residence times from 10 to 60 days. The excess35S suggests an external source of35S or/and a faster cycle of35S than that of7Be and32P.

Effects of metal ions and organic ligands on the adsorption of Co(II) onto silicagel

Cobalt(II) ions were adsorbed onto silicagel from solutions containing metal ions and organic ligands. Levels of < 10−4M Ca(II), Zn(II), Fe(III) and Mn(II) did not affect adsorption, while 10−3M Fe(III) and Mn, as hydroxides, enhanced adsorption in the low pH region. Glycine, nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) lower the rate of adsorption, as the surface complexation model predicts, but ethylenediamine did not interfere with adsorption. Humic and fulvic acids lowered the rate of adsorption in approximately the same manner as glycine. These effects are discussed in relation to the application of the surface complexation model to the adsorption of trace metal ions on particulates in fresh waters.

Movement of radiocaesium fallout released by the 2011 Fukushima nuclear accident

The moment magnitude (Mw) 9.0 Tohoku-Oki Earthquake occurred on March 11, 2011, generating an unusually large tsunami. The seismic shocks and tsunami inundation severely damaged the Fukushima Daiichi Nuclear Power Plant. Radionuclide emission due to reactor breakdown contaminated wide areas of Fukushima and its surroundings. Heavy rainfall causes runoff across surface soil, and fine soil particles are susceptible to uptake by the flowing water. The high radioactivity of grains suspended in floodwater indicates that radioactive fallout was streamed into rivers in particulate form and transported downstream under high-flow conditions. Here, we investigated the diachronic mode of 134Cs and 137Cs in central Fukushima, through which the contaminated air mass drifted and caused wet deposition of radionuclides. Stratigraphic measurements of radioactivity in sediment cores is the method employed in this study to determine the basin-wide movement of 134Cs and 137Cs, to evaluate the significance of the erosion–transportation–accumulation processes on natural decontamination in terrain characterized by steep slopes and high precipitation. Stratigraphic results illustrate the process of fluvial sediment discharge, and the massive deposition of radiocaesium suggests basin-wide movement of fallout during concentrated rainfall. Grain suspension in torrential currents is an important pathway for transportation of radionuclides from land to sea, and the appearance of hotspots on floodplains and the offshore sea floor is the consequence of erosion and transportation under seasonal heavy precipitation. Radioactive horizons occur in offshore sediment columns and thus radiocaesium discharged from the estuary will persist forever under the sea floor if no artificial disturbance occurs.

Local structures and electronic band states of α−Fe2O3 polycrystalline particles in the glazes of the HIZEN celadons produced in the Edo period of Japan, by means of X-ray absorption spectra (II)

HIZEN celadon glazes produced in 1630s to 1790s (Edo period, Japan) have been investigated by means of X-ray absorption spectra (XAS) near a Fe-K edge by using synchrotron radiation and a Mossbauer spectrum. The XAS suggest that the local structure around Fe2O3 fine powders is slightly different between the Izumiyama ceramics of mainly the Quartz-SiO2 and Ohkawachi ceramics of mainly the feldspar of (K,Na)Si3O8 (Sanidine), and that the glazes of the HIZEN celadons include the Fe2O3 fine powders in the glassy state, though the X-ray diffraction patterns of the glassy celadon glazes do not show any peaks of the Fe2O3 structure. The Mossbauer spectrum suggests that the celadon glaze of Seiji (m) includes only Fe3+ ions, but not Fe2+ ions. This indicates the existence of Fe2O3 in the celadon glaze. It is interpreted that the colored brightness of the HIZEN celadons is induced by the structural properties of the used raw celadon ceramics and the other transition-metal ions of Cr, Cu, Zn in the celadon glazes, but not by the chemical reaction from Fe2O3 to FeO under the deoxidizing thermal treatment at higher temperature in a kiln.

Distribution and mean residence time of natural radionuclides in the forest ecosystem

Activity concentrations of radionuclides,7Be,210Pb and210Po, in precipitation (rain, throughfall and stemflow), wood and soil were determined by using gamma-ray and alpha-ray spectrometry to estimate the migration behavior of these radionuclides in the forest canopy. The activity ratios between output and input precipitations for the forest canopy were 0.53 of7Be, 0.79 of210Pb and 1.5 of210Po for Pasania edulis forest. A dynamic model of the transport and fate of radionuclides in the forest ecosystem was constructed. Mean residence times of radionuclides were 56 days for7Be, 765 days for210Pb and 653 days for210Po for Pasania edulis forest.