Yoko Fujikawa

Factors affecting interaction of radioiodide and iodate species with soil

Abstract The uptake of radioiodide and iodate species by soil dried at 100 °C (particle size of less than 0.25 mm) was studied in laboratory batch experiments for three major groups of variables: (i) experimental conditions (ambient temperature, liquid-to-solid ratio and contact time), (ii) solid phase conditions (grain size and washing treatment), and (iii) liquid phase conditions (pH, and concentrations of electrolytes and carrier). Effects of the presence of soluble and insoluble organic matter were also investigated in relation to radioiodine uptake by the soil. Plural uptake mechanisms were considered for iodide species, while a simple anion exchange process for iodate.

Vertical distributions of trace metals in natural soil horizons from Japan. Part 1. Effect of soil types

To predict the long-term behavior of trace metals in a soilprofile, we studied the vertical distributions of barium, zinc,copper, chromium, nickel, cobalt, lead, and the principalmetals, aluminum, iron and manganese, in three soils withdeveloped horizons obtained from rural areas in Japan. Totalelement analysis and selective extraction tests with variousreagents were conducted to clarify the extractability of themetals at each sampling depth.Soil-b (Dystric Cambisols) had the highest extractability ofelements although the vertical distributions of its traceelements were similar to those of soil-d (Umbric Andosols),which had to lowest metal extractability of the three soils.Soil-KUR (Orthic Acrisols or Dystric Cambisols) was the oldest of the three soils and showed downward movement of some tracemetals (chromium and nickel) and principal elements (Fe and Mn)that was probably induced by long-term weathering.The extractability of manganese, zinc and barium with water washigher than other metals examined in all three soils. Lead andcobalt in soil-b and soil-KUR also were considered to have highextractability under long-term weathering processes. Zinc andlead accumulated near soil surface showed higher extractabilitywith every reagent used than those in deep layers of the three soils.

Strong association of fallout plutonium with humic and fulvic acid as compared to uranium and137Cs in Nishiyama soils from Nagasaki, Japan

To investigate the formation of mobile organic plutonium, we analyzed the plutonium contents of the fulvic (FA) and humic (HA) acids from the soil samples obtained at Nishiyama, Nagasaki, Japan. The percentages of the plutonium bound strongly to HA and to FA vs. the total plutonium in the soil were 5–10% and 1%, respectively, at the depth of 0–0.1 m, much higher values than those of137Cs and uranium. After being weathered for 51 years under a temperate climate, the initial highfired oxides of fallout plutonium have become as chemically reactive plutonium from nuclear fuel reprocessing plants.

Adsorptive solute transport in fractured rock: analytical solutions for delta-type source conditions☆

Abstract Solutions for adsorptive solute transport equations in a single fracture-rock system were derived under two different delta-type source conditions. One was the delta-type, flux injection condition. The correspondent solution can be used for the analysis of experimental column breakthrough curves obtained by injecting the tracer into the rock fracture. The other was the delta-type, resident fluid injection condition. The solution can be used for the crude estimation of pollutant migration from the underground radioactive waste repository. In formalizing the resident fluid injection, an initial distribution of solute between solution and solid phase was assumed in order to satisfy the mass balance between injected and detected solute. Each of the two solutions was also expressed in two ways reflecting the flux and the resident fluid detection. Solutions expressed in terms of the flux detection correspond to the effluent concentration measured experimentally by a fraction collector system. On the other hand, solutions expressed in terms of the resident fluid detection describe spatial distribution of the solute in the fluid. Since considerably long tailings of breakthrough curves are often observed in column tracer experiments using fractured rocks effects of some parameter values on the tailing were also discussed. It was shown that the adsorption of solute rock matrix caused longer tailing. It was also shown that the resident fluid injection caused longer tailing of breakthrough curves than the flux injection condition.

Analysis of trace actinide elements in soil organic matter: Optimization of sample processing to improve chemical separation of U and Pu

Chemical separation yield of actinide elements from soil samples containing high amounts of organic matters was often low as compared to that for samples containing low organic matters. We compared chemical yield of uranium and plutonium from organic-rich Japanese soil and humic acid samples which were subjected to three different pretreatment procedures ((1) pulverization only, (2) dry-ashing at 510 °C after pulverization, and (3) 680 kGy gamma-ray irradiation after pulverization) prior to acid digestion. Separation of U and Pu was performed by U-TEVA resin and AG1-X8 anion exchange resin, respectively. For organic samples, pretreatment procedures governed the yield of actinide elements significantly. Chemical separation yield of U was low (6±1%) for Aldrich humic acid sample after dry-ashing at 510 °C. For such samples, gamma-ray irradiation improved the yield of U to 35±22%. Recovery of Pu was lower for some organic soil samples which were dry-ashed at 510 °C (27±2%) as compared to those which were not dry-ashed (62±10%).

A STUDY OF THE ATMOSPHERIC BOUNDARY LAYER USING RADON AND AIR POLLUTANTS AS TRACERS

Concentrations of radon 222Rn andair pollutants, meteorological parametersnear the surface and vertical profiles of meteorological elements were measured atUchio (Okayama City, Okayama Prefecture, Japan) 12 km north from the coast ofthe Inland Sea of Japan. In the nighttime, the 222Rn concentration increased in the case of weak winds, but did not increase as much in the case of moderate or strong winds, as had been expected. In the daytime, the 222Rn concentrationheld at a slightly higher than average level for the period from sunrise to about 1100 JST. It is considered that this phenomenon is due to a period of morning calm, that is, a transition period from land breeze to sea breeze.NO, which is sensitive to traffic volume,brought information concerning advection.Oxidant concentrations,which reflect the availability of sunlight,acted in the reverse manner to 222Rnconcentrations. Thus, a set of 222Rn and air pollutants could provide useful information regarding the local conditions of the atmospheric boundary layer.

Analysis of radioactive cesium and cobalt adsorption to rocks using the two-site kinetic model equations

The present study shows that equations of the two-site kinetic model, which have been applied to trace-metal and pesticide adsorption to soil, could also be used to simulate diffusion-controlled adsorption behaviour of 60Co and 137Cs to rock powder (diameter less than 105 × 10−5m), pieces (diameter 2 × 10−3m ∼ 3 × 10−3m) and slabs (0.05 m × 0.05 m × 0.01 m) of chert, shale and granodiorite in saline water. The adsorption rate coefficient was dependent on sizes of rocks and rock pore structures but was independent of distribution coefficients. The desorption rate coefficient was dependent on sizes of rocks, rock pore structures and distribution coefficients. The difference in adsorption and desorption rate coefficients between rock powder, pieces, and slabs was zero to two orders of magnitude for 137Cs and zero to three orders of magnitude for 60Co. Theoretical relationships between parameters of the two-site kinetic model and the Fickian diffusion model were also developed. Effective diffusion coefficients could be evaluated from the fitted rate parameter values of the two-site kinetic model. Observed characteristics of rate parameters agreed well with the theoretical equation. Dependence of adsorption and desorption rate coefficients and equilibrium distribution coefficient of 137Cs and 60Co on solid to liquid ratios were insignificant for rock powder. Applying rate parameter values obtained in this study to field conditions, it was concluded that kinetics of adsorption may often become important in predicting field-scale solute transport.

Anomalous 235U/238U ratios and metal elements detected in the black rain from the Hiroshima A-bomb.

Abstract— Contents of black rain from the A-bomb are important to clarify the health and environmental hazard caused by nuclear warfare. We analyzed the only existing physical remains of the black rain from Hiroshima A-bomb (Little Boy), a plastered wall with black streaks. Excess 137Cs and anomalous 235U/238U ratios detected in the black residues on the wall confirmed that the black streaks on the wall originated from Little Boy. The results also showed that excess 235U could be used as a fingerprint to clarify the distribution of materials discharged from Little Boy into the environment. High concentrations of lead and zinc, which may have caused a degree of heavy metal pollution in the area where the rain fell, were also detected in the black rain sample.

Determination of trace amounts of heavy metals in arctic ice core samples using inductively coupled plasma mass spectrometry

Trace amounts of heavy metals in the ice cores from Canadian Arctic were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). A custom made plastic device and ceramic knives were used to remove the contamination on the ice core surface. Ice cores could be broken into small sections (2-3 cm thick) after decontamination with the plastic device and ceramic knives. High-resolution depth profiles of various elements, i.e. As, Cd, Co, Cu, Ni, Pb, Zn and U, were thus attained. Concentrations in 518 ice core samples range from 0.1 (U) to 673.3 (Zn) pg g(-1).

Determination of Major Metals in Arctic Snow by Inductively Coupled Plasma Mass Spectrometry with Cold Plasma and Microconcentric Nebulization Techniques

Abstract A method was developed for the determination of K, Ca, Mg, Na, Al and Fe in Arctic snow samples by inductively coupled plasma mass spectrometry. Shield torch system under cold plasma conditions was used to overcome the spectral interferences from the plasma gas on 39K (38ArH), 40Ca (40Ar) and 56Fe (40Ar16O). Detection limits (3σ) were 1, 1, 2, 7, 6 and 3 ng/l for Na, Mg, Al, K, Ca and Fe, respectively. Reproducibility of measurements was better than 2% relative standard deviation (n=10) for all the elements of interest at 1.0 μg/l level. The sample consumption was ca. 60 μl per assay due to the use of a microconcentric nebulizer. Several Arctic snow samples were analysed and the reliability of the proposed method was confirmed by electrothermal atomic absorption spectrometry.