Ryoko Fujiyoshi

Investigation of the soil radon variation during the winter months in Sapporo, Japan.

Soil radon was measured from late October 2000 to January 2001 at three test sites on the campus of Hokkaido University in Sapporo, Japan. Factors affecting radon concentrations were investigated with relation to meteorological data, as well as soil 226Ra content, mineral composition, water content, and pH, Eh and conductivity. Soil radon varied with time and with sampling site appreciably, in a manner unaltered by the surface geology. However, the ratio of radon isotopes (220Rn/222Rn) in the soil was constant within each sampling site, regardless of varying concentration of these nuclides during the monitoring period. Snow covering on the soil surfaces may affect the 222Rn concentration.

BEHAVIOR OF RADIONUCLIDES IN THE ENVIRONMENT II. APPLICATION OF SEQUENTIAL EXTRACTION TO ZN (II) SORPTION STUDIES

Abstract Sequential extraction of a solid material (scale) collected from a water still was carried out by using the following chemical reagents; 1 M CH 3 COONH 4 , 0.04 M NH 2 OH·HCl in 25% (v/v) CH 3 COOH, 30% H 2 O 2 in dilute HNO 3 and 7 M HNO 3 . The solid residues after each extraction were collected, and then used as sorbents in a radiochemical 65 Zn(II) sorption experiment. Aqueous 65 Zn(II) was found to be predominantly associated with carbonates [and/or hydrous iron(III) oxides] and silicate minerals in the scale. Organic matter was not of primary importance in Zn(II) scavenging, probably because the organic content of the scale sample was small. Silicate lattices remaining after 7 M HNO 3 treatment did not sorb 65 Zn(II).

Behavior of radionuclides in the environment—I. Sorption of Zn(II) on clay minerals

Abstract Adsorption of Zn(II) on clay minerals (kaolinite, montmorillonite and bentonite) has been investigated spectrophotometrically and radiometrically. Both techniques offered fairly consistent results in spite that different procedure was used to obtain adsorbed amount of Zn(II). Adsorption isotherms fit Freundlich type equation depending on pH value of each clay suspension. The adsorbed amount of Zn(II) increased with increasing pH value of the suspension. Remarkable effect of Mg(II) on Zn(II) adsorption was observed in the case of bentonite. The results obtained may be explained by considering different surface properties of individual clay minerals.

Tracing depositional consequences of environmental radionuclides (137Cs and 210Pb) in Slovenian forest soils

Depth distribution profiles of environmental radionuclides (137Cs and 210Pb) have been investigated in soil to elucidate the underlying environment of semi-natural temperate deciduous and/or coniferous forest soils in Slovenia (Žirovski vrh, Idrija, Kočevski Rog, Pohorie, Gorišnica and Rakitna). Surface enrichment of both nuclides was observed at all the sites investigated in this study, suggesting that the soils had undergone little natural or anthropogenic disturbance for at least the last several decades. Apparent annual burial rates of 137Cs (0.1–0.2 cm y−−1) were estimated to be about 1.3 times higher than those of 210Pb at individual sites of different lithology, which suggests strong affinity of 210Pb to soil organic matter. Variability of the vertical distribution profiles of these nuclides depends not only on “in situ” pedology but also on geographical and meteorological conditions, especially precipitation and wind direction.

Sorption of Zn(II) on marine sediments by a sequential extraction-radiotracer technique

Abstract The sorption behavior of Zn(II) on the mineral fractions of a marine sediment collected from Sagami Bay (Japan) was investigated using a sequential extraction-radiotracer technique. The extractions used were: (i) 1 M CH3COONH4; (ii) 4 × 10−2 M NH2OHt·HCl/25% CH3COOH; (iii) 30% H2O2(pH 2); and (iv) 7 M HNO3. The residues remaining after the chemical treatment were collected, and used for the sorption experiments with 65Zn(II) as a tracer. The sorption isotherms of 65Zn(II) on all the fractions except for one with a strong acid treatment fitted a Langmuir type equation. The capacities of the individual mineral fractions for 65Zn(II) sorption were estimated from the isotherms. Treatment with 7 M HNO3 removed almost all the sorptive sites for Zn(II) ions.

Pulse radiolysis study of polystyrene-based polymers with added photoacid generators: Reaction mechanism of extreme-ultraviolet and electron-beam chemically amplified resist

The reaction mechanism of chemically amplified resist (CAR) after irradiation with ionizing radiation is important for developing extreme-ultraviolet and electron-beam lithography. The acid generation after the ionization is an essential reaction in CAR. In this study, the intermediate of the proton source of acid (a radical cation of the base polymer) in the presence of a photoacid generator (PAG) was investigated by the pulse radiolysis method. The deprotonation kinetics of the radical cation of poly(4-hydroxystyrene) (PHS) in solutions with and without PAG shows only a small difference. However, the yield of radical cations of poly(4-methoxystyrene) (PMOS) as a model of the resist with a protecting (releasing) group increases upon adding PAG. The formation of the ion pair between the PMOS radical cation and the dissociated anion with a lifetime of approximately 30 to 40 µs is suggested. The lower acid yield in PMOS than in PHS film is also discussed in terms of the stability of the radical cation.

Humic acids as a scavenger of manganese(II) and zinc(II) in soil environment using a radiotracer technique

The uptake of manganese(II) and zinc(II) by humic acids (HA) was investigated using a radiotracer technique in order to elucidate their ability of scavenging heavy metals released into the soil environment. Metal uptake by HA was affected by aqueous pH, in which the amounts of Mn(II) and Zn(II) associated with HA showed a similar pattern against pH. These facts indicate that interactions of Mn(II) and Zn(II) with HA would be ionic in character, and affected by properties of the carboxyl groups in HA.

Ligand exchange reaction of Zn(II)-acetylacetonate complex with 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid

Ligand exchange reaction of Zn(II)-acetylacetonate complex (Zn-acac2) with 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid (H2TPPS) has been investigated spectrophotometrically and radiometrically. The exchange reaction was observed by spectral change from H2TPPS to Zn-TPPS or activity of65Zn(acac)2 extracted into the chloroform phase. The 2nd order rate constants (k2) for the exchange reaction at 70 °C and at pH 7.8 were found to be 32.8±2.3 and 31.2±3.2 M−1·s−1 from the spectrometric and radiotracer experiments, respectively. For the direct complexation of Zn(II) with H2TPPS, a similar 2nd order rate constant (k=32.4±4.7 M−1·s−1) was obtained as that in the ligand exchange reaction. The activation energies (E) for the exchange and the formation of Zn-TPPS were found to be 69.3±0.2 and 69.4±0.2 kJ·mol−1, respectively, in the temperature range from 40 to 70 °C.

Deprotonation of Poly(4-hydroxystyrene) Intermediates: Pulse Radiolysis Study of Extreme Ultraviolet and Electron Beam Resist

Poly(4-hydroxystyrene) (PHS) has been used in current lithography as a backbone polymer and is also a promising material for EUV and electron beam (EB) lithography. PHS is efficiently deprotonated after the ionization of its radical cation at a low pKa ( 850 kcal/mol).

Electrochemical approach to monitoring metal exchange reaction of acetylacetonate complexes with cadmium, copper and zinc ions

Metal exchange reactions of acetylacetonate complexes with Cd(II), Cu(II) and Zn(II) ions were investigated by using cadmium and copper ion selective electrodes. Changes in the electrode potential and pH of the solutions were monitored upon adding the pertinent metal Zn(II) of the acetylacetonate (AA) complexes. In the reverse system in which a stable Cu-AA complex exists in the solution prior to adding a secondary metal ion (Cd(II) or Zn(II)), no Cu(II) was replaced by either ion. In the systems containing Cd(II) and Zn(II) as a complexed form with AA or as free ions, the exchange reactions were not explained by considering the equilibrium stability constants of the Cd-AA and Zn-AA complexes.