Search

The behavior of gaseous components of forest soil was assessed by simultaneous monitoring of 222Rn, CO2 and its carbon isotopes (δ13C, Δ14C) in soil air under a semi natural forest in northern Japan. The isotope ratio of 14C (Δ14C) in soil air CO2 was found to decrease towards late summer, suggesting gradual depletion of easily decomposed soil organic matter. There was a specific case that soil air CO2 with depleted 14C appeared suddenly under snowpack in winter. It is not always appropriate to use soil 222Rn as a tracer of CO2 efflux from the soil surface to the atmosphere.

This study examined the current distribution and downward migration of 137Cs in the humus horizon under temperate coniferous stands in the Czech Republic. Depth distribution profiles of lithogenic alkali metals (K, Rb, and Cs) were also traced to find any indication regarding the 137Cs dynamics within the humus horizon. Soil (bulk soil) samples were collected manually from the uppermost down to a depth of 20 cm at three points situated 10–20 m apart in three locations diversely affected by the Chernobyl accident in 1986. Humus samples (about 6 cm in thickness) were separately collected at three points adjacent to the bulk soil sampling. The humus samples were divided into three fractions (upper, middle, and lower) denoted to Hu, Hm, and Hl, respectively, depending on their depths. Activity concentration of 137Cs and the amount of alkali metals (K, Rb, and Cs) in each humus fraction were determined with gamma spectrometry and ICP spectrometry, respectively. Some properties (pH, density, SOM, and identification of clay minerals), of both bulk soils and humus horizons were also investigated. The highest activity concentration of 137Cs (Bq kg−1) appeared in the upper portion of the soil (mainly humus horizon) under three coniferous stands about 30 years after the Chernobyl accident. Increasing activity of 137Cs (Bq) was found in the lower humus fraction (Hl, 4~6-cm depth range) with no appreciable amounts of clay minerals like illite and smectite in the investigated sites. The findings suggest that the fallout 137Cs moves downward at a speed of 0.13~0.19 cm year−1 with degrading organic matter within the humus horizon. Possible association of 137Cs with alkali metals (K, Rb, and Cs) was suggested by depth distribution profiles of lithogenic alkali metals (K, Rb, and Cs) in humus. The humus horizon under temperate coniferous stands plays an important role in retaining fallout 137Cs for a long time. Comparing the depth distributions of the fallout radionuclide 137Cs with the depth distributions of lithogenic alkali metals (K, Rb, and Cs) gives valuable information for clarifying mechanism of 137Cs movement in humus. Further investigation is needed to elucidate mechanism of 137Cs migration within humus horizon by tracing 137Cs speciation and decomposing soil organic matter simultaneously.

Distribution of the 137Cs activity concentrations, soil pH, content of organic matter and composition of mineral portion in humus were investigated in forest soils variably loaded by Chernobyl-derived fallout. Maximum in the 137Cs activity concentrations were found in the uppermost organic soil horizons. In forest humus the 137Cs activity concentrations was negatively related to pH and the content of organic matter. No significant content of clay minerals was detected in humus. Slow vertical migration (0.04–0.06 cm year−1) and effective half-life of 137Cs in humus about 20 years was found. The initial surface 137Cs activities in 1986 were estimated.

Simultaneous monitoring of soil 222Rn and soil moisture at different depths (0.3, 0.6, 1.0 m) has been conducted from May 28, 2014 to March 31, 2015 in a loamy soil under a temperate deciduous stand in Fukushima prefecture, Japan. Atmospheric precipitation higher than 0.9 mm h−1 in intensity and longer than 19 h in duration significantly reduced soil 222Rn levels at all the three soil depths. Movements of soil water and 222Rn in soil air were analyzed with sets of field data resulting in the same order of magnitude in diffusivity (0.5–7.0) × 10−6 m2 s−1 for moisture and (0.9–6.0) × 10−6 m2 s−1 for soil 222Rn. Applying “in situ” monitoring of soil 222Rn at several different soil depths could be a useful way to analyze soil water dynamics usually difficult to be evaluated.

Pulse radiolysis of highly concentrated poly(4-hydroxystyrene) (PHS) solutions in cyclohexanone and p -dioxane was performed both with and without an onium-type photoacid generator (PAG). With increasing PHS concentration, the rate constant of deprotonation of PHS radical cations was found to decrease. In the presence of PAG, the yield of the multimer radical cation of PHS was shown to decrease. We found that pairing between the anions produced by the attachment of dissociative electrons of PAGs and the monomer PHS radical cations restrict local molecular motions, leading to the formation of the multimer PHS radical cations.

Specific activity of 210Pb (210Pb/Pb) is a good indicator for distinguishing local and remote emission sources of Pb deposited on some forest floors in Slovenia. Another parameter (zinc in soil) gives additional information on possible emission sources and distance of Pb transported from the source. The procedure based on 210Pb activity measurements and non-destructive Pb and Zn determination is rather simple, and not necessary any chemical pre-treatments with strong acids. The soils investigated in this study were collected from several temperate forest sites (Žirovski Vrh, Idrija, Kocevski Rog, Pohorje, Gorisnica, Rakitna, Hotavlje, Otovci, Ptujska gora and Puce) in Slovenia where high level of Pb contamination has been known in some places. Regression analyses of the results suggest an applicability of the proposed procedure for estimating emission sources and atmospheric transportation of Pb.

Fluorination of resist materials is an effective method used to enhance the energy deposition of extreme ultraviolet (EUV) light in the fabrication of next-generation semiconductor devices. The dynamics of radical ions are important to understand when considering the radiation-chemistry of the resist materials using EUV and electron beam lithography. Here, the dynamics of the radical anions and cations of benzenes with one or two 2-hydroxyhexafluoroisopropyl groups (HFABs) were studied using radiolysis techniques. The formation of dimer radical cations was observed only in the monosubstituted benzene solutions of 1,2-dichloroethane. If the compound contained more than two substituents, it was found to hinder the necessary π-π overlapping. Pulse radiolysis of HFABs in tetrahydrofuran showed a characteristic spectral shift of the radical anion within the region of several hundred nanoseconds. From the results of low-temperature spectroscopy and density functional calculations, it is suggested that excess electrons of the 2-hydroxyhexafluoroisopropyl group of the radical anions cause dissociation into neutral radicals.

Soil radon (222Rn) has been monitored since August 2013 at three different soil depths on a campus forest of Fukushima University in Japan, where a large amount of fallout nuclides were released by the accident of Fukushima Daiichi Nuclear Power Plant in March 2011. The primary purpose of this study is to evaluate 222Rn activity level, variability and factors controlling 222Rn concentration in soil air using data obtained from August to December 2013. Time series of 222Rn activity concentration showed depth-dependent variability with an equilibrium value (222Rneq) during this observation period; 7.5, 14 and 23 kBq m−3 at 0.3, 0.6 and 1.0 m in depth, respectively. Two typhoons passing over the site had a great influence on soil radon level, which was practically used for evaluating effective diffusion coefficient of 222Rn. Transport mechanism of 222Rn in soil air was considered to be diffusion-controlled with data sets on changing 222Rn concentration with time in selected cases that showed decreasing (or increasing) 222Rn concentration with time at every depth. Important factors affecting soil 222Rn variability are meteorological parameters, low-pressure front passing over the site, and subsequent precipitation. Time lags of decreasing 222Rn concentration at different depths after rain indicate a certain relationship of 222Rn level with moving water (and water vapor) in soil. The findings obtained in this study are important to evaluate the fate of fallout nuclides (radiocesium) in contaminated forest sites using soil radon as a tracer of moving soil air.

Radiopotassium isotopic composition (40K/K, %) of several forest soils did not show a constant value of generally known 1.17 × 10−2 %, but they were varied significantly from 0.4 × 10−2 to 1.3 × 10−2 % at different locations under different environmental conditions. Surface portion of a soil (2–4 cm in depth) gave always lower 40K/K values compared with those of deeper soil layer (35–40 cm in depth). Ion exchange of K+ with NH4 + did not affects the 40K/K value in any soils, which revealed with chemical leaching experiments in the laboratory. Some plant species showed much lower 40K/K values than those in the surface soil. Possible reasons for varying 40K/K values obtained in this study may result from a dynamic behavior of potassium in soil, probably due to biological activity including root uptake and decomposing soil organic matter by microorganisms in the forest floor.

Soil radon (Rn-222) has been monitored during winter months under cool-temperate deciduous stands of different surface geology in Tomakomai and in Sapporo, Hokkaido, Japan. Radon level was lower in Tomakomai of immature soil of porous volcanic ash emitted from an active volcano (Mt. Tarumae), compared with those in Sapporo of alluvial sediments. In Tomakomai, mean value of the Rn-222 activity concentration was higher in winter (570 Bq m(-3)) than in summer (350 Bq m(-3)) at a depth of 1 m, which is consistent with the results in cold and dry winter reported in the literature. In contrast, soil radon decreasing with decreasing soil temperature from mid-September (5.0 kBq m(-3)) remained low (2.6 kBq m(-3)) under persistent snow in Sapporo, which had already been observed in the same location. Measurements of the activity concentrations of Rn-222 in snow and in snow air as well as in soil air indicate that the small amount of Rn-222 is released from the ground surface to the overlying snowpack with a Rn-222 flux density of 0.4 mBq m(-2) s(-1) under thick snow cover in Sapporo.

Carbon sources were estimated by measuring carbon isotope ratios (δ13C and Δ14C) with accelerator mass spectrometry (AMS) in forest soils of different lithology. Six locations were selected in temperate deciduous and coniferous stands in Slovenia (Žirovski vrh, Idrija, Kocevski Rog, Pohorje, Gorisnica, and Rakitna), where carbonate rocks consisting of limestone and dolomite are abundant as underlying bedrock. Carbon isotope fractionation would not have occurred in two carbonaceous soils, since the values of both δ13C and Δ14C changed consistently in these soils after thermal (550°C, 2 h) or chemical (1 M HCl, 24 h) treatments. Organic components were found to be predominant carbon sources (70–100%) in the uppermost portions (0–2 cm in depth). In deeper portions at a depth of about 30–35 cm, soil carbon may be derived completely from underlying carbonate minerals in Idria, western part of Slovenia. The Combination of heat and chemical treatments with AMS provides practical information on soil carbon sources in carbonaceous soils.

Depth profiles potassium and its isotope ratio (40K/K) were investigated in several forest soils from different geological and climatic backgrounds. The ratio was found not to be constant (0.0117%) but varied appreciably from 0.0085% to 0.0167% among different soils. Possible factors affecting variability of 40K/K values were considered by a multivariate factor analysis which suggested that aqueous parameters like humidity and pH might be a controlling factor in the surface soils. The amount (and probably chemical forms) of iron oxide may be another one influencing 40K/K values in mineral components at deeper portions.

Radon ((222)Rn) and carbon dioxide were monitored simultaneously in soil air under a cool-temperate deciduous stand on the campus of Hokkaido University, Sapporo, Japan. Both (222)Rn and CO(2) concentrations in soil air varied with atmospheric (soil) temperature in three seasons, except for winter when the temperature in soil air remained constant at 2-3 degrees C at depth of 80 cm. In winter, the gaseous components were influenced by low-pressure region passing through the observation site when the ground surface was covered with snow of ~1 m thickness. Carbon isotopic analyses of CO(2) suggested that CO(2) in soil air may result from mixing of atmospheric air and soil components of different origins, i.e. CO(2) from contemporary soil organic matter and old carbon from deeper source, to varying degrees, depending on seasonal meteorological and thus biological conditions.

Global carbon estimates have identified abiotic CO2 as a potentially significant source of atmospheric CO2, albeit little is known about its origin. The aim of this study was to identify the origin of soil CO2 using carbon isotopes and 222Rn data. The study involved collecting data from seven Slovenian forest soils developed over bedrock with contrasting geology where different origin of soil CO2 was expected; two sampling sites were located on soils formed above carbonate bedrock, one above metamorphic bedrock and the remainder above clastic sedimentary rocks. Analysis of soil gas including the levels of CO2, carbon isotope measurements (12C, 13C and 14C) and 222Rn activity was recorded at a soil depth of 80 cm. Isotopic analysis revealed that the CO2 was young and there was no difference in the age of soil CO2 above either carbonate or non-carbonate bedrock. The data also suggest that the 13C-enrichment in soil CO2, above carbonate bedrock was a consequence of the mixing of soil CO2 with atmospheric CO2 and/or the ventilation of subterranean CO2 from pores, fissures and cavities. The latter effect was supported by the high 222Rn concentrations observed at these sites. Based on the $$\delta^{13} {\text{C}}_{{{\text{CO}}_{2} }}$$ data, photosynthesis prevailed over microbial respiration accounting for the majority (>70 %) of total soil CO2 over non-carbonate bedrock—at least at the time of sampling. Overall, results from this study could represent useful information for global carbon cycle models used to predict the impacts of climate changes.

We evaluated the migration of radionuclides (131I, 129I, 134Cs, 136Cs, 137Cs, and 132Te) in the surface soil after the Fukushima nuclear accident. The radionuclides in the soil collected late March in 2011 were barely leached with ultrapure water, indicating that these are insoluble. We observed the chemical behavior of 137Cs and 129I in soil: (1) 137Cs was predominantly adsorbed within a depth of 2.5 cm from the ground surface; (2) 137Cs was hardly released from soil by the water leaching experiments that lasted for 270 days; (3) approximately, more than 90 % of 137Cs was adsorbed on organic matters and the residual fractions, while 129I was mainly fixed on the Fe-Mn oxide and organically bounded fraction. Therefore, we conclude that 137Cs and 129I in soil seldom leach into the soil water and migrate downward because of the irreversible adsorption. The shallow groundwater which residence time is short.

Dimethylsulfoxide (DMSO)–Br complexes were generated by pulse radiolysis of DMSO/bromomethane mixtures and the formation mechanism and spectral characteristics of the formed complexes were investigated in detail. The rate constant for the reaction of bromine atoms with DMSO and the extinction coefficient of the complex were obtained to be 4.6×10 9 M −1 s −1 and 6300 M −1 cm −1 at the absorption maximum of 430 nm. Rate constants for the reaction of bromine atoms with a series of alcohols were determined in CBrCl 3 solutions applying a competitive kinetic method using the DMSO–Br complex as the reference system. The obtained rate constants were ∼10 8 M −1 s −1 , one or two orders larger than those reported for highly polar solvents. Rate constants of DMSO–Br complexes with alcohols were determined to be ∼ 10 7 M −1 s −1 . A comparison of the reactivities of Br atoms and DMSO–Br complexes with those of chlorine atoms and chlorine atom complexes which are ascribed to hydrogen abstracting reactants strongly indicates that hydrogen abstraction from alcohols is not the rate determining step in the case of Br atoms and DMSO–Br complexes.

To realize extreme ultraviolet (EUV) lithography for mass production of semiconductor devices, enhancements of performance of chemically amplified resist have been still important issue. In EUV resist, radiation chemical reactions occur after irradiations of the EUV light. Dynamics of chemical intermediates of EUV resist after exposure to the ionizing radiations is important for understanding new resist design. Fluorinated resists have been developed for ArF, F2, and EUV lithography. Fluorinated polymers are effective to enhance the sensitivity of the EUV resist because F atom has higher absorptivity of EUV photons. However, the fluorination effect on the radiation chemical reactions in the resist has not been clarified in detail. In this study, we investigated the dynamics of radical ions of fluorinated polymers (FPs) by pulse radiolysis method and quantum chemical calculations to clarify the reaction mechanism for EUV lithography.

Continuous 222Rn monitoring in soil gas since November 22, 2004 has revealed variability in activity concentration with time in the semi-natural woods on the campus of Hokkaido University in Sapporo, Japan. Among various factors affecting soil radon levels and variability, temperature was found to be dominant during three seasons when activity concentrations of 222Rn showed a diurnal high and nocturnal low with a boundary around 10 o'clock in the morning. This pattern was disturbed by low pressure fronts with occasional rain. The activity gradually decreased as soil temperatures decreased from late November to mid-December. After the ground surface was completely covered with snow, soil radon levels became low with a small fluctuation. There were several peaks of 222Rn on the time-series chart in winter. Those peaks appearing in early winter and early spring may be interpreted by considering meteorological parameters. In a few cases, the radon activity suddenly increased with increasing pressure in the soil at a depth of 10 cm, which may be associated with subsurface events such as seismic activity in the area.

Photolysis of complexes of dimethyl sulfoxide (DMSO) with chlorine atoms results in rapid and permanent photobleaching which may be due to intramolecular hydrogen abstraction. The effects of solvent polarity were examined in a wide variety of DMSO–carbon tetrachloride mixed solvents. The quantum yields of photobleaching decreased from 0.27 to 0.08 as the solvent polarity increased, while significant changes were observed in the low DMSO concentration range (

Complexes of chlorine atoms and carbon disulfide (CS2) were produced by pulse radiolysis of CS2 in halocarbons and photochemical reactions were studied by laser flash photolysis. Excitation of CS2/Cl complexes resulted in rapid and permanent photobleaching. The photobleaching of CS2/Cl complexes is due to intermolecular chlorine atom abstraction in CCl4 with a quantum yield of 0.04, while that ascribed to hydrogen atom abstraction in 1,2-dichloroethane has a quantum yield of 0.21. The effects of additives are discussed based on the bond dissociation energy.

Several factors controlling the soil radon level in the present site were found to be changing air-filled porosity caused by fluctuations in moisture content, differences between the atmospheric and soil temperatures as well as volumetric (226)Ra content of the soil. The radon activity increased significantly in early October, especially at point 1, possibly as a result of a magnitude 8.0 earthquake which occurred on September 26, 2003, with epicenter located offshore near Tokachi, Hokkaido.

The reactivity and selectivity of carbon disulfide-chlorine atom complex (CS2/Cl) for hydrogen atom abstraction from various alcohols were studied by pulse radiolysis technique in carbon tetrachloride at room temperature. The measured absolute rate constants were in the range from 4.0×106 for methanol to 3.5×107 dm3 mol−1 s−1 for cyclopentanol. The hydrogen abstraction selectivity was calculated based on the analysis of partial reactivities. The tertiary/primary selectivities were determined to be 8.2 for α -position and 6.8 for β -position of alcohols.

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.

The sorption of manganese(II) and zinc(II) on soil samples collected from Sapporo (Japan) and Tiksi (Russia) was investigated using a radiotracer technique to elucidate the abilities of soil organic matter as a scavenger of heavy metals released to the soil environment. The sorbed amounts of both manganese and zinc metals to organic soil components were estimated to be different on different soils, depending on the pH of aqueous phase. The degree of humification of pertinent soils was suggested as a parameter which could describe the properties of the organic soil matter in complexing with heavy metals.

Migration process of 137Cs in soil has been investigated by measuring its activity concentration with depth. However, surface portion of soil (organic components) have various properties with different thickness. It is necessary to classify the distribution of 137Cs into each forest component. Therefore, we investigated forest components (litter, fermentation, humus, Ah horizon, upper and lower part of mineral soil) in several forest areas of the Czech Republic, and tried to clarify the present situation about 30 years after the Chernobyl accident. The highest value of 137Cs activity concentration was obtained to be 1.60 kBq/kg in fermentation. Cesium-137 is therefore still present in organic layer. We’ve got previous results on distribution of 137Cs in humus horizon at the same forest area. Apparent half-life of 137Cs in humus horizon was estimated to be 20.2 year. This value gave initial deposition of 137Cs in humus layer to be 3.9 kBq/kg, comparable with that (4.3 kBq/kg) derived from the apparent burial rate of 137Cs. This is a new finding on initial deposition of 137Cs in humus layer with different ways. In order to predict future situation in forest components affected by nuclear accidents, long term monitoring is found to be important.

Poly(4-hydroxystyrene) (PHS), a backbone polymer in resist constituents is also a promising material for extreme ultraviolet (EUV) and electron beam (EB) lithography. Efficient deprotonation occurs from radical cations of irradiated PHS. A hydroxystyrene unit is incorporated in the chemically amplified resist structure as a proton source, in which reaction mechanism has not been well established. In this study, deprotonation mechanism of an ionized PHS was characterized by using pulse radiolysis techniques. The influence of several additives such as sulfoxides and amides with high acidity on the kinetics of the deprotonation was investigated to clarify the fundamentals of the enhancement of deprotonation efficiency from the PHS radical cation. Influence of the additives on the acid yield in thin film was also investigated.

Chemically amplified resists have been widely used in the mass production line. An acid generation mechanism induced by ionizing radiation with extreme ultraviolet (EUV) and electron beam is an important issue for improvement of the resist performance such as sensitivity, roughness, and resolution below 16 nm. However, the details of deprotonation kinetics from the ionized resist solid film immediately after the ionization have been still unclear. In this study, pulse radiolysis of highly concentrated poly(4-hydroxystylene) (PHS) solutions was performed. The viscosity dependence on the deprotonation dynamics of the ionized concentrated solutions was investigated to clarify the proton generation of ionized PHS in a medium with low mobility. The deprotonation from the PHS radical cation becomes slower with increasing PHS concentration. It is suggested that the deprotonation reaction is slower in a less mobile medium because of decrease of the molecular motions.

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.

Uptake of manganese(II) and zinc(II) by chlorophylla (Chl) was investigated using a radiotracer technique in order to elucidate its ability of scavenging metals released into the soil environment. Two possibilities were considered for the metal uptake: (1) substitutional complexation with Chl and (2) inclusion of the metals into Chl aggregates. It was found that manganese(II) was not trapped appreciably by both Chl itself and its aggregates. Magnesium of Chl was exchanged with zinc(II) in aqueous phase giving Zn−Chl at pH values higher than 7. Zinc(II) was found to be trapped by Chl aggregates depending on the pH of the aqueous phase.

Radiometric sorption experiments were carried out on surface soil samples collected from several sites around Sapporo city (Hokkaido, Japan) in order to evaluate their capacities for the sorption of Zn(II). The maximum sorption (Am) of Zn(II), obtained from the sorption isotherm, was only 2–5% of the cation exchange capacity (CEC). The Am values were correlated with the pH of the soil suspensions, which indicates that zinc sorption would occur competitively with protons in the suspension. The effect of organic matter on the Zn(II) uptake was estimated from the Am change of the individual samples before and after heat treatment. Coordinate uptake of the Zn(II) into the degrading organic matrices was believed not to be important for Zn(II) sorption in some of the present soil samples.

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.

Traces of short- and long-lived fallout 134Cs and 137Cs were found in surface soil (volcanic ash soil) under a cool-temperate deciduous stand at Tomakomai Experimental Forest in Hokkaido, Japan after the Fukushima nuclear accident in March 2011. Most of them were present in the uppermost 5–6 cm of the soil. Mean concentrations of 134Cs and 137Cs were found to be 2.4 (±0.3) and 89 (±2) Bq Kg−1 in May, and 6.9 (±0.4) and 94 (±2) Bq Kg−1 in November 2011, respectively. A small increase in radiocesium concentration may result from biological activity in the uppermost portion of the soil in which fallout nuclides derived from the Fukushima NPP would not have existed in May. They were supposed to be fallen down on the fresh litter layer in the previous year. The results of a sequential extraction experiment with 1 M CH3COONH4 solution showed that desorption of radiocesium from the soil was difficult and not simple ion exchange processes.

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.

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 (k 2) 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.

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).

The influence of degree of copolymerization of poly(styrene-ran-methyl methacrylate) [P(S-MMA)] on the deprotonation mechanism for EUV chemically amplified resists were investigated by pulse radiolysis, quantity of the acid yield, and density functional theory methods. The degradation of MMA unit occurs immediately before the hole transfer to the styrene unit in P(S-MMA) in the low PS mole fraction (< 50 %). The hole transfer from MMA unit to styrene units occurred in the high PS mole fraction (> 70 %). It is assumed that the formation of styrene multimer (n > 3) causes the hole transfer.

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.

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.

A metal exchange reaction between*Zn-EDTA and Mn-PAN complexes has been investigated to evaluate the possibility of Mn determination in geological samples radiometrically. Exchange ratios (E) of Mn(II) to Zn(II) were obtained from measuring the activity of65ZnPAN2 extracted into an organic phase. Values of E increased rapidly with increasing pH of the aqueous solution. Suitable conditions for the determination of Mn(II) in soil samples are considered.

Environmental radionuclides (K-40, Cs-137, Pb-210, Ra-226) were determined in soils under semi-arid stands, a transition area from thorn to deciduous forest in El Angolo, and heath stands in the Alto Mayo in Northern Peru in order to elucidate their activity level in soil, and to trace underground environment in remote areas of little anthropogenic intervention. Anthropogenic Cs-137 was only found in the uppermost portion of the soils in small amount, whereas the Pb-210 activity was exceptionally high at the soil surfaces in a tropical stand of Alto Mayo. The results suggest a fallout nuclide, Pb-210, having been transported from local source(s) not to be specified yet. [References: 18]

The fluorination of a chemically amplified resist is an effective method for use in EUV lithography. However, it has been suggested that the fluorination of the base polymer of the chemically amplified resist induces the electron scavenging reaction by the base polymer and reduces the acid yield. In this study, we clarified the formation of transient species and the acid yields of fluorinated polymers after exposure to the ionizing radiations. The acid yields of fluorinated polymers with hydroxyl groups were lower than that of poly(4-hydroxystyrene) (PHS). The lower acid generation efficiency in fluorinated polymers was due to not only the reaction between fluorinated polymers and electrons but also the lower deprotonation efficiency of the radical cation of the fluorinated polymer.

Vertical profiles of environmental radionuclides (40K, 226Ra, 210Pb and 137Cs) were investigated in several temperate forest soils in Germany to estimate heterogeneity of the soil horizon of interest. Absolute values of the activity concentrations of these nuclides varied to a large extent depending on the properties of individual forests as well as local geology. Several trends were generally observed independent of the location: (1) Activity concentrations of 40K increased with increasing soil density reflecting that most potassium is contained in mineral components of the soil. The variations in the 40K activity with depth may relate to biological activities in subsoil, such as root uptake of the nutrients. (2) Profiles of 226Ra with depth could be an indicator for evaluating soil heterogeneity within a horizon of interest. They are also useful to estimate anthropogenic 210Pb (210Pbexc) derived from the atmosphere via dry fallout or wet deposition. In several forests, there appeared surface enrichment of 210Pb down to a depth of approximately 10 cm, in which the 210Pb would have come from the atmosphere by combustion of fossil fuels. (3) Depth profiles of 137Cs were roughly divided into three types in which (a) the activity concentration decreased exponentially with soil depth, (b) small amounts of 137Cs existed only in the upper-most layer of the soil (0–5 cm) and (c) 137Cs disappeared at certain depths and appeared again at deeper portions of the soil. Consequences of bioturbation could be deduced from variability in vertical profiles of the environmental radionuclides. It is probable that a site showing an exponential decrease of the 137Cs activity with depth and also having a surface enrichment of 210Pb is not significantly influenced by bioturbation.

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.

DMSO–Cl complexes were produced by pulse radiolysis of mixtures of dimethyl sulfoxide (DMSO) and CCl4 of various compositions, and photochemical reactions were studied by laser flash photolysis. Th...

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 pK a (850 kcal/mol).

A sequential extraction-radiotracer technique was applied to a sediment core sample collected from lake Biwa (Japan) in order to evaluate relative importance of the fractionated solid components to sorb Zn(II) ions. The core was previously divided into three parts from the surface of the sediment; upper (0–6 cm), middle (6–12 cm) and bottom (12–18 cm). The solid residue after each chemical treatment was collected to perform a sorption experiment by using 65 Zn as a tracer. A difference in the amount of Zn(II) sorption was observed among original samples without any chemical treatments at each depth. The amounts were very small (10 −5 −10 −4 mol Zn(II) 100 g −1 of dry sample) in all fractions of the sediment. Electrochemical measurements of cadmium and copper ion sorption supported the results from the radiometric sorption experiment. The effects of several potential factors on zinc sorption were investigated. Ion exchange of zinc with protons on the mineral surfaces was a significant cause of the zinc sorption.

Extreme-ultraviolet free-electron lasers (EUVFELs) producing intense femtosecond pulse are able to superimpose ion-pair formation induced by a single photon onto the other in the resist polymer degradation. Electron beam resist (ZEP520A) sensitivity was obtained by using 61 nm EUVFEL at different dose densities in order to observe the multiple spur effect in a well-controlled environment. A higher ionization density has been identified to suppress the resist-degradation effectiveness due to the multiple spur effect for the first time. This is explained by two competing effects, namely, spatiotemporal overlap reducing the effectiveness, and high radical concentration enhancing cross-linking efficiency.

The dependence of the degree of copolymerization on the dynamics of radical cations of resist polymers was studied. The dynamics of radical cations was investigated in a chemically amplified resist polymer system. In this study, poly(styrene-ran-methyl methacrylate) [P(S–MMA)] was used as the base polymer of the resist model compound. It is suggested that radical cations of MMA are predominantly decomposed to be deprotonated immediately before the hole transfer to the styrene unit in P(S–MMA) at a lower styrene mole fraction (70%). It is thus suggested that the hole transfer from the MMA to the multiple styrene units (n > 3) occurs in P(S–MMA).