Narrow Results

During the examination of the representative specimens, a barite ore and a polymetallic chimney, from the JADE hydrothermal field of Okinawa Trough, many amorphous silica globules of approximately 10 to 50 micrometers in diameter were found as isolated sphere or bunchy aggregation. We performed micro-PIXE analyses of the globules to check the effectiveness of the method to such soft and vulnerable material, and to understand the geochemical characteristics. The result shows that amorphous silica can include various kinds of elements in lithophile, chalcophile and siderophile categories. The trace element distribution of the globules indicates that amorphous silica could be a good monitor of geochemical environment; and implies that the chemical variation of ore often found in a mineral field is mainly derived by change in local physicochemical conditions of single mineralizing fluid rather than multiple injection of the solution.

An external scanning ion microbeam system has been developed for in-air micro-PIXE analysis at JAERI Takasaki. The analysis system is widely used for various researches in recent years. The system consists of the external scanning ion microbeam system, a multi-parameter data acquisition system, a file transfer protocol (FTP) server and analysis software. The software of the system provides a graphical user interface for interaction between users and an experimental setup. The server is connected to the Internet and allows remote users to access the experimental data.

Micro-PIXE and inductively coupled plasma mass spectrometry (ICP-MS) were applied to elemental distribution analyses in plant root apex which is composed of various types of tissues and cells in different developmental stages. ICP-MS was so sensitive that a large number of elements including Na, Mg, P, S, K, Ca, Mn, Fe, Cu, Zn, Se, Rb, Sr and Cs could be determined quantitatively. These fourteen elements included almost all the essential elements for plant growth. Only a rough estimation, however, could be obtained by ICP-MS for the elemental distribution at the tissue level, by analyzing sections from the root apex. On the other hand, micro-PIXE was effective for detailed mappings of elemental distributions. The images of elemental distributions were obtained for Na, Mg, P, S, K, Ca, Mn, Fe and Zn, corresponding to the microscopic images of the root structures. The localizations of P, K and Zn in some tissues were observed by the mappings. These results indicated that micro-PIXE and ICP-MS have different, but complementary abilities for the investigation of elemental distributions in plant tissues.

Micro-beam scanning PIXE and scanning transmission ion microscopy (STIM) were applied to measurement of Siebold's beech (Fagus crenata Blume) leaves. The beech leaf samples were collected from selected beech trees at Tsugaru Pass near the Shirakami-Sanchi World Heritage Area, in the 1999 growing season. We focused our interest on the influence of the atmospheric environment (acidic deposition, aerosol and gaseous substances, etc.) on the forest ecosystem. Our approach to real images of the deposition of airborne particulate on leaves led to the elucidation of the process of elemental absorption from air and plant metabolism. As a result, it is suggested that 1) overlapping STIM images and elemental maps demonstrate the patterns of the elemental absorption into plants, 2) comparison of the elemental maps of leaves taken at the different growth stages may provide useful clues to the elemental accumulation mechanism in leaves, and 3) silicon distribution in leaves is indicative of airborne particulate deposition on them.

Micro-beam scanning PIXE (micro-PIXE) and scanning transmission ion microscopy (STIM) were applied to measurement of one-year-old seedling root from a Siebold's beech (Fagus crenata Blume) tree. The beech seedling root samples were collected at the centerpiece of the Shirakami-Sanchi World Heritage Area during October 2001. Target samples for micro-PIXE and STIM analyses were transverse sections from tip, midpoint and root of the beech seedling root. We focused shedding light on tree root metabolism, and are to get a real image about the elemental distribution in the tree root. STIM images were similar to those generated using stereomicroscope and/or transmission microscopy. Real images in the form of elemental maps were obtained for nine elements: Na, Mg, Al, Si, P, S, Cl, K and Ca. Of these, typical elemental maps were Si and Ca, which were both concentrated in the epidermis. Si was prominent in the tip, while Ca was prominent in the root.

Rat basophilic leukaemia cells (RBL-2H3) were analyzed by in air micro-PIXE analysis to investigate the relationship between the distribution of elements and histamine release in immune system. RBL-2H3 cells were sensitized with monoclonal immunoglobuline E(IgE) and stimulated with antigen. In the stimulated cells, it is understood that the level of Ca²⁺ increases in cytoplasm and then the degranulation or the release of chemical mediators occur. In this study, stimulated RBL-2H3 cells with antigen and control cells were analyzed. After the stimulation, the Na in the cells was increased. Moreover some stimulated cells showed the characteristic distribution of sulfur that is not accompany with the distribution of phosphorus. In the same measurement, the aggregations of Na, Ca, Fe, and Zn were observed.

In anoxic marine sediments sulfur is considered to be essential to the formation of humic substances. It is also estimated that sulfur may play a crucial role in the degradation of wood buried in marine sediments. In order to confirm this prediction, we observed the tissue of fossil wood from the marine clay aged 1.1 million years by polarizing microscopy and SEM before the determination of its sulfur content by PIXE and EDXA, and its distribution by μ-PIXE. Results show that the sample contained about 6000 μg/g of total sulfur and tracheid cells with birefringence, which have probably preserved the original wood components contain less sulfur compared to those without birefringence, which are heavily degraded. This might suggest the participation of sulfur in the degradation or the formation of humic substances occurred in wood tissue during diagenesis.

In this study we compared the structure and trace elements contents of three kinds of hair samples from Mexican infants: pre-Columbian mummies, mummies from the relatively recent past (less than 200 years) and from a healthy living 6-year old boy. External and internal morphology was characterized by electron microscopy. Trace elements were determined by PIXE (broad proton beam and microprobe method). The three groups showed differences in structure and elemental content. Calcium-containing mineral inclusions were observed in mummy hair but not in modern hair. Also, a progressive enrichment with age was observed for elements such as Ca, Fe, Mn, and Pb, indicating a postmortem incorporation. Other elements, such as Zn, Cu and Sr, less affected by post-mortem processes, were present at very similar levels, but still in a higher proportion relative to modern hair, preventing any possible relation to the individual's health.

The prostate is an accessory sex organ that secretes essential components of semen. High levels of Zn are found both in the prostate and its secretion. In the present study, the effects of environmental stress on zinc levels in the prostate were examined in Wistar male rats exposed to tributyltin chloride (TBTC), an environmental toxicant, by inductively coupled argon plasma–mass spectrometry (ICP-MS) for determination of Zn concentration in lobe-dissectioned specimens and micro-PIXE analysis for determination of site-specific distribution of Zn in prostatic sections. A single oral administration of TBTC to rats at a dose of 90 μmol/kg resulted 14 days later in a decrease in the Zn level in the dorsolateral prostate but not the ventral prostate. The TBTC did not affect the weight of the prostate tissue. Micro-PIXE imaging found Zn both in the lumen and the epithelium of the lateral prostatic tubules. PIXE spot analysis revealed that the epithelium of the control rat contained levels of Zn 4–fold higher than in the lumen and that Zn in the epithelium decreased selectively after TBTC exposure.

Sakhalin taimen, Hucho perryi, is one of the largest freshwater fish in Japan, where it is close to extinction because of indiscriminate fishing, water pollution, and river construction. Interpretable ecological information about the species, however, is scarce. We examined the migration history of H. perryi by analysis of strontium (Sr) content in fish scales using inductively coupled plasma mass spectrometry and Sr distributions associated with ridges (growth lines) in the scales, with micro-beam scanning PIXE (micro-PIXE) analyses. Sr levels in the scales of H. perryi collected along the Sarufutsu coast were higher than those of salmonid collected at Shumarinai, a freshwater lake. Micro-PIXE line analyses showed that the scale Sr values of the Shumarinai Lake samples remained consistently low from the edge toward the core of the scales. The Sr values from the Sarufutsu coast samples remained relatively high from the edge toward the core; Sr levels from second to fourth position from the edge were about ten times higher than the mean levels of Shumarinai Lake samples. These results suggested that H. perryi from the Sarufutsu Coast had experienced the marine environment.

Elemental distributions of Al, Si, P, S, K, Ca in tea leaves were measured using micro-beam PIXE. In mature tea leaf, aluminum localized eccentrically in the upper epidermis and silicon showed quite similar spatial distribution. It was found that the aluminum concentration and spatial distribution changeed with the growth period of the tea leaf. In younger leaves of two and four month, aluminum showed relatively low concentration compared with the matured one and distributed in mesophyll cell uniformly. In five month leaf, aluminum concentration became higher and the distribution began to localize in upper surface

In this paper, we have developed a wavelength dispersive X-ray spectrometer microparticle-induced X-ray emission (WDX-$\mu$-PIXE) system combining a microbeam system with high spatial resolution and wavelength dispersive X-ray (WDX) spectrometry with high-energy resolution for chemical state mapping. A Von Hamos geometry was used for the WDX system to achieve higher detection efficiency and energy resolution. The system consists of a curved crystal and a CCD camera. The WDX system was installed in a newly developed microbeam system. The energy resolution of the WDX system was 0.67 eV for $\text{Si-}{K}_{\alpha 1}$ (1740 eV). $\text{Si-}{K}_{\alpha 1,2}$ and $\text{Si-}{K}_{\beta }$ X-ray spectra from various Si compounds were measured and chemical shifts related to chemical states were clearly observed. The system was applied to the chemical state analysis of clay particles. After elemental mapping of the clay particles using a conventional $\mu$-PIXE system with a Si(Li) detector, particles to be analyzed were selected and analyzed sequentially with the WDX system. $\text{Si-}{K}_{\beta }$ spectra from clay particles were obtained. The microscopic spatial distribution of elements and chemical state of the clay particles were sequentially measured with high energy and spatial resolution using a microbeam.

In this paper, we developed a technique for analyzing individual PM_2.5 particles using micro-PIXE. PM_2.5, a designation for extremely small particulate matter (PM) in the air, has recently become the center of attention because high levels of PM_2.5 were recorded in parts of western Japan, especially Fukuoka Prefecture, in January 2013. For a better understanding of their formation mechanism, analysis of individual particles is indispensable. We collected PM_2.5 on a $4\mu \text{m}$ thick Prolene foil using a multi-nozzle cascade impactor at Fukuoka Women’s University, Fukuoka, Japan. Its elemental analysis was carried out using a micro-PIXE system at Tohoku University. Although elemental concentration ratios of scanned areas were similar, those of individual particles were quite different from each other. Elemental concentration ratios for individual particles were categorized into five groups, indicating that the PM_2.5 particles came from at least five different sources. Although elemental concentrations obtained by averaging over single particles formed in different processes will lose detailed information, we were able to derive comprehensive elemental compositions of individual PM_2.5 particles using our novel technique. The individual particle analysis technique for PM_2.5 will provide important information to identify pollution sources and particle formation mechanisms.

As part of a biomonitoring study of atmospheric particles for the development of a biological and environmental monitoring system in the beech (Fagus crenata Blume) forest ecosystem, we carried out elemental content and two-dimensional analysis of beech leaves by conventional PIXE and micro-PIXE. The beech leaves were collected from natural beech forests at eight locations in Japan. For conventional PIXE analysis of beech leaf samples, 27 elements were determined in total. Mg, P, S, K, Ca, Mn, Fe, Cu and Zn were found to be the important nutrient elements for plants at all sampling sites. According to radar chart analysis results for element (Mg, P, S, K, Ca, Mn, Fe, Cu and Zn) concentrations at each sampling site, K and P, Fe and Ca, and Zn and Cu showed relatively similar patterns. However, elements with a pattern similar to that of Mg, S, and Mn were not found. These elemental concentrations were largely different at beech leaf sampling sites. For micro-PIXE analysis of beech leaf samples from seven sampling sites (Soebetsu beech forest was excluded), scanning transmission ion microscopy (STIM) images and maps of Mg, Si, P, S, K, Ca, Mn and Fe were similar. In samples from Soebetsu beech forest, portions missing from the element distribution were observed. In particular, maps of Mg, Si, P, S, K and Ca were conspicuous. These analysis results may be important information for understanding the mechanism of plant metabolism.

We used micro-PIXE to investigate the distribution of Cs and Rb in rice grains. We succeeded, for the first time, in measuring the elemental distributions in entire rice grains (with dimensions of 6.25 mm $\times$ 6.25 mm) at micrometer spatial resolution. We found that Cs and Rb accumulated in the bran and germ of the rice. The distributions of P, K, Rb and Cs were similar within the rice grain. The concentrations of Cs and Rb in the rice were proportional to those in the soil, as well as to the exposure time. The uptake of Rb was significantly larger than that of Cs. Furthermore, the behavior of Rb was similar to that of Cs in the micrometer-scale regions in plants. It follows that the distribution of Rb can be used to investigate the behavior of radioactive Cs in plants.

Ion microbeam technology and its applications at the TIARA facility of JAEA Takasaki were summarized. In 1990, R&D of microbeam technology for TIARA was initiated in order to use an ion beam for analysis, radiation effect studies, or fabrication by the micro or nanometer scale. Three different types of ion microbeam systems with high-spatial resolutions were constructed and techniques of micro-PIXE, single ion hit and particle beam writing (PBW) were developed and applied widely in science and technology. Superior performance of these microbeams, on the other hand, was based on the highest quality of beams from the accelerators, the cyclotron in particular, which were also an important part of the R&D at TIARA.

A new micro-particle induced X-ray emission-computed tomography (PIXE-CT) system was developed at Takasaki Ion Accelerators for Advanced Radiation Application in Japan Atomic Energy Agency. In this system, scanning transmission ion microscopy-CT was performed as well as PIXE-CT for three-dimensional (3D) measurement of major elements' distributions, which are required for corrections of X-ray yields due to energy losses of projectiles and absorption of X-rays. Moreover, maximum likelihood expectation maximization algorithm has been introduced to image reconstruction because higher spatial resolution can be obtained even with less X-ray yields. Consequently, 3D distribution of trace elements in a minute biological cell less than 100 μm has been successfully obtained.

A micro-PIXE analysis system based on the ion beam analysis system by Oxford Microbeams Ltd. has been developed at the NIRS-electrostatic accelerator facility. The introduction of the CdTe X-ray detector dramatically improved the detection efficiencies for heavy elements that are important in the life sciences and environmental science. This system has been used for various projects and has provided several meaningful results, thus establishing the micro-PIXE system as an effective tool for the determination of elemental distribution with a high spatial resolution. In this paper, outline of the features of the micro-PIXE system at NIRS along with its recent application in research are introduced.

The spent PUREX solvent containing U and Pu is generated from the reprocessing process of spent nuclear fuel. The nuclear material removal is important for the safe storage or disposal of the spent solvent. Our previous study revealed that the adsorbent with the iminodiacetic acid (IDA) functional group is one of the most promising materials for designing the nuclear material recovery process. Accordingly, an IDA-type adsorbent was synthesized by using graft polymerization technology or a chemical reaction to improve the adsorption rate and capacity. The synthesized IDA-type adsorbent was characterized by micro particle-induced X-ray emission (PIXE) and extended X-ray absorption fine structure (EXAFS) analyses. The micro-PIXE analysis revealed that Zr was adsorbed on the whole synthesized adsorbents and quantified the microamount of adsorbed Zr. Moreover, EXAFS suggested that Zr in the aqueous solution and solvent can be trapped by the IDA group with different mechanisms.

To achieve the elemental characterization of particles emitted from the aircraft, we performed elemental analysis using micro-PIXE for those emitted from carbon disc brakes and tires in addition to the turbine blade particles and engine reverser particles of the exhaust produced by jet engines, and identified the characteristics of individual particles from the elemental maps. As for the elemental characteristics of aircraft source particles, the turbine blade particles contained 16 elements (Na, Mg, Al, Si, S, K, Ca, Se, Ti, Cr, Mn, Fe, Co, Ni, Cu and W), and were considered to be those of the same origin. In the case of the engine reverser particles, in addition to turbine blade particles and turbine blade wear particles (nickel alloy), atmospheric particles were found. As one hypothesis, particles containing Ti–V, Mn–W and Cu–Zn may have got altered or aggregated in the process of particles moving from the turbine blade to the engine reverser. Clumps of particles were exhibited only in the elemental maps of tire particles. These clumps of particles were shaped like they had been scraped away, and were believed to have been caused by friction between the tire and the runway. These results aid in determining the component features of particles emitted from an aircraft.