International Journal of PIXE

The low energy detection efficiency of a Si(Li) detector is measured in this work. The continuous bremsstrahlung spectrum produced by bombarding a thick C target with an electron beam is used as the standard radiation source. The bremsstrahlung spectrum for a thick C target is calculated from tabulated data assuming the thick target to consist of an array of thin layers applying the respective attenuation correction for photons emitted in each thin layer. The bremsstrahlung spectra for three incident electron energies (10, 12 and 15 keV) are measured and compared with the calculated ones. The relative efficiency is obtained and compared with a calculated efficiency based on the detector specifications. The efficiency measured for those three incident electron energies on the thick target are consistent with each other. The region limited by 2 keV < k < 6 keV, where k is the X-ray energy, exhibits a significant discrepancy between measurements and calculated efficiencies. A possible explanation of the observed discrepancy is that the real thickness of the Si dead layer is thinner than the one reported by the manufacturer. The obtained efficiency values are valid within the range 0.8 keV < k < 12.5 keV.

Micro-PIXE is capable of providing spatial distributions of elements in the micro-meter scale and its application to biology is useful to elucidate the cellular metabolism. Since, in this method, a sample target is usually irradiated with proton or α-particle beams in vacuum, beam heating results in evaporation of volatile elements and shrinking of the sample. In order to avoid these side effects, we previously developed a technique of in-air micro-PIXE analysis for samples of cultured cells. In addition to these, analysis of exposed tissue samples from living subjects is highly desirable in biological and medical research. Here, we describe a technique of in-air micro-PIXE analysis of such tissue samples. The target samples of exposed tissue slices from a Donryu rat, in which a tumor had been transplanted, were analyzed with proton micro-beams of 2.6 MeV. We report that the shape of cells and the distribution of volatile elements in the tissue sample remain uncharged when using a target preparation based on a freeze-drying method.

Non-radioactive liquid waste generated in the Kaya Memorial Takizawa Laboratory was analyzed using the PIXE system established at the Nishina Memorial Cyclotron Center. Samples of the liquid waste were collected at several stages of the non-radioactive liquid waste purifying process. A simple sample preparation method for liquid sample was adopted. Liquid sample was dropped and dried directly on the backing film after adding the internal standard element, which produced appropriate targets to be analyzed by PIXE. Sodium, silicon, sulfur, chlorine, potassium, calcium, iron and so on in the liquid sample were detected. The PIXE method used in this study showed outstanding properties for analyzing the liquid sample.

The paper presents the verification of home made Position Sensitive Spectrometer (PSS) while using synchrotron radiation light (SRL) as an excitation source. When Cr in the substance of light base was analyzed by the PSS, the lowest detection limit of a few ppm was achieved. Also linear proportionality between the count rate of the PSS and Cr concentration was obtained. This verities the feasibility of trace element analysis with high-energy resolution when using the PSS. At measurement of Cr Kβ₅ band in metallic Cr and its compounds, it was discerned that the intensity of Cr Kβ₅ becomes more intense with increasing oxidation number of Cr compounds. Such a change shows that high-energy resolution analysis using the PSS can make a useful method for the study of chemical states.

By building up a cryo-preparation laboratory a method was developed which allows us to prepare cryo sections of fully differentiated plant-root material, according to the requirements of the proton microprobe. Since cryo-preparation is the only possible method delivering reliable elemental distributions, this step was a fundamental for all our further investigations in plant root physiology. As an example, PIXE-investigations of a root section of a heavy metal hyper-accumulating plant Brassica juncea L. will be presented.

Common bullies, Gobiomorphus cotidianus, are a widespread small New Zealand freshwater fish, with a life-cycle that may include an optional juvenile marine phase. We used the strontium variation in fish otoliths in an attempt to track the life history of the individual fish since the interlayer variation reflect the exposure of fish to background environmental levels of Sr at the time of deposition. One possible mechanism by which Sr can be enriched in otoliths is by seawater, which usually has a higher Sr/Ca ratio than fresh water. Locally resolved elemental measurements with a proton microprobe enable therefore the detection of variation in Sr that may reflect single or multiple migrations of freshwater fish into seawater. The most striking feature of this study is the observation of high Sr/Ca ratios in the cores of all otoliths, including those from fish caught 50 km inland. This suggests different environments in the life cycle of common bullies in the lower reaches of the Clutha river. A marine juvenile phase may be a common feature. Preliminary area scans were used to select suitable transects for detailed line scans which gave greatly improved statistics.

It has been reported that edible mushrooms are able to enrich the concentrations of several heavy metals. The Cd has especially drawn attention due to its high toxicity. By using PIXE analysis for the determination of the heavy metals it is possible to obtain a screening of the content of a wide number of elements. By analysing different species it is shown that one or a few elements may be characteristic for a single species. It is especially remarkable that several species of the family Agaricaceae are enriching Ag to a very high degree (up to 200 ppm).

In order to address global environmental issues, a standard-free method developed by ourselves has been successfully applied to various kinds of bio-samples. Especially, a method for untreated hairs has been applied in many polluted areas to study human exposure to toxic elements. In addition to hair, nail is expected to give us valuable information about human exposure to toxic elements. However, the analysis requires relatively large amounts of samples and laborious sample preparation techniques which necessitate internal standards. In this work, we have developed a quantitative method for untreated human-nail analysis based on the standard-free method. It requires neither large amounts of nails nor complicated target preparation procedure. Furthermore, it is perfectly free from any ambiguity in target preparation such as volatilization of certain elements and contamination of the sample during chemical ashing. The optimum conditions of irradiating nail samples are established, and accuracy and reproducibility of the present method are confirmed. It is found that ultrasonic washing in distilled water is effective for many nail samples preventing the loss of elements from the sample. It is also found that elemental concentration in nails strongly depends on their sampling positions.

Particle Induced X-ray Emission (PIXE) was used to analyse the elemental concentration of gallstones collected from different parts of south India. Cholesterol gallstones are predominant in north India, whereas pigment gallstones are predominant in south India. The black pigment gallstones are common in hemolytic anemia or in presence of infected bile. PIXE has revealed the elemental profile in each sample. The experimental subjects of the different groups displayed significant variation in their levels of certain trace elements such as copper, zinc, and iron. The concentration of copper was found to be predominant in pigment gallstones investigated in the present study.

In 30 healthy persons (control), 17 renal cell carcinoma (RCC) patients, 30 hemodialysis patients (HD) and 15 healthy persons in the Takko town (Aomori prefecture), the selenium concentration in serum was determined by PIXE. The mean serum selenium concentration in healthy controls was 1.4 ± 0.6 μmol/l, in RCC patients 1.1 ± 0.4 μmol/l, in HD patients 1.3 ± 0.9 μmol/l and in healthy persons in the Takko town 1.7 ± 0.7 μmol/l. There was a significant statistical difference between RCC patients and healthy persons in the Takko town (p < 0.05). Takko town is famous for the production of garlic. Epidemiological studies have established an inverse relationship between garlic consumption and incidence of gastric, colon, and laryngeal cancers. Garlic is a rich source of selenium in the food. Contents of selenium in normal and carcinoma fractions in kidneys of RCC patients were determined by PIXE. The results indicate that RCC patients caused significant decrease of selenium contents in the carcinoma fraction (p < 0.05).

Geosiphon pyriforme is a unique symbiosis between a fungus, belonging to the arbuscular mycorrhizal (AM) fungi, and a cyanobacteria (blue-green algae). Since more than 80 % of the land plant species form an AM, the importance of this symbiosis becomes evident. In our research on heavy metal uptake and resistance of plants, Geosiphon is used as a model system for the AM symbiosis. Whilst we have studied heavy metal uptake of Geosiphon pyriforme from a macroscopic point of view we will now present first and preliminary results of element distributions in heavy metal stressed and non-stressed cryo-sections of Geoslphon pyriforme.

We made a comparative study of the trace elements in the oral mucosa of 22 patients with oral lichen planus (OLP) and of 100 healthy persons by the PIXE method. Samples were excised from the oral mucosa of the OLP patients (OLP group) and from the buccal mucosa of healthy persons (control group). The results were as follows: Seventeen trace elements and 11 contaminating elements were detected in those oral mucosae. Al, Ti and Pb, which are contaminating elements, were detected in more than 65% of samples from both groups. The mean values of Se and Rb were significantly lower in the OLP group than in the control group. The mean values of the other elements did not differ significantly between the groups. As for the females over 30 years old, the OLP group showed significantly higher values of Zn and Sr than the control group. Their mean values of the other essential and contaminating elements did not differ significantly between the groups, although there was a trend toward higher values in the OLP group. We found by the PIXE method that Zn, Fe and Pd, which are d-transitional elements considered to cause allergic reaction, showed higher values in the oral mucosae of the OLP patients than in those of the healthy persons.

Lichen samples were collected and observations about lichen communities were recorded at sites in the intermountain western United States. Specifically the states of Idaho, Montana, Wyoming, Nevada, Utah, Colorado, Arizona, and New Mexico were included in this study. The minor and trace-element concentrations in many of the lichens collected were determined by proton induced X-ray emission (PIXE). These data are part of a base line assessment of current air pollution conditions in this region. These data also provide an opportunity to study some aspects of lichen physiology. Using the data from 508 foliose and fruticose lichens, frequency distributions for concentrations of phosphorus and calcium are considered. Phosphorus has a closely-spaced, bimodal distribution: one mode for foliose lichens and one mode for fruticose lichens. This suggests that all lichen genera in this study have similar requirements and absorption mechanisms for phosphorus. Calcium has a complex frequency distribution and concentrations that range from 450 mg/kg to 14 % dry weight. Contributions to this complex distribution pattern can be understood if the data are resolved into growth form, genera within each growth form, and in some cases species within a given genus. This complex dependence on calcium is strong evidence that lichens develop specific calcium-related adaptations in order to accommodate various habitat conditions.

Artisanal/small-scale gold mining is one of the important livelhood for deprived people in many countries. The activity is expected to support people's life and activate local economy. However amalgamation method is common to recover gold in this type of mining, and due to this practice, mercury is being released into the natural environment. During the ore treatment process, miners uptake mercury not only by inhalation of the vapor but also by absorption of liquid mercury through the skin. In order to cope with health problems and environmental damages arising from the use of mercury, there should be coordination between national/local government, aid agencies and scientific institutes. In addition, the environmental education and risk communication are keys to mitigate the environmental damage by the miners. For such purpose, quick and precise trace element analysis as a base of discussion on occupational health risk is indispensable and our trial proved that PIXE is one of the most flexible and versatile system. In this paper examples of trial through a Japan-Philippines partnership will be presented.

Elemental concentrations of Sr, Fe, Zn and Cr have been measured by in-air and microbeam PIXE to track the changes during the stalagmite growth. The objective was to find the optimal parameters for the measurements of available isotope-dated stalagmite cuts from Slovenian Karst. Significant concentration fluctuations of Fe, Sr and Cr at the scale of several millimetres have been observed by in-air PIXE. Fluctuations of trace elements observed by microbeam PIXE are contributed to the sub annual periods of growth. As demonstrated, a two-dimensional Ca, Sr, Fe and secondary electron mapping is required to avoid regions with mineral inclusions and surface irregularities during line scans over the speleothems. Optimal measuring parameters for microbeam PIXE mapping of large stalagmite cuts already mapped by isotope dating are given. These measurements would account for sub-annual growth fluctuations.

PIXE measurements on filtered water samples were conducted to investigate the possibility of using nuclear based analytical techniques to measure elemental concentrations of heavy metals in suspended sediments in the Waiwhetu Stream (Lower Hutt, New Zealand). It was found that most of the elements detected have a concentration of around 100 ppm by weight with 10 percent variation. Heavy metals like Cu, Zn, Pb and Cd were also present at higher than normal concentrations in the stream. Previous studies of the sediments collected from the Waiwhetu stream had showed that high levels of heavy metals were present at locations close to industrial sites, Nowadays, industries are no longer permitted to dump their waste into the stream. However, high-levels of heavy metals were found to be still present in the water samples indicating that these elements are slowly washed out of the sediments into the surface waters. The present results of Waiwhetu stream water samples revealed that heavy metals are distributed throughout the stream indicating that industrial wastes from industry discharges still linger after 30-40 years.

In cooperation with the Shanghai Environmental Specimen Bank (SESB) research project and in support of the Shanghai government's comprehensive plan to harness the Suzhou River, we collected water and sediment samples in the every spring season since 1998. The elemental analysis of sediment and water samples was performed by the PIXE technique using the 3 × 2 MeV NEC Tandem accelerator at the Taipei Institute of Physics. The characterization of á and â radioactive levels for water and sediment samples was performed using BH1216, low-background, radioactivity instrument at the Shanghai Institute of Nuclear Research. PIXE results showed that the content of Cl, K, Ca, Cr, Mn, Fe, Zn and Pb in river water gradually decreased with the rising tide. At high tide, their concentrations were minimum, and then once again increased toward the ebb tide. The analysis also demonstrated that the radioactivity of water samples had been gradually decreasing year by year. It was found that the decreasing rate of á radioactivity was a little quicker than that of â radioactivity. Further aspects of environmental data evaluation and assessment are also discussed in detail.

In this study, we carried out PIXE analysis of raw and treated water at five water treatment plants as well as of tap water from several houses located in each supply route. We used a simple fast procedure for preparing thin uniform targets of inorganic components in both soluble and insoluble fractions of aqueous samples in combination with preconcentration of trace heavy metals; that is, Nuclepore filtration targets for coarse particles, preconcentration targets for heavy metal ions and deposit targets for fine particles and soluble major constituents. The target preparation and the PIXE measurement are not time-consuming, and a broad range of concentrations (several tenths of ppb to a few tens of ppm) of 19 elements from Na to Pb is determined simultaneously with a precision sufficient to reveal the elemental distribution in the soluble and insoluble fractions. Tap water quality was examined as a function of elemental distribution in untreated water at the plants. We confirmed the increase of insoluble components of some heavy metals in untreated water taken from river due to heavy rainfall and the elution of Cu, Zn and Pb in drinking water by corrosion of the piping in some part of the water distribution systems.

An ion-exchange cellulose phosphate filter was used to prepare in-line PIXE targets for long-term monitoring of heavy metal concentrations in river and tap water. River water samples were taken every 30 minutes during 7 hours, and tap water samples every 5 hours during 150 hours. A PIXE target was prepared passing 300 ml of water sample and 2 ml of 20 ppm Y standard solution through a single sheet of the filter paper. Heavy metals (Mn, Fe, Cu, Zn, Pb and Hg) were detected by PIXE analysis with lower detection limits of 0.5-1.0 ppb. Analysis results show that the filter paper can trace concentration changes of heavy metals in a wide range.

It is well known that green roof systems are being used to improve the environment by reducing the summer temperatures inside the houses and to capture atmospheric contaminants. The Universidad Autónoma de Chapingo had begun a project to test the latter possibility in Mexico City, were some roofs were covered with the plant Sedum praealtum L. By PIXE analysis, metal concentrations were determined in ashes of the leaves and stems. The concentrations were compared with those of the substrata and plantations grown in a greenhouse, which were used as a reference. Preliminary results are presented.

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.

Chinampas are island plots (500-1000 m²) constructed of soil scooped from the bottom of the lake and surrounded by canals. Over 40 agricultural species, including vegetables, cereals, and flowers, are produced on chinampas and consumed by approximately 100,000 people. This agro-ecosystem, once one of the most diverse and productive, at present is at risk of disappearing, mainly as a consequence of the severe pollution of the irrigation water. To evaluate the relationship between the accumulation of metals and physical soil properties, total trace metals Fe, Cu, Mn and Zn and total heavy metals Pb, Ni, and Cr in soils were determined by Particle Induced X-Ray Emission (PIXE). This method provides a very suitable technique for treating a large number of samples because sample preparation is simple and determination of a large number of elements is simultaneous. Three sites were chosen because of their long history of pollution: Xochimilco, San Luis Tlaxialtemalco and Mixquic in Mexico City. Soil properties were determined by conventional analytical methods. Soils were found to be high in organic matter content, high in sodicity and salinity, and with an alkaline pH. The metals present in the samples are in the following order of abundance: Fe>Mn>Cr>Zn>Cu>Pb.

Several samples of pottery sherds owned by the Islamic Arts section of the National museum of Iran excavated in Ray, Neishabur and Kahn – the area around northeast and the central part of Iran – were analyzed in order to establish their chemical compositions. In Van de Graaff Laboratory at the AEOI, qualitative analyses of the sherds were performed using a 2 MeV proton beam. The fragments which dated back to the period between the 9^th and the 13^th centuries, were analyzed using the PIXE method. The results of the concentrations of the component elements such as Ti, Mn, Fe, Co, Ni, Cu, Zn, Ba and Pb are presented and discussed. The results confirm the effect of the iron content of clay, it's firing conditions such as firing temperature, oxidation and reduction on the color of clay. In addition the dependence of glaze color with the various elemental concentration is established.

Luster is a special type of decoration, which gives ceramics a particular iridescent gold translucency and was applied to the medieval surface of glazed pottery. In this work the PIXE technique has been applied to luster pottery dated back from the 10^th to the 13^th centuries, excavated in Neishabur, Ray and Kashan, located in the northeast and in the central part of Iran. The principal elements of the glaze were detected, as well as the elements which characterize the luster, such as Cu and Ag. The elemental concentrations of Ti, Mn, Fe, Co, Cu, Zn, Ag, Sn and Pb were also obtained from the PIXE analysis. This study clearly demonstrates that in addition to firing conditions and the presence of impurities in glaze, the ratio of Cu₂O/Ag₂O determines the color effect of luster.