T. Satoh

Application of micro-PIXE technique to uptake study of cesium by Saccharomyces cerevisiae

Abstract We examined the accumulation and distribution of Cs, and the presence of other elements in yeast ( Saccharomyces cerevisiae ) cells by the micro-PIXE (particle induced X-ray emission) system developed at the TIARA facility, JAERI, and by energy dispersive spectroscopy (EDS) coupled to a scanning electron microscope. The effects of Cs on yeast growth were determined by measuring the optical density at 600 nm. Addition of 1 mM Cs did not have any effect on the growth of the yeast. Micro-PIXE analysis of cells grown in the presence of Cs showed that Cs was uniformly distributed in the cells. Using PIXE, Cs, P, K and Fe can be detected, whereas only P and S can be determined by the EDS. Cells exposed to Cs showed an increase in Cs peak intensity, and decrease in P, K and Fe with time. These results suggest that micro-PIXE is a useful technique to detect low concentration of toxic elements in microorganisms as well as to monitor their changes as function of growth.

Micro-pixe study on sorption behaviors of cobalt by lichen biomass

Abstract Sorption behavior of Cobalt (Co) by lichen biomass has been studied in the foliose lichen Permotrema tinctorum in solution between pH 3 and 5. Disc of P. tinctorum, weighing ≈9 mg was incubated in 25 ml 0.1 M NaCl solutions containing 1 mM Co for up to 96 h. Concentrations of Co in the solutions were measured at 24, 48, 72 and 96 h by ICP-AES. Spatial distribution of Co, K, P and Fe in the cross-section of P. tinctorum was examined by in-air μ-PIXE (particle induced X-ray emission) technique developed in the TIARA facility of JAERI. Sorption of Co by P. tinctorum reached equilibrium within 24 h. Co uptake was averaged to be 27 dry wt.%, and was independent of solution pHs between 3 and 5. Two-dimensional distribution of Co indicates that the sorbed Co was localized, and the density of Co in the lichen was ordered lower surfacexa0>xa0upper surface, medullary layerxa0>xa0algal layer. Highest density in the two-dimensional distribution of Co is obtained in the lower surface suggesting that Co was sorbed by melanin-like pigment contained in the lower surface. Two-dimensional distribution of Co did not correspond to Fe indicating that Co was not adsorbed on the Fe-containing minerals trapped on P. tinctorum. It is concluded that μ-PIXE analysis is a useful technique to detect the distribution of low concentration of elements in lichen biomass.

Uptake of cadmium by synthetic mica and apatite: Observation by micro-PIXE

Abstract This study investigated the uptake of Cd by a mixture containing equal mass of two powerful sorbents for Cd, a synthetic mica named ‘Na-4-mica’ and an apatite, by micro-particle-induced X-ray emission (micro-PIXE) analysis. Divalent Cd ions were found to be selectively taken up by the apatite from the mixture even though it has one order of magnitude lower distribution coefficient for Cd2+ than Na-4-mica. This was mainly attributed to the fact that the kinetics of uptake by the apatite were more rapid than those by Na-4-mica. Regarding the uptake of Cd colloids containing hydroxides and carbonates, no clear selectivity for solid phases was observed and Cd colloids appeared to be preferentially taken up by smaller particles of solid phases.

PIXE Analysis of Trace Heavy-Metals in River Waters Using an Ion-Exchange Cellulose Filter Paper

A simple but precise method for the PIXE analysis of trace heavy-metals in aqueous samples was developed, in which the PIXE targets were prepared by pre-concentrating heavy metals on a cellulose phosphate ion-exchange filter paper and no additional chemical treatment was required. Heavy metals in trace concentrations were quantitatively retained up to 16.7 μ-equivalent on a sheet of filter paper due to the excellent selectivity for heavy metals and ion-exchange kinetics of phosphate groups in cellulose matrix. Heavy metals of less than 1 μg on one filter paper are precisely and rapidly determined by PIXE analysis using 3-MeV proton beams. The present method is compared with the method preparing a PIXE target for each dissolved species of an element contained in aqueous samples. It will be resulted that the newly developed method enables an on-line PIXE analysis for river waters.

MULTI-SITE AEROSOL MONITORING USING MINI STEP SAMPLER

We developed mini step samplers with low manufacturing and running costs for application in multi-site air-pollution monitoring. The miniaturization of the sampler was achieved by reducing the suction nozzle size. We tested the samplers with suction nozzle diameters of 2 and 4 mm through simultaneous exposure in the same site. Elemental concentrations of aerosol collected by these samplers were consistent within ±20% during comparison and the sample uniformity did not differ significantly. Sampling with small suction nozzle did not adversely affect aerosol collection. Aerosol samples were collected simultaneously at two sites in our laboratory and in the hall outside for 3 days and analyzed subsequently by PIXE. The time variation of elemental concentrations was high during daytime and low at night time and also during the weekend. Elemental concentrations in the hall were always higher than those in the laboratory. In our laboratory, we change shoes at the entrance and therefore, elemental concentrations inside the lab are lower than in the hall. In a second field experiment, we carried out simultaneous multi-site aerosol sampling during two periods in correlation with meteorological data (wind direction and velocity). It was observed that elemental concentrations of some soil origin elements changed periodically. On the other hand, the concentration of Cu and Zn showed irregular concentration spikes whose pattern showed a variation with the sites. Analysis using the data of wind directions showed that Cu had been transported to the sites from northeasterly direction and that the concentration of Zn was influenced by two big factories nearby. In conclusion, it has been demonstrated that the multi-site sampling system combined with meteorological data is well suited to identify sources of pollution.

IN-AIR MICRO-PIXE ANALYSIS OF TISSUE SAMPLES

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.

PIXE ANALYSIS OF TRACE HEAVY METALS IN RIVER AND TAP WATER USING AN ION-EXCHANGE CELLULOSE PHOSPHATE FILTER

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.

BEAM DAMAGE OF CELLULAR SAMPLES IN IN-AIR MICRO PIXE ANALYSIS

The change of shape and elemental concentration of cellular samples in In-Air micro PIXE analysis was investigated. Cultured bovine aortic endothelial cells were analyzed in the atmosphere by using 2.6 MeV proton micro-beams. The shape of cross-sections of cells was not so much distorted by beam irradiation and the concentrations of trace elements did not change too, except for S. The concentration of S changed with strongly depending on the temperature rise due to beam irradiation.

PIXE ELEMENTAL ANALYSIS OF DRINKING WATER SUPPLIES

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.

3D imaging of elemental distributions using multi-angle RBS 2D-data

Abstract We developed a novel technique to obtain 3D-imaging of elemental distribution based on multi-angle RBS measurement and micro-beam scanning. Since cross-sections of RBS are too small to obtain 3D-imaging, it is necessary to measure scattered particles with large solid angle detectors. Hence, the RBS profiles from each scattering angle are superposed and a true depth profile cannot be obtained. Recently, a large solid angle X-ray detector array consisting of 45 detector elements was installed at the TIARA facility of Japan Energy Research Institute. Each detector element measures X-rays as well as scattered particles. For this utilization, we introduced a technique to superpose RBS profiles and applied it to the surface analysis of an ant’s head.