Individual particle analysis using micro-PIXE and proton backscattering was performed for selected aerosol samples collected over Siberia. Point analyses were complemented by x-ray mapping for complex particles. Hierarchical cluster analysis of 124 particles identified in general the same particle groups, as found by automated electron microprobe analyses of approximately 25000 particles from the same locations. However, owing to the superior sensitivity of micro-PIXE, a number of heavy metals were identified, suggesting an anthropogenic origin of particles. These metals remained undetected by EPXMA owing to its inferior sensitivity. Elemental mapping of single aerosol particles yielded important information on the chemical heterogeneities. Copyright (C) 2001 John Wiley & Sons, Ltd.

The distribution of nickel and other elements was investigated in freeze-dried young leaves of Berkheya coddii Roessler (Asteraceae), one of the five nickel hyperaccumulating plants from South Africa. Two-dimensional quantitative maps were generated to determine the distribution of Ni, as well as macro- and micronutrients, using the scanning nuclear microprobe of the National Accelerator Centre. The highest Ni enrichment was found in leaf margins, leaf mesophyll and midrib epidermis of very young apical leaves.

An original method has been developed to measure the lateral straggling of sub-micron proton and alpha beams after passing through polymer foils of different thickness. For this purpose, the microbeam line at CENBG has been used in scanning transmission ion microscopy (STIM) configuration to deliver the ions in normal incidence on foils. The lateral spreading of the beam was measured using a collimated charged particle detector centred on the beam axis and placed 6.3 mm behind the foil. When the beam was horizontally scanned in front of the collimator, its lateral distribution was measured step by step detecting particles passing trough the small aperture. Regular gaussian shapes were obtained and data were compared to the result of simulations carried out using the SRIM Monte-Carlo code for 2.5 MeV protons and alphas in Mylar and Formvar thin films.

Senecio sp. aff. S. anomalochrous Hilliard (Balkwill 6869 J) Asteraceae, one of five Ni hyperaccumulators in South Africa, was collected from serpentine outcrops near Kaapsehoop Chrysotile Mine (Mpumalanga). Bulk analysis of freeze-dried materials was done by ICP-AES. Studies of two-dimensional elemental distributions were performed using the NAC nuclear microprobe. A gradient of concentrations, increasing from root to leaf, was observed. The highest Ni enrichment was found in the leaf; this is typical of hyperaccumulators. Elemental maps of Ni from leaf cross-sections showed that Ni was present everywhere in the leaf tissue, but in different concentrations. The association of Ni with certain tissues, such as the epidermis, was clearly visible, similar to the trend of Ni concentration in other hyperaccumulators from South Africa, Senecio coronatus and Berkheya zeyheri subsp. rehmanii var. rogersiana. The relationships between Ni and other elements were also investigated.

A single event facility is currently under development at CENBG for applications in radiation biology. The aim is to induce the response of living cells by hitting selected individual specimens or specific sub-cellular compartments with an exact number of light ions. In order to avoid the construction of a complete beam line, it was decided to adapt the existing microprobe system. The line has been equipped with a removable final irradiation stage constituting a versatile system working on demand either in external beam mode or classical analysis under vacuum. The beam blanking is ensured by particle detectors which have been specifically designed to control MeV proton or alpha beams in a single event mode. This paper presents the overall experimental setup and first in-air experimental tests.

The use of particle-induced x-ray emission (PIXE) in conjunction with a scanning nuclear microprobe (SNM) offers one of the few microanalytical techniques capable of studies of elemental concentrations at the ppm level, with a spatial resolution of the order of 1 mum. Beam scanning capabilities and advanced data treatment make it a technique of choice for quantitative two-dimensional studies of elemental distribution. Although the ultimate aim is to obtain true quantitative elemental maps, free of concentration or thickness artifacts, some compromises are necessary owing to experimental and computational restrictions. Some approaches currently used are discussed with emphasis on true elemental imaging using the dynamic analysis method. Examples of applications in geology and biology are shown to illustrate its benefits and limitations. Copyright (C) 2001 John Wiley & Sons, Ltd.

The nuclear microprobe (NMP) unit of the National Accelerator Centre (NAC) has initiated a focused research programme on studies of biological material, ranging from applications in medicine to agriculture and botany. During this period a state-of-the-art cryo-preparation laboratory was also developed. This research programme has resulted in a wide range of projects, and has shown how well suited the NMP is for studies of biological material in general. This paper reports on some of the problems and demands in this field, as well as some of the results obtained using particle induced X-ray spectroscopy (PIXE) and Rutherford backscattering (RBS). True elemental imaging is routinely performed using the dynamic analysis (DA) method, which forms part of the GeoPIXE suite of programmes. A collaborative project, together with the CENBG group of Bordeaux–Gradignan in France, on the development of a facility with the aim of studying effects of single-events of radiation in living cells was recently established and is discussed.

Elemental levels and distributions in various organs (leaves, upright stems, rhizomes and roots) of the seagrass Thalassodendron ciliatum were determined using the NAC nuclear microprobe. Elemental distributions were obtained using the true elemental imaging system Dynamic Analysis (DA). Cl was the most abundant element present in the organs, occurring in all tissues, but present in relatively low concentrations in epidermal cells of leaves and roots. Na, K, S and Mg were also abundant and occurred in all organ tissues. Ca concentration was highest in the leaves, especially in the epidermis. Low concentrations of P were found and its tissue distribution was limited. Although Fe, Cu, Zn, Mn, Br, Ti and Si were present in relatively small amounts, enrichment of the epidermis with Fe, Ti and Si in all organs, was observed. Fe concentration was the highest in rhizomes while Si concentration was highest in upright stems. The significance of these elemental distribution patterns and the value of the nuclear microprobe in elemental analysis of seagrasses are discussed.

The nuclear microprobe (NMP) is an established analytical instrument for the determination of minor and trace elements, It allows measurements with a spatial resolution of the order of 1 mu m and minimum detection limits down to few ppm by weight, with excellent scanning capabilities. The nuclear microprobe of the National Accelerator Centre, South Africa, is being used in a wide number of applications in the biosciences. The complementarity of proton-induced x-ray emission and backscattering spectrometry in a wide range of biological applications is shown. The advantages and restrictions of true elemental imaging are also discussed. Copyright (C) 1999 John Wiley & Sons, Ltd.

Glass bottles, used for sparkling wine, are treated with freon during manufacturing to harden the inside surface. Although this type of treatment normally improves the properties of the glass, in this case the occurrence of “egg” formations (egg-shaped rough areas) on distinct areas of bottles, as well as yeast sticking to the insides of bottles at specific areas pointed to the possibility of different areas showing different properties in the same bottle. The question was whether the correct gas was used for the treatment, and secondly, whether the process was controlled well enough to obtain the correct properties for the inside of the glass. We present results of an optical microscopy and nuclear microprobe (NMP) investigation.

The distributions of sodium and chlorine in leaf cross sections of the seagrasses Zostera capensis and Thalassodendron ciliatum were studied using the true elemental imaging system (Dynamic Analysis) of the NAC nuclear microprobe. Analyses were performed using protons of 0.6 and 1.5 MeV and experimental conditions were compared in detail, Using protons of 0.6 MeV is recommended for mapping of Na, Mg and Al. (C) 1999 Elsevier Science B.V. All rights reserved.

The Ni hyperaccumulator, plant species Senecio coronatus (Thunb.) Harv., Asteraceae is an example of plant adaptation mechanisms to different ecological conditions. This widespread species can inter alia be found on serpentine outcrops and the genotypes growing in serpentine soils show different ways of adaptation. The populations from two distant localities take up and translocate Ni in concentrations which are normally phytotoxic, while plants growing on a different site, in the vicinity of another hyperaccumulating species, absorb amounts which are typical for most of the plants found on serpentine soils. The NAC nuclear microprobe was used to compare the distribution of Ni and other elements in selected organs and cells with simultaneous use of PIXE and proton BackScattering (BS). Quantitative maps of stems showed large differences in concentrations and distributions of major and trace elements. In hyperaccumulating genotypes Ni is present everywhere within stem tissues, but the highest concentrations were found in the epidermis, cortex and phloem. In non-accumulating plants Ni was concentrated in the phloem. In the leaf epidermis Ni was concentrated in the cell walls for both accumulating and non-accumulating plants. These results suggest that biochemical diversity is more than morphological, because investigated genotypes belong to the same taxon.

A Brachiaria breeding project is being conducted at CIAT, Colombia to combine acid soil adaptation of B. decumbens with other favourable traits of Brachiaria species that are less adapted to acid soils. Micro-PIXE was applied to investigate nutrient uptake and distribution in root tips of different species grown in hydroponic culture under control and simulated acid soil stress conditions. Different sample measurement approaches were evaluated, including: (1) linear scans with single point measurements along the root axis; (2) mapping of whole root tips; and (3) mapping of root cross sections. Different tissue types could be distinguished on the base of differences in nutrient concentrations and/or Al stress. Al, if supplied under nutrient stress conditions, increased P accumulation in the central vascular tissue of the meristematic and elongation zone of B. decumbens and B. brizantha. Furthermore, a negative correlation was found between Al and Cl accumulation in the root cap of B. decumbens.

In this study, patina layers on artefacts composed of different rock types were examined, with all specimens originating from arid and semi-arid environments of South Africa. Microscopic observations showed a continuous mineralogical change from the unaltered core to the rim, suggesting that the patina layer is the result of weathering and/or chemical leaching of the rock surface. Elemental mapping by micro-PIXE and SEM showed depletion in leachable elements such as Mg, K, Ca, Fe and to a lesser extent Al, Si and Mn towards the surface for all artefacts analysed. This kind of distribution suggests the possibility that a leaching and exudation process through fluid activity might be responsible for the gradual, and in some cases extensive removal of the elements towards the patina surface.

The technique of Dynamic Analysis (DA) has been applied to obtain information on the distribution of minor components and trace elements (TE) in a series of calcium oxalate (CaOx) human kidney stones by nuclear microprobe (NMP) determination. In the present study microanalysis was further expanded to include information on Na, Mg, Al, Si, P, S and Cl. Interest was also focused on determining levels of directional variability in elemental concentrations of Ca, minor components and TE throughout selected micro-regions of single stones by DA.

Single fly ash particles were analyzed by using a combination of electron microprobe and nuclear microprobe measurements. Trace elements were found to accumulate in these particles by three different mechanisms. Firstly, in some particles trace elements remain associated with unaltered mineral phases. In the second instance, some minerals containing trace elements were dissolved in larger particles, and thirdly, volatile trace elements were found to have reacted with molten fly ash particles, especially in particles which approach eutectic compositions in the FeOAl2O3SiO2 and CaOAl2O3SiO2 ternary systems.

An overview of botanical applications in the field of nuclear microscopy is presented. A wide range of applications has been studied up to now and included an array of very thin to thick samples. The relevant methods of sample preparation which are critical to many botanical applications are discussed. Quantitative mapping techniques allowing simultaneous quantitative studies of major and trace elements offer exciting possibilities in various fields of application, from science to industry and agriculture. In these studies PIXE and RBS were typically used to obtain complementary information. Recent examples are presented.

Three ordination methods and three clustering methods were compared, using the same data from proton induced X-ray emission (PIXE) analysis of two visually distinct pottery types found in the same area of the upper Karoo region in South Africa. Petrographic analysis of these two Later Stone Age ceramic traditions indicate that geologically distinct clays and temper were used for each. The PIXE data show, however, that the separation is not as perfect as appearances suggest—some “hybrid” specimens are present. To determine whether these hybrids were a spurious byproduct of our statistical manipulation, we applied correspondence analysis, principle components, multidimensional scaling, and three versions of Q-mode clustering. The same hybrids showed up in most applications. Correspondence analysis achieved the most complete separation, but the real benefit was from the combined insights afforded by all techniques. Although a weak separator, Ward’s minimum variance method of Q-mode clustering proved more useful for discriminating spatially discrete subgroups of vessels within the 2000km2study area.

Previous studies on the role of trace elements (TE) in the development of calcium oxalate (CaOx) human kidney stones by nuclear microprobe (NMP) investigated the mechanisms and role of TE in the buildup of urinary CaOx concretions. In the present work, microanalysis of the previously reported series of recurrent human kidney stones was further expanded. Interest was focused on determining levels of directional variability in elemental concentrations of Ca and TE throughout selected micro-regions of single stones by Dynamic Analysis (DA).