[show abstract][hide abstract] ABSTRACT: Stackhousia tryonii Bailey is one of the three nickel hyperaccumulators reported from Australia. It is a rare, herbaceous plant that accumulates nickel (Ni) both in leaf and stem tissues. Localisation of Ni in leaf and stem tissues of S. tryonii was studied using two micro-analytical techniques, energy dispersive X-ray spectrometry (EDXS) and micro-proton-induced X-ray emission spectrometry (micro-PIXE). Dimethylglyoxime complexation of Ni was also visualised by bright-and dark-field microscopy, but this technique was considered to create artefacts in the distribution of Ni. Energy dispersive X-ray spectrometric analysis indicated that guard cells possessed a lower Ni concentration than epidermal cells, and that epidermal cells and vascular tissue contained higher levels of Ni than mesophyll, as reported for other Ni hyperaccumulators. The highest Ni concentration was recorded (PIXE quantitative point analysis) in the epidermal cells and vascular tissue (5400 µg g −1 DW), approximately double that recorded in palisade cells (2500 µg g −1 DW). However, concentrations were variable within these tissues, explaining, in part, the similarity between average Ni concentrations of these tissues (as estimated by region selection mode). Stem tissues showed a similar distribution pattern as leaves, with relatively low Ni concentration in the pith (central) region. The majority of Ni (73–85% for leaves; 80–92% for stem) was extracted from freeze-dried sections by water extraction, suggesting that this metal is present in a highly soluble and mobile form in the leaf and stem tissues of S. tryonii.
[show abstract][hide abstract] ABSTRACT: Elevated concentrations of lead were found in Australian free ranging saltwater crocodile (Crocodylus porosus) bone and flesh. Lead shots were found as potential source of lead in these animals. ANSTO’s heavy ion nuclear microprobe was used to measure the distribution of Pb in a number of bones and osteoderms. The aim was to find out if elevated Pb concentration remains in growth rings and if the concentration is correlated with the blood levels recorded at the time. Results of our study show a very distinct distribution of accumulated Pb in bones and osteoderms as well as good correlation with the level of lead concentration in blood. To investigate influence of ion species on detection limits measurements of the same sample were performed by using 3 MeV protons, 9 MeV He ions and 20 MeV carbon ions. Peak to background ratios, detection limits and the overall ‘quality’ of obtained spectra are compared and discussed.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2003; 210:330-335. · 1.27 Impact Factor
[show abstract][hide abstract] ABSTRACT: The timing properties of a silicon-on-insulator microdosimeter for medical and space applications have been studied using an ion microprobe. These measurements were used with a pulse shape discrimination technique to render the microdosimeter insensitive to ion strikes outside the ideal sensitive volume.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 01/2003;
[show abstract][hide abstract] ABSTRACT: Nuclear milli and microprobes at the Australian Nuclear Science and Technology Organisation (ANSTO) were used to determine lead accumulation in native Australian plants and animals. Three species of eucalypt plants (Eucalyptus camaldulensis, Eucalyptus globulus and Eucalyptus lesouefii), one species of salt bush (Atriplex burbhanyana) and one species each of acacia (Acacia saligna) and estuarine crocodiles (Crocodylus porosus) were investigated. Experimentally grown plants were subjected to a nutrient solution with a pH of 5 and spiked with a 200 μmol concentration of Pb. Lead concentrations in leaves of both E. globulus and E. camaldulensis showed an almost exponential decrease from the base of the main vein to the tip. Similarly, Pb concentrations decreased from the main vein to secondary veins. Concentrations of essential elements such as K, Fe, Zn and Br in the main and secondary veins were constant within experimental uncertainty. In contrast, the concentrations of Pb in the leaf veins of E. lesouefii were much lower and showed no systematic pattern. In stem and root samples the highest concentration of Pb was found in roots and stem of E. globulus and A. burbhanyana followed by E. camaldulensis. Some Pb was found in roots of A. saligna and only very low concentration in stem of the same plant. More detailed analysis of thin cross-sectional samples of roots and stem showed that Pb is present in much higher concentration in the growth area of the plant structure (i.e. meristemic region) and in relatively low concentration within the pith region and outer cortex. The osteoderms (dermal bones) of estuarine crocodiles, exposed to lead ammunition in food from the hunting activities of traditional Aboriginal owners, were sampled at two sites in Kakadu National Park, northern Australia. PIXE analyses showed enhanced, but relatively constant, ratios of Pb/Ca in the annual laminations. This was consistent with both their history of long term exposure to elevated anthropogenic Pb sources and the hypothesis that the osteoderm can be used as an archive of the crocodile's exposure to Pb during its life.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 05/2002; 190(s 1–4):439–444. · 1.27 Impact Factor
[show abstract][hide abstract] ABSTRACT: The heavy ion microprobe at the Australian Nuclear Science and Technology Organisation is capable of focussing heavy ions with an ME/q2 of up to 100 amu MeV. This makes the microprobe ideally suited for heavy ion elastic recoil detection analysis (ERDA). However, beam currents on a microprobe are usually very small, which requires a detection system with a large solid angle. We apply microbeam heavy ion ERDA using a large solid angle ΔE−E telescope with a gas ΔE detector to layered structures. We demonstrate the capability to measure oxygen and carbon with a lateral resolution of 20 μm, together with determination of the depth of the contamination in thin deposited layers.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2002; 190:301-305. · 1.27 Impact Factor
[show abstract][hide abstract] ABSTRACT: This paper describes PIXE/PIGE measurements on thin Micromatter Standard (±5%) foils run over a period of 10 years. The selected foils were typically 50 μg/cm2 thick and covered the commonly used PIXE X-ray energy range 1.4–20 keV and the light elements F and Na for PIGE studies. For the thousands of thick obsidian and pottery samples analysed over a 6-year period, the Ohio Red Clay standard has been used for both PIXE and PIGE calibration of a range of elements from Li to Rb. For PIXE, the long-term accuracy could be as low as ±1.6% for major elements with precision ranging from ±5% to ±10% depending on the elemental concentration. For PIGE, accuracies were around ±5% with precision ranging from ±5% in thick samples to ±15% in thin samples or for low yield γ-ray production.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2002; 189:81-85. · 1.27 Impact Factor
[show abstract][hide abstract] ABSTRACT: The heavy ion microprobe in combination with particle-induced X-ray emission was used to measure the distribution of manganese in freshwater mussel shells (Hyridella depressa) from the Nepean river in south-eastern Australia. Close to the ventral edge, bands with an elevated manganese content have been detected. These are correlated with growth bands in the mussels containing increased amounts of organic material, relative to the calcium carbonate matrix. Calcium minima, which were correlated to the annual growth rings, were measured close to the umbo region of the shells.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms - NUCL INSTRUM METH PHYS RES B. 01/2001; 181(1):593-597.