Zdenek Nejedly

The Guelph PIXE software package III: Alternative proton database

Abstract A second X-ray production database is introduced into GUPIX to complement the existing theoretical (ECPSSR–DHS) database and to provide some estimate of analytical uncertainty due to this aspect of GUPIX; it is based on published compilations and analyses of large numbers of measured K and L subshell X-ray production cross-sections. The two databases are compared through analysis of single-element standards and standard reference materials. Good agreement is observed for the case of K X-rays. In contrast, neither the theoretical nor the “reference” database appears to be entirely satisfactory in the case of L X-rays. New work is required on L subshell X-ray production cross-sections using protons. The tools in GUPIX for film thickness determination are expanded, and tested using the two alternative databases.

The physical and chemical evolution of aerosols in smelter and power plant plumes: an airborne study

National and international concern about the health effects and continued use of Pb, Cd, As and Hg as well as other metals has defined a need for improved estimates of the long-term risks to ecosystems and human health from metals released from mining, metallurgical and energy production activities. A research aircraft was used to determine the microphysical and chemical properties of airborne particulate metal emissions from the Nanticoke coal-fired power-generating station located on the north shore of Lake Erie, Ontario, and the Horne copper smelter at Rouyn-Noranda, Quebec. These properties are critical to the determination of the deposition rates of the metals emitted, and hence the potential for these species to have impacts on local or distant ecosystems. An overview of the measurements made during the study is given. The size distributions of particles emitted from the stacks and observed within 5 km of the point of emission are briefly described. After dilution by ambient air, the concentration of particles smaller than 0.135 μm in diameter in the plumes is tens of thousands per cubic centimetre, far exceeding the concentrations found in ambient air. However, in the size range 0.135 to 3 μm diameter the plumes generally contribute about one to four times more particles than present in ambient air.

Extension of gupix to 2H, 3He and 4He excitation

Abstract The ionization and stopping power databases in gupix are extended to deal with deuterons and helium ions. The new databases are tested through analysis of standard reference materials using pure elemental targets as standards. Good accuracy is demonstrated for elements in a NIST steel reference material. Deficiencies in the L cross-section database are demonstrated through measurements on BCR standard gold films on nickel substrates.

Micro-PIXE analysis of trace element variation in otoliths from fish collected near acid mine tailings: Potential for monitoring contaminant dispersal

Abstract Otoliths from fish sampled proximal to acid mine tailings located near Sherridon, Manitoba contain elevated abundances of Zn, Mn, Fe and Cu. Sr is also present in amounts ranging from 250 to 1200 ppm with the actual levels dependent on the lake from which fish were taken. Previous work on analyzing Zn and Mn suggests Zn will typically vary between 50 and ∼100 ppm (in marine and non-marine species) and Mn between 10 and ∼100 ppm. Otoliths analyzed in this study contain up to ∼1000 ppm Zn and up to ∼400 ppm Mn; Fe is present, ranging between 50 and 100 ppm and Cu is typically 40–50 ppm. Water samples showed variation in these elements depending on proximity to the tailings.

Standardization of a micro-PIXE system using NIST iron- and nickel-based alloy reference materials

Abstract Five NIST standard reference Mo-bearing alloys are evaluated in the context of standardizing a micro-PIXE system that operates with a range of aluminum X-ray absorbers. The instrumental constant H is determined with accuracy of about 1% via the Mo content, and the absorber thickness is subsequently deduced via the Fe or Ni content. The influence of alloy heterogeneity is examined, and it is found necessary to raster the beam spot to compensate. The steel SRM C1296 is our choice for characterization when the absorber thickness is 300 μm or less. The Ni-based alloy SRM 1160 is suitable for absorbers in the range 300–500 μm.

Micro-PIXE analysis of strontium in Arctic char, Salvelinus alpinus, otoliths from Quttinirpaaq National Park, Nunavut, Canada

Abstract Arctic char, Salvelinus alpinus, exhibit either lake resident or anadromous (sea-run) life histories. Anadromy is less prevalent at the northern and southern extremes of the distribution. Effective conservation and management of char requires knowledge of life histories exhibited by individuals and populations. Micro-PIXE line-scans were used to determine the distribution of strontium (Sr) in otoliths from which life history patterns were determined for Arctic char from 10 lakes in Quttinirpaaq National Park in the Canadian High Arctic. Although most populations were lake resident as expected, the data indicated that a component of the char population from one lake was anadromous. This represents the most northerly known char population to exhibit anadromy. Mean Sr concentrations in otoliths of char from all populations, as determined by point analysis and also from line-scan data, showed no significant differences between the methods. Mean Sr concentrations (from point analysis) showed significant differences between some of the populations. These differences combined with other analyses (e.g. morphometrics, genetics) can be used to differentiate biological populations. Thus, micro-PIXE analysis is a useful tool for assessing diversity in Arctic char and contributing to their management and conservation in the park.

In-stack and in-plume characterization of particulate metals emitted from a copper smelter

To better understand the transport of particles emitted from industrial sources, a research aircraft was flown in the plume of the Horne Copper Smelter in Rouyn-Noranda, Quebec, during winter and summer of 2000. During seven flights the industry performed in-stack sampling for metals while the aircraft determined in-situ chemical and microphysical properties of the particles in the plume over distances of 2 to 27 km. The estimated dilution factors for the samples collected in the plume ranged from 2000 to 50 000 compared with in-stack samples. The ratios of As/Cu, Pb/Cu and Zn/Cu for the stack and in-plume samples show good correspondence. The relative fraction of As, Cu, Pb and Zn in the size bins <2 μm, 2–8 μm and >8 μm aerodynamic diameter were established using a cascade impactor in the plume. The As, Cu and Pb were found in larger fraction in the <2 μm size bin with Zn more equally distributed between the <2 and >8 μm bins. There was no evidence found to support preferential loss of the particles detected in the >8 μm bin over the distances studied. These data provide input needed to initialize models to predict the deposition and transport of the emissions.

Applications of PIXE to mineral characterization

Abstract This article illustrates the application of the proton-induced X-ray emission (PIXE) technique to detailed documentation of mineral assemblages, with emphasis on base–metal ores. Some of the investigations aided by the PIXE laboratory at Guelph since 1993 include determinations of the distribution of minor and trace elements in magmatic Ni–Cu ores, volcanogenic massive sulphide Cu–Pb–Zn–(Ag–Au) ores and lode Au–(Ag) deposits. Minor elements of importance include possible by-products or co-products of metal refining, as well as deleterious impurities in mill-feed, e.g. Cd, In, Sn, As, Se, Te, Tl and Hg. Weathering products of primary sulphide mineralization, including tropical laterites and other oxidized assemblages, have been analysed successfully and can contain a wide range of minor elements which reflect the bedrock style of mineralization. The iron oxyhydroxide goethite, α-FeO(OH), contains trace levels of many elements, and in some cases 1 wt.% or more of base metals and arsenic, elements which are invisible in reflected-light microscopy. Other metals such as Ag are of sporadic occurrence in oxidized ores: they may be found as discrete mineral species, not incorporated into the dominant oxyhydroxides. A summary of findings from three base–metal deposits in Canada, the Philippines and Portugal serves to illustrate the manner in which PIXE data benefit our knowledge of metal distributions in metallic ores. PIXE can contribute to several facets of mineral-deposit research, such as: (1) the development of ore textures, and specifically the distribution of elements within zoned crystals, or between multiple generations of a particular mineral; (2) the location of precious metals, Ag being in general the simplest case; and (3) pinpointing elements that may have implications for ore genesis, environmental quality or metal refining, such as Cr, As and Se.

Improvement in limit of detection in particle induced X-ray emission by means of rise time and pulse shape discrimination

A digital signal processor, based upon high-rate sampling of the preamplifier output, and equipped with rise time and pulse shape discrimination, has been tested in three situations. This processor provided significant improvement of particle induced X-ray emission and X-ray fluorescence detection limits over the state of the art analog processors, depending on the energy and intensity distribution of the X-ray spectra. Additionally it had a superior performance when measurements were performed in an environment of large electronic noise and in large nuclear background environment. It has also improved the reduction of several artifacts in X-ray spectra.

Improvement of detection limits of PIXE by substrate signal reduction

Abstract Limits of detection (LODs) for aerosol samples collected using PIXE International cascade impactors, were improved approximately 50% after reducing the cross-sectional area of the analytical beam based on results obtained from microscope photographs of aerosol deposits. Improvements in LODs were most noticeable for selected elements collected on the smaller stages of the impactor (stages 1–3).