Wavelength-dispersive Electron Microprobe Research Articles

Speciation of PM10 Sources of Airborne Nonferrous Metals within the 3-km Zone of Lead/Zinc Smelters

The purpose of this study was to estimate the speciation of PM10 sources of airborne Pb, Zn, and Cd metals (PM10 is an aerosol standard of aerodynamic diameter less than 10 microm.) in the atmosphere of a 3 km zone surrounding lead/zinc facilities in operation for a century. Many powdered samples were collected in stacks of working units (grilling, furnace, and refinery), outdoor storages (ores, recycled materials), surrounding waste slag (4 Mt), and polluted topsoils (3 km). PM10 samples were generated from the raw powders by using artificial resuspension and collection devices. The bulk PM10 multielemental analyses were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The proportions in mass of Pb (50%), Zn (40%), and Cd (1%) contents and associated metals (traces) reach the proportions of corresponding raw powdered samples of ores, recycled materials, and fumesize emissions of plants without specific enrichment. In contrast, Pb (8%) and Zn (15%) contents of PM10 of slag deposit were found to be markedly higher than those of raw dust, Pb (4%), and Zn (9%), respectively. In the same way, Pb (0.18%), Zn (0.20%), and Cd (0.004%) were enriched by 1.7, 2.1, and 2.3 times, respectively, in PM10 as compared with raw top-soil corresponding values. X-ray wavelength dispersive electron-microprobe (EM-WDS) microanalysis did not indicate well-defined phases or simple stoichiometries of all the PM10 samples atthe level of the spatial resolution (1 microm3). X-ray photoelectron spectroscopy (XPS) indicated that minor elements such as Cd, Hg, and C are more concentrated on the particle surface than in the bulk of PM10 generated by the smelting processes. (XPS) provided also the average speciation of the surface of PM10; Pb is mainly represented as PbSO4, Zn as ZnS, and Cd as CdS or CdSO4, and small amounts of coke were also detected. The speciation of bulk PM10 crystallized compounds was deduced from XRD diffractograms with a raw estimation of the relative quantities. PbS and ZnS were found to be the major phases in PM10 generated by the smelting facilities with PbSO4, PbSO4 x PbO, PbSO4 x 4PbO, Pb metal, and ZnO as minor phases. The slag waste PM10 was found to contain some amounts of PbCO3, PbSO4 x PbO, and ZnFe2O4 phases. The large heterogeneity at the level of the individual particle generates severe overlap of chemical information even at the microm scale using electron microprobe (WDS) and Raman microprobe techniques. Fortunately, scanning Raman microspectrometry combined with SIMPle-to-use Interactive Self-modeling Mixture Analysis (SIMPLISMA) performed the PM10 speciation at the level of individual particles. The speciation of major Pb, Zn, and Cd compounds of PM10 stack emissions and wind blown dust of ores and recycled materials were found to be PbSO4, PbSO4 x PbO, PbSO4 x 4PbO, PbO, metallic Pb, ZnS, ZnO, and CdS. The PM10 dust of slag waste was found to contain PbCO3, Pb(OH)2 x 2PbCO3, PbSO4 x PbO, and ZnS, while PM10-bound Pb, Zn of the top-soils contain Pb5(PO4)3Cl, ZnFe2O4 as well as Pb(II) and Zn(II) compounds adsorbed on Fe(III) oxides and in association with clays.

Model independent phase equilibrium constraints on the ferrosilite activity in the binary Fe-Mg orthopyroxene solid solution

Compositional reversals of orthopyroxene solid solution (Opx) on the enstatite (En, MgSiO 3 )-ferrosilite (Fs, FeSiO 3 ) join equilibrated with hematite (Hm, Fe 2 O 3 ), magnetite (Mt, Fe 3 O 4 ), and quartz (Qz) were obtained in piston-cylinder apparatus in the pressure range 10–25 kbar at temperatures of 800 and 950 °C. A double-capsule technique with the Hm-Mt external buffer was employed to ensure the presence of both Fe oxides in the run products. Starting materials were crystalline mixtures of synthetic Opx with X Fs [=Fe/(Fe+Mg)] = 0.05 and 0.45, reagent Mt, Hm, and natural Qz. Run products were carefully examined using optical microscopy, back-scattered (BSE) imaging, and wavelength dispersive electron microprobe analysis. Despite the differences in the rates of forward and backward reactions Fs (in Opx) + Hm = Mt + Qz (1), very tight compositional brackets (less than 0.01 X Fs ) were obtained at each P - T . At 800 °C, midpoints of the compositional brackets are: 0.195/10 kbar, 0.24/15, 0.29/20, and 0.34/25; at 950 °C: 0.21/15 kbar, 0.25/20, and 0.295/25 kbar. Activities of Fs, recalculated from these compositions using either Berman and Aranovich (1996) or Holland and Powell (1998) data sets for the pure end-member reaction (1), show negative deviation from ideal mixing. Strongly temperature dependent enthalpy of mixing is required to make these activity values consistent with the configurational entropy of the solid solution deduced from the site occupancy measurements. A simple mixing model with a linearly varying temperature-dependent W term, similar to that of Berman and Aranovich (1996), adequately reproduces the experimental data.

Understanding Bronze Age Faience in Britain and Ireland

ABSTRACTAround 350 Bronze Age faience beads and pendants are known from Britain and Ireland, mostly from burials of cremated human bone. Their relationship with Near Eastern and Mediterranean faience has long been debated. A National Museums of Scotland (NMS) led international research project is investigating their origin, composition, manufacture and use (inter alia) for aCorpusof faience from Britain, Ireland and adjacent parts of mainland Europe. Non-destructive controlled-pressure scanning electron microscopy with energy dispersive microanalysis (CP-SEM-EDS), X-ray fluorescence (XRF) and binocular microscopy provide compositional and textural information without sampling or coating. Wavelength-dispersive electron microprobe (EMP) analysis of rare polished samples provides additional and more accurate compositional information. The results demonstrate that direct derivation from Egyptian or Mediterranean faience traditions can be ruled out. The beads and pendants were manufactured on a small-scale basis, using mostly a mixed alkali paste and glaze from plant ash sources (including seaweed) and a copper-based glaze colorant probably derived from bronze. Tin (or its oxide) seems to have been deliberately added. Various forming and glazing techniques were used. We have demonstrated, for the first time, that some beads were worn during cremation; and we have further investigated the effects of cremation on faience by experimentally cremating a pig wearing a newly-made faience necklace.

Optimization of Wavelength Dispersive X-Ray Spectrometry Analysis Conditions.

In setting up the conditions for quantitative wavelength-dispersive electron microprobe analysis a number of parameters have to be defined for each element, namely accelerating voltage, beam current, and (for each element) x-ray line, spectrometer crystal, pulse-height analyser settings, background offsets, and counting times for peak and background. The choices made affect both the reliability of the results and the time taken to obtain a complete analysis. It is difficult for even an experienced user to arrive at the optimum set of conditions for any particular application, in view of the large number of interacting factors involved. Furthermore, optimum choices of some parameters are dependent not only on the concentration of the element concerned (for example, counting times) but also the concentrations of other elements which may have peaks that interfere with peak and/or background measurements, requiring alternative selections of x-ray line or spectrometer crystal. The various factors involved in arriving at an optimum routine and practical possibilities for computer-aided optimization are discussed here.

Authigenic Apatite in a Fluvial Sandstone Sequence: Evidence for Rare-Earth Element Mobility During Diagenesis and a Tool for Diagenetic Correlation

ABSTRACT Apatite grains in heavy-mineral separates of samples from the Statfjord Formation (Triassic-Lower Jurassic, North Sea), exhibit variably corroded detrital cores and euhedral diagenetic overgrowths. In the overlying marine deposits of the Nansen Formation, apatite grains show no evidence of either corrosion or overgrowths. Compositions of detrital apatite in both formations are indistinguishable, indicating that the source areas responsible for Statfjord and Nansen deposition included similar apatite-bearing lithologies. Apatite corrosion in the Statfjord Formation is considered to be a response to leaching by acidic groundwaters during sediment storage on the fluvial floodplain. Any variations in the degree of corrosion that may have been generated by differences in floodplain residence time have been homogenized by sediment reworking. Laser-ablation microprobe inductively coupled plasma mass spectrometry and wavelength-dispersive electron microprobe analysis indicate that the authigenic apatite contains high abundances (up to 3.5% total) of the rare earth elements (REE), implying a degree of REE mobilization during diagenesis. REE profiles (NASC normalized) for the authigenic apatites are convex-upwards with enrichment of the MREE. The REE are considered to have been derived from dissolution of other REE-bearing heavy minerals (e.g., garnet) during alluvial storage, with possible contributions from dissolved feldspars (which may account for slight positive Eu anomalies) and REEs adsorbed onto clay surfaces. REE mobilization was probably enhanced by fluoride and/or phosphate complexes, although organic complexing related to pedogenic processes is also a possibility. Through the Statfjord Formation, authigenic apatite displays subtle variations in major-element, minor-element, and trace-element chemistry, which may find application as a tool for diagenetic correlation.

Population structure of sympatric anadromous and nonanadromousOncorhynchus mykiss: evidence from spawning surveys and otolith microchemistry

Reproductive isolation between steelhead and resident rainbow trout (Oncorhynchus mykiss) was examined in the Deschutes River, Oregon, through surveys of spawning timing and location. Otolith microchemistry was used to determine the occurrence of steelhead and resident rainbow trout progeny in the adult populations of steelhead and resident rainbow trout in the Deschutes River and in the Babine River, British Columbia. In the 3 years studied, steelhead spawning occurred from mid March through May and resident rainbow trout spawning occurred from mid March through August. The timing of 50% spawning was 9-10 weeks earlier for steelhead than for resident rainbow trout. Spawning sites selected by steelhead were in deeper water and had larger substrate than those selected by resident rainbow trout. Maternal origin was identified by comparing Sr/Ca ratios in the primordia and freshwater growth regions of the otolith with a wavelength-dispersive electron microprobe. In the Deschutes River, only steelhead of steelhead maternal origin and resident rainbow trout of resident rainbow trout origin were observed. In the Babine River, steelhead of resident rainbow trout origin and resident rainbow trout of steelhead maternal origin were also observed. Based on these findings, we suggest that steelhead and resident rainbow trout in the Deschutes River may constitute reproductively isolated populations.

Temperature-Dependent Fractionation of Particulate Matter and Sulfates from a Hot Flue Gas in Pressurized Pulverized Coal Combustion (PPCC)

The development of new highly efficient combined-cycle power plants is fundamentally linked to the development of new hot flue gas purification systems. Hot flue gas purification systems aim to remove particles and newly formed particulate matter from condensation reactions from the flue gas to prevent any damage to the gas turbine. This study focuses on the characterization of particulate matter which was deposited onto the inner walls of flue gas probes in a 1 MW pilot plant for pressurized pulverized coal combustion under slagging conditions (PPCC). The particulate matter in the flue gas stream originates from incompletely separated fly ash particles and particles formed during condensation processes from the hot flue gas. The phase analysis of the materials was done by high-resolution scanning electron microscopy. The combination of wavelength dispersive electron microprobe with a knowledge of the approximate temperature profile through the flue gas probe allowed the definition of dew points of single crystalline phases under the actual pressure conditions from the hot flue gas in the pilot plant. At high temperatures (> 1200 °C) the deposits on the inner wall of the flue gas probe are mainly fly ash particles which were deposited in the liquid state. With decreasing temperature, CaSO 4 , Na 2 SO 4 , K 2 Ca 2 (SO 4 ) 3 , and K 3 Na(SO 4 ) 2 condense from the flue gas. The ubiquitous occurrence of crystalline Cr 2 O 3 can be traced to high-temperature refractory materials in the boiler and the subsequent particle separator of the pilot plant. At low temperatures some sulfates may decompose and form highly corrosive pyrosulfate melts. The changes in the phase composition of the deposits correlate well with chemical profiles along the flue gas probe.

Variation in otolith strontium and calcium ratios as an indicator of life-history strategies of freshwater fish species within a brackish water system

A possible life-history strategy of freshwater fish in brackish waters would be one of migrations between higher salinity rearing/feeding areas and low salinity spawning areas. This would allow the more euryhaline adults and sub-adults a greater foraging range, while increasing the chance of survival of highly stenohaline eggs and larvae. We tested the feasibility of using the variation in otolith strontium/calcium ratios (Sr/Ca) as a method to investigate migrations of freshwater species living under oligo-mesohaline conditions. Zander ( Stizostedion lucioperca L.) and common bream ( Abramis brama L.) adults were collected in the brackish Kiel Canal and its largest free-flowing freshwater tributary, the Haaler Au. Furthermore, reference fish were obtained from a closed freshwater lake. Otoliths were thin sectioned and polished. Strontium and calcium concentrations were measured along transects between the otolith core and outside edge at approximately 10 μm intervals using a Cameca SX-50 wavelength dispersive electron microprobe. Strontium/calcium ratios found in the reference fish otoliths were fairly constant and low (common bream: x ̄ =0.0025, S.D.=0.0005 and zander: x ̄ =0.001, S.D.=0.0004). The Sr/Ca ratios in otoliths from brackish waters were more variable (common bream: x ̄ =0.0032, S.D.=0.0023 and zander: x ̄ =0.002, S.D.=0.001). Lowest Sr/Ca ratios were measured in core zones (<0.0003). Differences in patterns were observed, suggesting individual variations in migratory histories. Our results show that analysis of Sr/Ca has great potential for describing the migratory histories of freshwater fishes within brackish water systems.

Birefringence free planar optical waveguide made by flame hydrolysis deposition (FHD) through tailoring of the overcladding

Stresses developing in a planar waveguide resulting from the different thermal expansion coefficients of the substrate and the three glass layers (buffer, core and cladding) were analyzed using a finite element method. It can be shown that mainly the thermal expansion of the overcladding determines the birefringence in the finished waveguide. Based on that result, recipes for an overcladding made with the flame-hydrolysis-deposit ion (FHD)-process were devised. We demonstrate the absence of birefringence in a commercial waveguide layer overclad with this glass. The high doping levels required for the cladding to have a thermal expansion coefficient sufficient for this raises concerns about the moisture sensitivity of such a glass. We examined the depth dependent composition of the glass using WD-ESCA (wavelength dispersive electron microprobe) and show, that at the surface a layer depleted of dopants is formed during the high temperature sintering process, This layer can serve as a protective coating to isolate the underlying, higher doped layer from the effects of moisture. Analysis of the stresses shows that this does not effect the birefringence behavior of the waveguide.

Population structure of sympatric anadromous and nonanadromous &lt;i&gt;Oncorhynchus mykiss&lt;/i&gt;: evidence from spawning surveys and otolith microchemistry

Reproductive isolation between steelhead and resident rainbow trout (Oncorhynchus mykiss) was examined in the Deschutes River, Oregon, through surveys of spawning timing and location. Otolith microchemistry was used to de- termine the occurrence of steelhead and resident rainbow trout progeny in the adult populations of steelhead and resi - dent rainbow trout in the Deschutes River and in the Babine River, British Columbia. In the 3 years studied, steelhead spawning occurred from mid March through May and resident rainbow trout spawning occurred from mid March through August. The timing of 50% spawning was 9-10 weeks earlier for steelhead than for resident rainbow trout. Spawning sites selected by steelhead were in deeper water and had larger substrate than those selected by resident rain - bow trout. Maternal origin was identified by comparing Sr/Ca ratios in the primordia and freshwater growth regions of the otolith with a wavelength-dispersive electron microprobe. In the Deschutes River, only steelhead of steelhead mater - nal origin and resident rainbow trout of resident rainbow trout origin were observed. In the Babine River, steelhead of resident rainbow trout origin and resident rainbow trout of steelhead maternal origin were also observed. Based on these findings, we suggest that steelhead and resident rainbow trout in the Deschutes River may constitute reproduc- tively isolated populations.

Factors influencing otolith strontium/calcium ratios in Anguilla japonica elvers

The effects of temperature and salinity on the concentration ratios of strontium (Sr) to calcium (Ca) within the sagittal otoliths of elvers of the Japanese eel, Anguilla japonica, were studied by spot analysis using a wavelength dispersive X-ray electron microprobe. A total of 340 elvers were used: 100 elvers were reared for 15 days under various salinity conditions (freshwater, one-third seawater, two-thirds seawater and pure seawater at 22 °C; 240 elvers were reared for 58 days under various water temperature conditions (12, 17, 22, 27 °C) in either freshwater or pure seawater. Otolith Sr/Ca ratios were found to be positively correlated with water salinity. On the other hand, the Sr/Ca ratios were not found to be significantly different among the various temperature groups. The above results strongly suggest that the physiological mechanism of incorporation of Sr and Ca within the otolith of an eurythermal fish, Japanese eel, does not change within this range of temperatures (12–27 °C).

Microprobe analyses of anadromous Arctic charr, Salvelinus alpinus , otoliths to infer life history migration events

Otoliths of Arctic charr, Salvelinus alpinus, from north Labrador were examined to gather life history information pertinent to anadromous migrations. Wavelength dispersive electron microprobe measurements confirm the presence of strontium in otolith tissue. Trace element analyses of charr otoliths imply that otolith strontium/calcium concentration ratios are related to external environmental factors with salinity having a great influence. Otoliths clearly record habitat shifts consistent with migration across major salinity boundaries. Most charr first migrate to sea following at least 2 years in freshwater. Generally, when anadromy begins, it continues annually. Robust relationships in otolith chemistry, combined with macrostructure patterns in field-captured specimens, provide time-series data describing individual migrational histories. Validation studies are still required in order to couple information contained within daily increments with chemical analyses to infer additional temporal events in diadromous migrations.

Comparison of accuracy, precision, and sensitivity in elemental assays of fish otoliths using the electron microprobe, proton-induced X-ray emission, and laser ablation inductively coupled plasma mass spectrometry

The elemental composition of fish otoliths is of considerable interest to those who wish to reconstruct temperature, migration, or environmental histories of individual fish based on assays of the otolith growth sequence. However, reported differences in otolith elemental composition among studies may be due in part to performance differences among four of the most popular instruments for targeted elemental analysis: wavelength-dispersive electron microprobe (WD-EM), energy-dispersive electron microprobe (ED-EM), proton-induced X-ray emission (PIXE), and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). To rigorously compare the sensitivity, accuracy, and precision of these four analytical tools, the International Otolith Composition Experiment distributed blind-labelled real and artificial otoliths of known but varied elemental composition to eight laboratories for assay of 10 selected elements. No one instrument type was sensitive to each element, nor was any one instrument preferred for use in all assays. In general however, abundant elements such as Na and K could only be measured accurately with an electron microprobe, while the trace elements required PIXE or LA-ICPMS. Strontium could be measured with considerable accuracy and precision by WD-EM, PIXE, and LA-ICPMS. The presence of significant, and occasionally large, differences among laboratories suggests that comparisons among published studies should be made cautiously and only after appropriate calibration.

Migrations in an extreme northern population of Arctic charr Salvelinus alpinus:insights from otolith microchemistry

Growth and migrations of Arctic charr from a Norwegian Arctic lake system were examined using structural and chemical characteristics of their otoliths as indicators of physiological and habitat characteristics. Measurements of otolith strontium/calcium concentration ratios by wavelength dispersive electron microprobe clearly revealed salinity migrations and provided a life history profile for individual fish. There was wide range in the age at first seaward migration (4 to 13 yr; mean 6.7 yr). Sr/Ca concentration data were also used to determine that a few migratory charr occasionally abstained from seasonal migrations Microchemical techniques are an innovative approach to life history analysis when used in combination with structural analyses of otoliths from migratory flsh K E Y WORDS: Stront~um . Anadromy Norway Spitsbergen . Electron microprobe . Life history

Formation of a stress-induced chemical check in fish otoliths

The effect of physiological stress on the Sr/Ca, S/Ca, Na/Ca, and K/Ca ratios measured in the sagittae of Australian salmon Arripis trutta Bloch et Schneider, a marine percoid teleost, was determined for a group of fish trapped in a stream with a lower salinity and higher temperature than the adjacent sea. Abnormally low conditions factors for these fish, when compared with other extensive collections of Australian salmon, provided evidence that they stressed. Life-history transects of Sr/Ca, S/Ca, Na/Ca, and K/Ca ratios made with a wavelength dispersive electron microprobe showed that there were consistent changes in otolith trace chemistry at the otolith edge. Both the Sr/Ca and S/Ca ratios increased at the otolith edge, whereas the Na/Ca and K/Ca ratios decreased. Similar changes in otolith chemistry were not evident in Australian salmon collected in nearby marine habitats. The results indicate that stress, in a general sense, can result in the incorporation of increased levels of Sr in fish otoliths, and that it can also affect other trace element levels in a systematic manner. Stress can produce a recognizable chemical check on fish otoliths and these marks may be useful as natural markers for age validation and stock discrimination studies.

Solubility of Ca in superconducting La 2− xCa xCuO 4

The superconducting transition temperature T c was determined as a function of x for La 2- x Ca x CuO 4 compounds. Midpoints of susceptibility transitions rise with x from below 5 K at x=0.05 to near 17.5 K for x⩾9. The Ca content of the major phase was determined in several samples using a calibrated wavelength dispersive electron microprobe. For nominal Ca content x⩾0.10, T c and determined Ca content are independent of nominal x. X-ray diffraction diagrams for samples with nominal x⩾0.12 show peaks indicative of additional phases. These findings are consistent with a Ca solubility limit near x=0.10. The pressure dependence of T c below 20 kbar was determined for one sample with nominal Ca content x=0.15 (analyzed x=0.12±0.02).

The geochemistry and cryptic zonation of pyrochlore from San Vicente, Cape Verde Islands

AbstractZr-rich pyrochlore crystals in carbonatite from San Vicente (Cape Verdes Islands) show cryptic, concentric and rhythmic chemical zonation with Ca increasing and Ti, U and Zr decreasing towards the rims. In one carbonatite, taken from the Camile dyke, previously undocumented cryptic sector zonation of Ti, U and Zr is also observed in these crystals. The chemical variation is investigated by wavelength-dispersive electron microprobe, with both single spot and crystal map analyses.The concentric and rhythmic zonation, marked by element substitution, was generated by magma heterogeneity and/or element diffusion kinetics, but it is suggested that the sector zonation, marked by differential site substitution, was governed by protosite variation between octahedral and cubic faces.

Combined energy‐dispersive–wavelength‐dispersive quantitative electron microprobe analysis

AbstractAn empirical study of the precision of measurement by energy‐dispersive (EDS) and wavelength‐dispersive (WDS) techniques is described. Combined EDS–WDS quantitative analysis provides efficient instrument operation, optimum precision in major element analysis and the best limits of detection in trace element analysis. A software package for a combination EDS–WDS electron microprobe is described.

DATING ROCK VARNISHES BY THE CATION RATIO METHOD WITH PIXE, ICP, AND THE ELECTRON MICROPROBE

The measurement of rock varnish cation-ratios [(K+Ca)/Ti] and barium is evaluated by analyzing the same varnish scrapings with PIXE, inductively coupled plasma, neutron activation and wavelength dispersive electron microprobe. Results among these different methods are generally similar for ratios, but absolute concentrations differ in part due to uncertainties associated with weighing small samples. Barium concentrations are typically less than 1 % by weight; higher concentrations can be found in varnishes with depressions eroded into the varnish by fungi and lichens, and later infilled with aeolian detritus often including barium sulfate. Since these infilled hollows are known to produce anomalous varnish cation ratios, high barium values can, therefore, be used as an indicator that a sample is inappropriate for cation-ratio dating. The glacial chronology at Pine Creek, California, is revised in light of new data and a better understanding of variables influencing varnish chemistry.

Strontium:cakium concentration ratios in otoliths of herring larvae as indicators of environmental histories

Elemental analyses, using wave-length dispersive electron microprobe techniques on otoliths from reared Atlantic herring larvae, Clupea harengus, showed trace quantities of strontium relative to that of calcium, and an inverse relationship between Sr/Ca concentration ratios and rearing temperature. These data are consistent with those for coral aragonite, in that there appears to be an inverse temperature effect on physiological incorporation of strontium in the otolith aragonite. Our determinations of Sr/Ca concentration ratios of lab-reared herring larvae showed that the deposition of strontium relative to calcium and the rearing temperature were related, where: T (° C) = −2.955 [Sr/Ca] × 1000 ± 19.172. This principle thus makes it possible to use Sr/Ca concentration ratios in fish otoliths to delineate past temperatures experienced by an individual. Further, combining electron microprobe analyses with scanning electron microscope (SEM) examinations of daily increments in the same otolith makes it possible to reconstruct the temperature history for an individual fish on a time scale of days. An example of the application of the technique to an approximately six-month-old field-caught herring larva is given, and the limitations of the technique are discussed.