Core Community Specifications for Electron Microprobe Operating Systems: Software, Quality Control, and Data Management Issues

Modem electron microprobe systems have become increasingly sophisticated. These systems utilize either UNIX or PC computer systems for measurement, automation, and data reduction. These systems have undergone major improvements in processing, storage, display, and communications, due to increased capabilities of hardware and software. Instrument specifications are typically utilized at the time of purchase and concentrate on hardware performance. The microanalysis community includes analysts, researchers, software developers, and manufacturers, who could benefit from exchange of ideas and the ultimate development of core community specifications (CCS) for hardware and software components of microprobe instrumentation and operating systems

Quantifying heavy metals sequestration by sulfate-reducing bacteria in an acid mine drainage-contaminated natural wetland

Bioremediation strategies that depend on bacterial sulfate reduction for heavy metals remediation harness the reactivity of these metals with biogenic aqueous sulfide. Quantitative knowledge of the degree to which specific toxic metals are partitioned into various sulfide, oxide, or other phases is important for predicting the long-term mobility of these metals under environmental conditions. Here we report the quantitative partitioning into sedimentary biogenic sulfides of a suite of metals and metalloids associated with acid mine drainage contamination of a natural estuarine wetland for over a century

Tourmaline Reference Materials for the In Situ Analysis of Oxygen and Lithium Isotope Ratio Compositions

Three tourmaline reference materials sourced from the Harvard Mineralogical and Geological Museum (schorl 112566, dravite 108796 and elbaite 98144), which are already widely used for the calibration of in situ boron isotope measurements, are characterised here for their oxygen and lithium isotope compositions. Homogeneity tests by secondary ion mass spectrometry (SIMS) showed that at sub‐nanogram test portion masses their 18O/16O and 7Li/6Li isotope ratios are constant within ± 0.27‰ and ± 2.2‰ (1s), respectively. The lithium mass fractions of the three materials vary over three orders of magnitude. SIMS homogeneity tests showed variations in 7Li/28Si between 8% and 14% (1s), which provides a measure of the heterogeneity of the Li contents in these three materials. Here we provide recommended values for δ18O, Δ’17O and δ7Li for the three Harvard tourmaline reference materials based on results from bulk mineral analyses from multiple, independent laboratories using laser‐ and stepwise fluorination gas mass spectrometry (for O), and solution multi‐collector inductively coupled plasma‐mass spectroscopy (for Li). These bulk data also allow us to assess the degree of inter‐laboratory data that might be present in such datasets. This work also re‐evaluates the major element chemical composition of the materials by electron probe microanalysis and investigates the presence of a chemical matrix effect on SIMS instrumental mass fractionation with regards to δ18O determinations, which was found to be < 1.6‰ between these three materials. The final table presented here provides a summary of the isotope ratio values that we have determined for these three materials. Depending on their starting mass either 128 or 256 splits have been produced of each material, assuring their availability for many years into the future

Low voltage EPMA: experiments on a new frontier in microanalysis - analytical lateral resolution

Field emission (FE) electron gun sources provide new capabilities for high lateral resolution EPMA. The determination of analytical lateral resolution is not as straightforward as that for electron microscopy imaging. Results from two sets of experiments to determine the actual lateral resolution for accurate EPMA are presented for Kα X-ray lines of Si and Al and Lα of Fe at 5 and 7 keV in a silicate glass. These results are compared to theoretical predictions and Monte Carlo simulations of analytical lateral resolution. The experiments suggest little is gained in lateral resolution by dropping from 7 to 5 keV in EPMA of this silicate glass

Experiments with Low Voltage Field Emission EPMA

We report results from 5-7 keV Field Emission EPMA experiments on selected natural minerals and synthetic materials to illustrate some strengths -- and pitfalls --of low keV FE-EPMA. In a silicate mineral in pseudotachylite from South Mountain, AZ (Goodwin, 1999), the spatial resolution (equation of Merlet &amp; Llovet, 2012, with an 80 nm diameter beam) at 7 keV for Si Ka is calculated to be 588 nm, 391 nm for Ca Ka and 641 nm for Fe La. This pseudotachylite contains abundant 5-10 um sieve-textured crystals full of inclusions with low BSE intensity. Previous 15 keV work suggested the sieve phase was amphibole. At 7 keV, it is possible to identify the compositions of the submicron inclusions as SiO2 and a K-rich alumino-silicate phase; the host composition is epidote. The enhanced resolution of FE-EPMA reveals problems with some microanalytical standards. Vicenzi and Rose (2008) showed submicron inclusions in the Smithsonian Kakanui hornblende standard. Our 7 keV experiments show the ~400 nm inclusions consist of a silicate phase (glass?), Fe-Ti oxide and possibly a gas bubble, concentrated along planes or grain boundaries. SEM imaging of an inclusion analyzed with a focused FE beam shows radiating trails of debris on the hornblende host, consistent with residue from a popped vapor bubble in the inclusion. How should FE-EPMA handle standards that may have inclusions? Use a focused beam avoiding inclusions? Sometimes, perhaps. However, we used a defocused beam to "average" the phases. The results show little or no deviation from the published wet chemical analysis. Operation at reduced keV may require use of non-traditional X-ray lines (e.g. Gopon et al, 2013 for Fe Ll vs Fe La). Experiments at 5 keV were also performed upon a synthetic material enriched in Nd (Nd-Mg-Zn). Fischer &amp; Baun (1967) demonstrated problems with the Ma/Mb lines of REE; we find that use of the Nd Mz line is necessary in order to achieve reasonable results in this material (98 wt% total, Nd 36 wt% vs 126 wt% total, Nd 67 wt% with Mb line). We also report on 7 and 15 keV time dependent intensity variations in Ir-coated calcite and dolomite and on the lack of interfering lines with 6 Å Ir

Quantifying heavy metals sequestration by sulfate-reducing bacteria in an Acid mine drainage-contaminated natural wetland.

Bioremediation strategies that depend on bacterial sulfate reduction for heavy metals remediation harness the reactivity of these metals with biogenic aqueous sulfide. Quantitative knowledge of the degree to which specific toxic metals are partitioned into various sulfide, oxide, or other phases is important for predicting the long-term mobility of these metals under environmental conditions. Here we report the quantitative partitioning into sedimentary biogenic sulfides of a suite of metals and metalloids associated with acid mine drainage contamination of a natural estuarine wetland for over a century