A. J. Nunn

Bio: A. J. Nunn is an academic researcher from Los Alamos National Laboratory. The author has contributed to research in topics: Uranium & Isotope dilution. The author has an hindex of 5, co-authored 7 publications receiving 57 citations.

Uranium and Thorium Concentration and Isotopic Composition in Five Glass (BHVO-2G, BCR-2G, NKT-1G, T1-G, ATHO-G) and Two Powder (BHVO-2, BCR-2) Reference Materials

Abstract: Here we report uranium and thorium isotopic ratios and elemental concentrations measured in solid reference materials from the USGS (BHVO-2G, BCR-2G, NKT-1G), as well as those from the MPI-DING series (T1-G, ATHO-G). Specifically created for microanalysis, these naturally-sourced glasses were fused from rock powders. They cover a range of compositions, elemental concentrations and expected isotopic ratios. The U-Th isotopic ratios of two powdered source materials (BCR-2, BHVO-2) were also characterised. These new measurements via multi-collector thermal ionisation mass spectrometry and multi-collector inductively coupled plasma-mass spectrometry can now be used to assess the relative performance of techniques and facilitate comparison of U-Th data amongst laboratories in the geoscience community for in situ and bulk analyses. Nous presentons ici les rapports isotopiques et les concentrations elementaires de l’uranium et du thorium mesures dans les materiaux de reference solides de l’USGS (BHVO-2G, BCR-2G, NKT-1G), ainsi que ceux de la serie MPI-DING (T1-G, ATHO-G). Specifiquement cree pour la microanalyse, ces materiaux de reference sont des verres d’origine naturelle qui ont ete fabriques par la fusion de poudres de roche. Ils couvrent une gamme prevue de compositions, de concentrations elementaires et de rapports isotopiques. Les rapports isotopiques U-Th de deux materiaux de base reduits en poudre (BCR-2, BHVO-2) ont egalement ete caracterises. Ces nouvelles mesures obtenues en utilisant les techniques de spectrometrie de masse a ionisation thermique et a multi-collection (MC-TIMS) et de spectrometrie de masse a source plasma et a multi-collection (MC-ICP-MS) peuvent etre maintenant utilise pour evaluer la performance relative des techniques et pour faciliter la comparaison des donnees U- Th in situ et globales entre les laboratoires de la communaute des geosciences pour des analyses in situ et en vrac.

Evaluation of new geological reference materials for uranium-series measurements: Chinese Geological Standard Glasses (CGSG) and macusanite obsidian.

Abstract: Recent advances in high-resolution, rapid, in situ microanalytical techniques present numerous opportunities for the analytical community, provided accurately characterized reference materials are available. Here, we present multicollector thermal ionization mass spectrometry (MC-TIMS) and multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) uranium and thorium concentration and isotopic data obtained by isotope dilution for a suite of newly available Chinese Geological Standard Glasses (CGSG) designed for microanalysis. These glasses exhibit a range of compositions including basalt, syenite, andesite, and a soil. Uranium concentrations for these glasses range from ∼2 to 14 μg g–1, Th/U weight ratios range from ∼4 to 6, 234U/238U activity ratios range from 0.93 to 1.02, and 230Th/238U activity ratios range from 0.98 to 1.12. Uranium and thorium concentration and isotopic data are also presented for a rhyolitic obsidian from Macusani, SE Peru (macusanite). This glass can also be used as ...

Sequential chemical separations and multiple ion counting ICP-MS for 241Pu–241Am–237Np dating of environmental collections on a single aliquot

Abstract: We have developed a combined sequential chemical separation procedure and multiple ion counting ICP-MS measurement method for isotopic measurements of Am in environmental samples. This, in conjunction with established resin bead TIMS measurements for Pu and Np, allows us to measure long-lived Pu–Np–Am nuclides in environmental samples on a single solution aliquot. This single aliquot method reduces time lines and maximizes sample utility for the measurements, improving sensitivity, precision, and accuracy over prior methods. We have evaluated this new method with environmental reference materials and have obtained accurate results on samples with > 3E6 atoms 241Am.

Atomic spectrometry update – a review of advances in environmental analysis

Abstract: This is the 30th annual review of the application of atomic spectrometry to the chemical analysis of environmental samples. This Update refers to papers published approximately between August 2013 and July 2014 and continues the series of Atomic Spectrometry Updates (ASUs) in environmental analysis that should be read in conjunction with other related ASUs in the series, namely: clinical and biological materials, foods and beverages, advances in atomic spectrometry and related techniques, elemental speciation,X-ray fluorescence spectrometry, and the analysis of metals, chemicals and functional materials. In the field of air analysis, highlights within this review period included: the use of 3D printing technology for the rapid prototyping of new air sampler components; single particle ICP-MS studies; use of a new triple-quadrupole ICP-MS for the analysis of radioactive species and the use of FEG-SEM and IBA for the analysis of gun-shot residues. In the field of water analysis, methods continue to be developed: for the extraction and preconcentration of elements; speciation of As, Cr, Hg and Sb forms and determination of elemental constituents in colloidal and NP fractions. Instrumental developments reported include the use of MC-ICP-MS for isotopic tracer studies and a review of XRF techniques and associated preconcentration procedures for trace element analysis. Many articles featuring the analysis of plants and soils appeared but, as usual, most focused on environmental applications rather than the advancement of atomic spectrometry. There have, however, been interesting developments, such as the almost bewildering increase in types of micro-extraction for analyte preconcentration and the resurgence of CS-AAS. Clearly LIBS is maturing rapidly, with soil analysis becoming more routine in nature. Also notable was the way the accident at the Fukishima-Daiichi nuclear power plant triggered development of analytical methods for the assessment of contamination in the surrounding area. Recent research indicates that geological applications still drives many of the instrumental and methodological advances in LA-ICP-MS. Fundamental studies continue to shed light on the processes involved and hence ways of improving the analysis of laser-produced aerosols. The preparation of NP powders for the production of matrix-matched RMs for microanalytical techniques such as LA-ICP-MS and SIMS showed great promise for addressing one of the major issues when analysing geological materials by these techniques. Steady advances in MC-ICP-MS methodology is feeding through to applications in isotope geochemistry, while new SIMS instrumentation is being directed towards probing fine growth structures in biogenic carbonates and inferring past climate conditions from their geochemistry. Feedback on this review is most welcome and the review coordinator can be contacted using the email address provided.

GSD-1G and MPI-DING Reference Glasses for In Situ and Bulk Isotopic Determination

Abstract: This paper contains the results of an extensive isotopic study of United States Geological Survey GSD-1G and MPI-DING reference glasses. Thirteen different laboratories were involved using high-precision bulk (TIMS, MC-ICP-MS) and microanalytical (LA-MC-ICP-MS, LA-ICP-MS) techniques. Detailed studies were performed to demonstrate the large-scale and small-scale homogeneity of the reference glasses. Together with previously published isotopic data from ten other laboratories, preliminary reference and information values as well as their uncertainties at the 95% confidence level were determined for H, O, Li, B, Si, Ca, Sr, Nd, Hf, Pb, Th and U isotopes using the recommendations of the International Association of Geoanalysts for certification of reference materials. Our results indicate that GSD-1G and the MPI-DING glasses are suitable reference materials for microanalytical and bulk analytical purposes.

Lead isotope analysis of melt inclusions by LA-MC-ICP-MS

Abstract: Pb isotope compositions of melt inclusions provide unique information about the composition of primary magmas and their source In this study, we have developed a method for measuring Pb isotopes in small olivine-hosted melt inclusions (>40 μm) from young and old volcanoes by LA-MC-ICP-MS We used a new interface cone assemblage consisting of a Jet sample cone and X skimmer cone A small flow of N2 gas was added to the carrier gas and passed through the assemblage to enhance the signal intensity In addition the energy and repetition rate of the laser conditions were reduced and the signal integration time was shortened in order to lengthen the laser ablation time and to collect enough data Mass bias and instrument drift were corrected using a standard–sample–standard bracketing method The analysis routine employed eight ion counters to receive 238U, 235U, 232Th, 208Pb, 207Pb, 206Pb, 204Pb and 202Hg signals simultaneously, which allowed Hg interference to be corrected on 204Pb, and in old samples U–Th decay to be age-corrected Using the Jet and X cones, under the same laser ablation conditions, the precisions for almost all the measured standard glasses are improved by at least a factor of two compared to using standard cones At 208Pb signal intensity >200 000 cps, external precisions of ratios involving 204Pb are better than 13% (2RSD) and precisions of 208Pb/206Pb and 207Pb/206Pb are better than 023% (2RSD) The results of Pb isotopes in olivine-hosted melt inclusions, using 45 μm laser spots, show that the internal precisions of 208Pb/206Pb and 207Pb/206Pb for most analyzed melt inclusions are better than 02% (2RSE) and for ratios involving 204Pb are better than 08% (2RSE) We are able to present the first ever Pb isotope data from ∼260 Ma Emeishan flood basalt olivine-hosted melt inclusions They show the importance to do age correction which results in the reduction of the spread of data in old samples The mean values of age-corrected 208Pb/206Pb and 207Pb/206Pb have 12% and 28% deviations from the uncorrected mean values, respectively The method developed here provides a fast, precise and accurate in situ Pb isotopic composition analysis, applicable not only to melt inclusions from young basalts, but also from old samples that require correction for U–Th decay