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Lead (Pb) isotopic compositions and concentrations, and barium (Ba) and indium (In) concentrations have been analysed at sub-annual resolution in three sections from a110 m ice core dated to the 18th and 20th centuries, as well as snow pit samples dated to 2004/2005, recovered from the East Rongbuk Glacier in the high-altitude Himalayas. Ice core sections indicate that atmospheric chemistry prior to ~1,953 was controlled by mineral dust inputs, with no discernible volcanic or anthropogenic contributions. Eighteenth century monsoon ice core chemistry is indicative of dominant contributions from local Himalayan sources; non-monsoon ice core chemistry is linked to contributions from local (Himalayan), regional (Indian/Thar Desert) and long-range (North Africa, Central Asia) sources. Twentieth century monsoon and non-monsoon ice core data demonstrate similar seasonal sources of mineral dust, however with a transition to less-radiogenic isotopic signatures that suggests local and regional climate/environmental change. The snow pit record demonstrates natural and anthropogenic contributions during both seasons, with increased anthropogenic influence during non-monsoon times. Monsoon anthropogenic inputs are most likely sourced to South/South-East Asia and/or India, whereas non-monsoon anthropogenic inputs are most likely sourced to India and Central Asia.

Lead (Pb) isotopic compositions and concentrations, and barium (Ba) and indium (In) concentrations have been determined at monthly resolution in five Law Dome (coastal Eastern Antarctica) ice core sections dated from ∼1757 AD to ∼1898 AD. ‘Natural’ background Pb concentrations in ∼1757 AD average ∼0.2 pg g−1 and can be attributed to mineral dust and volcanic emissions, with 206Pb/207Pb ratios reaching up to 1.266 ± 0.002. From ∼1887 AD to ∼1898 AD, Pb concentrations reached ∼5 pg g−1 and 206Pb/207Pb ratios decreased to 1.058 ± 0.001 as a result of additional inputs of Pb from anthropogenic sources. Seasonal variability in the late 1880s has been investigated by decoupling volcanic Pb from the total measured Pb concentrations, revealing spring and autumn maxima, and consistent winter minima, in anthropogenic Pb and mineral dust (Ba) concentrations. We link this variability to the annual cycle in the position and strength of the Antarctic Circumpolar Trough and, the Southern Ocean westerly winds to the north of the trough region. During the autumn and spring seasons, these systems increase in strength, transporting more impurity laden air from the Southern Hemisphere continental regions to Eastern Antarctica and Law Dome. As this Pb is isotopically identical to that emitted from south-eastern Australia (Broken Hill, Port Pirie) this implies a relatively direct air trajectory pathway from southern Australia to Law Dome (Eastern Antarctica).

International audience; We present here a time series of Pb and Sr isotopes in Greenland ice over the last glacial cycle. The data were obtained by analysing the dust contained in small (less than 10 g) aliquots of sections of the GRIP (European Greenland ice core project) ice core. The concentrations of Pb, Ba and Sr vary by large factors of 70, 140 and 75 respectively over this time period and show a significant correlation with δ18O, used as a proxy for temperature. Elemental ratios of Pb, Ba and Sr indicate the provenance of dust is mainly crustal with possible volcanic influences but the contribution from seawater is negligible. The Pb and Sr isotopic ratios change over time and form two distinct groups above and below a temperature corresponding to a δ18O value of − 39‰. While changing elemental concentrations may be explained by changes in wind strengths, the variation in isotopic composition appears to reflect climate induced changes in the source areas of dust deposited in the snow in Greenland. Available source data suggest that dust may originate from the Gobi Desert in central Asia in cooler periods and from glacial sediments adjacent to Greenland in warmer periods.

Southern Ocean aerosols were collected at the Cape Grim Baseline Air Pollution Station from onshore air under baseline conditions between February 1999 and April 2000. Thermal ionization techniques (TIMS) and isotope dilution mass spectrometry (IDMS) were used to measure the isotopic composition and concentration of lead in the air giving concentrations as low as 0.6 ± 0.1 pg · m−3. Air collected under baseline conditions for 12 months (May 1999–April 2000) yielded an overall lead concentration of 11.0 ± 0.2 pg · m−3 and isotopic composition of 206Pb/207Pb = 1.154, 208Pb/207Pb = 2.387 and 206Pb/204Pb = 17.93. The range in isotopic ratios was consistent with the mixing of lead from major population centers in the Southern Hemisphere in the mid to high latitudes, except for the presence of highly radiogenic lead in some samples. Contributions from radiogenic lead of up to ∼0.8% were observed. Three periods with the highest percentage contribution of radiogenic lead (>0.5%) were investigated in more detail, and 4-d back-trajectories and radon concentrations were used to help identify the sources. The sources are probably associated with the mining and processing of uranium rich ores in southern Africa and possibly South Australia.

Experiments have been conducted to evaluate the potential of the BIGDIFF Debye–Scherrer diffractometer (radius of 573 mm) for characterizing ceramic materials using synchrotron radiation. The instrument has been tested at a wavelength of 0.1538 nm (1.5378), under in vacuo conditions, with standard reference materials and an alumina-matrix ceramic specimen using capillary-mounted (diameter of 0.5 mm) powdered material. The diffraction patterns that have been recorded with imaging plates over a period of 15 min provide phase detectability that is clearly superior to Bragg-Brentano laboratory X-ray diffractometry data that is collected in 1 h. The superiority of BIGDIFF for the analysis of phase composition becomes very pronounced for trace phases (,1%). The sharper definition of the Bragg peaks with BIGDIFF synchrotron radiation data also leads to improved estimates of nonlinear residual strain and crystallite size data. The superior performance of BIGDIFF is principally due to (i) the intensity of the synchrotron radiation incident beam that is achieved with high collimation and monochromaticity (E/ΔE 104), (ii) the large ratio of the camera radius to the capillary radius, and (iii) the spatial resolution and dynamic range of the imaging plates.

Strontium isotopic composition and concentration have been measured by thermal ionisation mass spectrometry on a suite of samples from the GRIP ice core drilled at Summit, Greenland. The sample ages range from ∼24 to ∼7.3 ky BP extending from the last glacial maximum into the early Holocene. Less than 10 g of sample was used for each analysis. No attempt was made to separate soluble/insoluble species in the samples. Sr concentrations are between ∼950 and ∼1,550 pg.g -1 over the period ∼24 ky to -14 ky BP but fall dramatically to generally less than 150 pg.g -1 between -14 to ∼7.3 ky BP. The 87 Sr/ 86 Sr ratio shows a general rising trend from ∼0.712 to ∼0.715 over the entire period however there are a number of significant deviations from this trend which are most likely due to changing source regions for aerosol dust input to Greenland. Sr isotopic composition shows a strong correlation with δ 18 O suggesting that climate plays a strong role in determining regions for dust release.

Techniques have been developed to measure the isotopic composition and concentration of Sr at sub-nanogram per gram levels in polar snow and ice samples. A 84 Sr spike was used to determine Sr concentrations on a single sample aliquot of a few millilitre. Microlitre scale columns of Sr-Spec resin were used to purify Sr samples. Thermal ionisation mass spectrometry (TIMS) was used to measure the Sr isotopic ratios. A single TIMS measurement of the Sr sample yielded both isotopic composition and concentration after deconvolution of spike and sample spectra. This allows isotopic variations in Sr to be used to identify source regions of crustal dust. Early Holocene and last glacial maximum ice core samples from both Antarctica and Greenland were analysed to demonstrate the applicability of the technique. Sr isotopes were analysed in ∼20 g sized samples of Antarctic early Holocene ice where the concentration was only ∼31 pg g−1. This represents an improvement of two orders of magnitude in sample consumption over previous studies allowing for a much higher time resolution in the analysis of polar ice cores.

A study has been conducted on the microstructural character, phase assemblage, and selected physical properties of liquid-phase-sintered (LPS) aluminas processed from formulations containing β-spodumene, Li2O·Al2O3·4SiO2. Assessments were made using density data, SEM imaging, XRD analysis, Vickers indentation testing, and Young's modulus measurements. The results indicate that using β-spodumene to develop LPS alumina ceramics provides materials containing a mix of crystalline β-spodumene and glassy material which are comparable in mechanical performance to currently available commercial debased alumina ceramics.

A study has been conducted on the microstructural character, phase assemblage, and selected physical properties of liquid-phase-sintered (LPS) aluminas processed from formulations containing β-spodumene, Li2O·Al2O3·4SiO2. Assessments were made using density data, SEM imaging, XRD analysis, Vickers indentation testing, and Young's modulus measurements. The results indicate that using β-spodumene to develop LPS alumina ceramics provides materials containing a mix of crystalline β-spodumene and glassy material which are comparable in mechanical performance to currently available commercial debased alumina ceramics.

International audience; A record of Pb isotopic compositions and Pb and Ba concentrations are presented for the EPICA Dome C ice core covering the past 220 ky, indicating the characteristics of dust and volcanic Pb deposition in central East Antarctica. Lead isotopic compositions are also reported in a suite of soil and loess samples from the Southern Hemisphere (Australia, Southern Africa, Southern South America, New Zealand, Antarctica) in order to evaluate the provenance of dust present in Antarctic ice. Lead isotopic compositions in Dome C ice support the contention that Southern South America was an important source of dust in Antarctica during the last two glacial maxima, and furthermore suggest occasional dust contributions from local Antarctic sources. The isotopic signature of Pb in Antarctic ice is altered by the presence of volcanic Pb, inhibiting the evaluation of glacial–interglacial changes in dust sources and the evaluation of Australia as a source of dust to Antarctica. Consequently, an accurate evaluation of the predominant source(s) of Antarctic dust can only be obtained from glacial maxima, when dust-Pb concentrations were greatest. These data confirm that volcanic Pb is present throughout Antarctica and is emitted in a physical phase that is free from Ba, while dust Pb is transported within a matrix containing Ba and other crustal elements.

Measurements of Pb isotope ratios in ice containing sub-pg g(-1) concentrations are easily compromised by contamination, particularly where limited sample is available. Improved techniques are essential if Antarctic ice cores are to be analysed with sufficient spatial resolution to reveal seasonal variations due to climate. This was achieved here by using stainless steel chisels and saws and strict protocols in an ultra-clean cold room to decontaminate and section ice cores. Artificial ice cores, prepared from high purity water were used to develop and refine the procedures and quantify blanks. Ba and In, two other important elements present at pg g(-1) and fg g(-1) concentrations in Polar ice, were also measured. The final blank amounted to 0.2+/-0.2 pg of Pb with (206)Pb/(207)Pb and (208)Pb/(207)Pb ratios of 1.16+/-0.12 and 2.35+/-0.16, respectively, 1.5+/-0.4 pg of Ba and 0.6+/-2.0 fg of In, most of which probably originates from abrasion of the steel saws by the ice. The procedure was demonstrated on a Holocene Antarctic ice core section and was shown to contribute blanks of only approximately 5%, approximately 14% and approximately 0.8% to monthly resolved samples with respective Pb, Ba and In concentrations of 0.12 pg g(-1), 0.3 pg g(-1) and 2.3 fg g(-1). Uncertainties in the Pb isotopic ratio measurements were degraded by only approximately 0.2%.