The biennial review of atomic-weight determinations and other cognate data has resulted in changes for the standard atomic weights of 19 elements. The standard atomic weights of four elements have been revised based on recent determinations of isotopic abundances in natural terrestrial materials:

Abstract The biennial review of atomic-weight determinations and other cognate data has resulted in changes for the standard atomic weights of 19 elements. The standard atomic weights of four elements have been revised based on recent determinations of isotopic abundances in natural terrestrial materials: cadmium to 112.414(4) from 112.411(8), molybdenum to 95.95(1) from 95.96(2), selenium to 78.971(8) from 78.96(3), and thorium to 232.0377(4) from 232.038 06(2). The Commission on Isotopic Abundances and Atomic Weights (ciaaw.org) also revised the standard atomic weights of fifteen elements based on the 2012 Atomic Mass Evaluation: aluminium (aluminum) to 26.981 5385(7) from 26.981 5386(8), arsenic to 74.921 595(6) from 74.921 60(2), beryllium to 9.012 1831(5) from 9.012 182(3), caesium (cesium) to 132.905 451 96(6) from 132.905 4519(2), cobalt to 58.933 194(4) from 58.933 195(5), fluorine to 18.998 403 163(6) from 18.998 4032(5), gold to 196.966 569(5) from 196.966 569(4), holmium to 164.930 33(2) from 164.930 32(2), manganese to 54.938 044(3) from 54.938 045(5), niobium to 92.906 37(2) from 92.906 38(2), phosphorus to 30.973 761 998(5) from 30.973 762(2), praseodymium to 140.907 66(2) from 140.907 65(2), scandium to 44.955 908(5) from 44.955 912(6), thulium to 168.934 22(2) from 168.934 21(2), and yttrium to 88.905 84(2) from 88.905 85(2). The Commission also recommends the standard value for the natural terrestrial uranium isotope ratio, N(238U)/N(235U)=137.8(1).

The Commission on Isotopic Abundances and Atomic Weights (ciaaw.org) of the International Union of Pure and Applied Chemistry (iupac.org) has revised the Table of Isotopic Compositions of the Elements (TICE). The update involved a critical evaluation of the recent published literature. The new TICE 2013 includes evaluated data from the "best measurement" of the isotopic abundances in a single sample, along with a set of representative isotopic abundances and uncertainties that accommodate known variations in normal terrestrial materials.

Lead (Pb) isotopic compositions and concentrations, and barium (Ba) and indium (In) concentrations have been analysed at sub-annual resolution in three sections from a < 110 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 ~ 1953 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.

The biennial review of atomic-weight determinations and other cognate data has resulted in changes for the standard atomic weights of five elements. The atomic weight of bromine has changed from 79.904(1) to the interval [79.901, 79.907], germanium from 72.63(1) to 72.630(8), indium from 114.818(3) to 114.818(1), magnesium from 24.3050(6) to the interval [24.304, 24.307], and mercury from 200.59(2) to 200.592(3). For bromine and magnesium, assignment of intervals for the new standard atomic weights reflects the common occurrence of variations in the atomic weights of those elements in normal terrestrial materials.

The aim of this work was to develop thermal ionization mass spectrometry (TIMS) isotopic procedures to measure Zn isotope fractionation (δZn) in natural materials. This work represents the most recent development of Zn isotope measurements and the first δZn identification in terrestrial materials using TIMS and a double spike technique. The developed procedures evaluate and solve several critical analytical issues involved in TIMS Zn isotope analysis. For example, no more than 1μg Zn was used for isotopic analyses which, considering the high ionization potential and low thermal ionization of Zn, represents a useful breakthrough in Zn isotope TIMS analysis. The effect of the ion exchange process on δZn was assessed and found equal to +0.07±0.02‰amu−1 per column. The ionization efficiency of Zn was enhanced to 0.22±0.07%, which is four times more than what was achieved previously. The magnitude of δZn accompanied by the 95% confidence associated uncertainties were calculated relative to the IRMM 3702, using a Monte Carlo approach for each individual analysis, while the calculated average of δZn for number of analysis was accompanied by a 95% confidence calculated using GUM Workbench software. δZn values where always calculated using two different sets of isotopes which always agreed within uncertainty. These developments enabled sub-per mil δZn to be revealed relative to δZn zero for natural materials. Most of the samples measured are Standard Reference Materials SRMs, where, except for BCR-1 and BIR-1, this is the first time Zn isotopic fractionation has been measured in these samples. No previously published results for Zn isotopic fractionation have been published on these samples using double spiking. Consistent δZn of ∼+0.3‰amu−1 was found in 5 sediments from a range of localities. δZn in two metamorphic samples is similar to that found in igneous rocks but different to that found in sedimentary rocks, which is consistent with our understanding that high temperature and pressure processes do not fractionate the composition of chalcophile elements. The isotope fractionation of Zn in a clay sample is within uncertainties the same as the sediments. The isotope fractionation of Zn of −0.088±0.070‰amu−1 was also measured in a standard rice sample. δZn in Antarctic Krill of +0.21±0.11‰amu−1 was found to be similar to the average δZn of +0.281±0.083‰amu−1 for marine sediments. River water was fractionated by −1.09±0.70 ‰amu−1, while restrained tap water yielded the maximum isotope fractionation of −6.39±0.62‰amu−1. δZn in high pure Zn standard materials ranged from −5.11±0.36‰amu−1 for AE 10760 to +0.12±0.16‰amu−1 for Zn IRMM 10440 with some evidence for a relationship between Zn isotope fractionation and its purity. All of the measured isotope fractionation yields an atomic weight within the IUPAC atomic weight of Zn.

The isotope fractionation of Zn in meteorites has been measured for the first time using thermal ionization mass spectrometry and a double spiking technique. The magnitude of delta Zn ranged from -0.29 to +0.38 parts per thousand amu(-1) for five stone meteorites whereas the iron meteorite Canyon Diablo displays delta Zn of 1.11 +/- 0.11 parts per thousand amu(-1). The results for chondrites in this work can be divided into positive and negative delta Zn, supporting a previous proposal that chondrites are a mixture of materials from two different temperature sources. The Zn isotope fractionation present in meteorites may represent a primordial heterogeneity formed in the early solar system. An anomalous isotopic composition of Zn obtained for the Redfields iron meteorite suggests large-scale inherited isotope heterogeneity of the protosolar nebula, or the presence of a parent body that has formed within its own isotopically anomalous reservoir. These anomalies are in the same direction but smaller than nuclear field shift effects observed in chemical exchange reactions. The isotope dilution mass spectrometry (IDMS) technique was used to measure Zn concentration, yielding a range from 20.1 mu g g(-1) to 302 mu g g(-1) in five stone meteorites and from 0.019 to 26 mu g g(-1) in seven iron meteorites. The IDMS-measured abundance of Zn in Orgueil is 302 +/- 14 mu g g(-1) and should be considered for future compilations of the abundance of Zn in the solar system.

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 ∼1757AD to ∼1898AD. ‘Natural’ background Pb concentrations in ∼1757AD average ∼0.2pgg−1 and can be attributed to mineral dust and volcanic emissions, with 206Pb/207Pb ratios reaching up to 1.266±0.002. From ∼1887AD to ∼1898AD, Pb concentrations reached ∼5pgg−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).

A thermal ionisation mass spectrometric technique enabled the abundance of Zn in geological and biological reference materials and water samples to be measured by double spiking isotope dilution mass spectrometry enriched in the 67Zn and 70Zn isotopes. In the past, thermal ionisation mass spectrometry proved to be difficult for low‐level zinc isotopic measurements. The size of Zn samples used for isotopic determination, in particular the biological RMs, represents an important breakthrough. These results represent the most accurate and precise concentrations measured for Zn in these samples. The maximum fractional uncertainty was that for TILL‐3 (2%), while the minimum fractional uncertainty was 0.7% for both BCR‐1 and W‐2. The inhomogeneity of Zn in HISS‐1 was revealed while other reference materials appeared homogeneous at the 95% confidence uncertainty. The certified concentration of Zn in HISS‐1 and IMEP‐19 by their producers are 28% and 3.8% higher than the values measured in this work. These are the first Zn concentration measurements in these materials by the isotope dilution‐TIMS technique, except for BCR‐1, NIES No 9 and IMEP‐19. Reducing the blank enabled accurate measurement in water at the ng g‐1 level demonstrating the applicability of the technique for low‐level Zn samples.

A long known way of anchoring isotope ratio values to the SI system is by means of gravimetrically prepared isotopic mixtures. Thermal ionization mass spectrometry (TIMS) is the traditionally associated measurement technique, but multi-collector double focusing inductively coupled plasma (MC-ICP)-MS now appears to be an attractive alternative. This absolute calibration strategy necessitates that mass discrimination effects remain invariant in time and across the range of isotope ratios measured. It is not the case with MC-ICPMS and the present work illustrates, in the case of Zn isotopic measurements carried out using locally produced synthetic Zn isotope mixtures (IRMM-007 series), how this calibration strategy must be adjusted. First, variation in mass discrimination effects across the measurement sequence is propagated as an uncertainty component. Second, linear proportionality during each individual measurement between normalized mass discrimination and the average mass of the isotope ratios is used to evaluate mass discrimination for the ratios involving low abundance isotopes. Third, linear proportionality between mass discrimination and the logarithm of the isotope ratio values for n(67Zn)/n(64Zn) and n(68Zn)/n(64Zn) in the mixtures is used iteratively to evaluate mass discrimination for the same ratios in the isotopically enriched materials. Fourth, ratios in natural-like materials (including IRMM-3702 and IRMM-651) are calibrated by external bracketing using the isotopic mixtures. The relative expanded uncertainty (k = 2) estimated for n(68Zn)/n(64Zn) and n(67Zn)/n(64Zn) ratio values in the synthetic isotopic mixtures and the natural-like zinc samples was in the range of 0.034 to 0.048%. The uncertainty on the weighing (0.01%, k = 1) was the largest contributor to these budgets. The agreement between these results and those obtained with a single detector TIMS and with another MC-ICPMS further validated this work. The absolute isotope ratio values found for IRMM-3702—material also proposed as “delta 0” for δ-scale isotopic measurements—are n(66Zn)/n(64Zn) = 0.56397 (30), n(67Zn)/n(64Zn) = 0.082166 (35), n(68Zn)/n(64Zn) = 0.37519 (16), and n(70Zn)/n(64Zn) = 0.012418 (23). The derived Zn atomic weight value Ar(Zn) = 65.37777 (22) differs significantly from the current IUPAC value by Chang et al. [1]. Remeasurement, with isotopic mixtures from the IRMM-007 series, of the Zn isotope ratios in the same Chang et al. [1] material have revealed large systematic differences (1.35 (27)% per atomic mass unit) that suggest unrecognized measurement biases in their results.

Eight samples from a planar cross section of one of the natural fission reactor zones at the Oklo U mine were analyzed to determine the abundances and isotopic composition of U, Mo, Ru, Pd, Ag, Cd, Sn, Te and Nd. Fission product concentrations were calculated from the isotopic compositions. The relative abundances of these fission products are different from those produced by fission i.e. portions have been lost or gained from all the samples. The proportions of Te, Ru, 99Ru, Pd and Mo in the eight samples are invariant. We attribute this regularity to retention at the site of production—primary retention. Based upon this interpretation, we suggest that fixed proportions of Ru, Tc, Pd and Mo have been removed from the reactor zone. In contrast, Nd and Sn have been depleted in some regions of the zone and enriched in others. Portions of Ag and virtually all the fissiogenic Cd have been removed from the reactor zone. By analogy with anthropogenic spent fuel, we suggest that the degree of primary retention was controlled by phase assemblages formed in the Oklo natural reactor fuel in response to microscale conditions of pressure, temperature and composition produced by the nuclear reactions. The ability of these putative minerals to retain nuclear products was a function of their stability under physiochemical conditions established by the geological environment over the last 2 Ga. An integrated study of the natural reactors would test our hypothesis and provide valuable information for evaluating the long-term effectiveness of anthropogenic spent fuel as a container of nuclear waste in the geochemical environment.

Seventeen geochemical reference samples have been analysed for Ag, Te, Pd using mass spectrometric isotope dilution analysis. For most samples, analytical data on these elements were lacking. The concentration range encountered was generally in the nanogram levels.