New Analysis Protocol for Stable Isotopes by a Standard Doping Method─An Example of Antimony.

The current analytical methods of stable antimony isotopes are cumbersome and not suitable for rock samples with low antimony content (<1 µg/g). In this study, we propose a new protocol for antimony isotopic analysis with a single column of AG50W-X8 resin and antimony standard doping. This method separates antimony effectively from matrices and then mixes it with the Sb standard. As Te does not affect the accuracy of antimony measurement when the Te/Sb ratio is low, we can obtain an accurate Sb isotope composition of the mixture. Then, we can calculate the antimony isotope composition of natural samples. The error propagation of the mixing and calculation processes was evaluated by the Monte Carlo method, and no significant error was found. The antimony isotope compositions were measured using a Thermo Fisher Scientific Neptune Plus multicollector-inductively coupled-mass spectrometry instrument. The instrumental mass bias of Sb isotopes was corrected with a standard-sample bracketing combined with a Sn internal normalization technique. Using the standard doping method, the measured δ123Sb values of standard solutions (Alfa, SPEX, GSB, and SCP) relative to NIST SRM 3102a were 0.02 ± 0.03‰ (2SD, N = 50), 0.29 ± 0.03‰ (2SD, N = 15), 0.24 ± 0.03‰ (2SD, N = 56), and 0.30 ± 0.03‰ (2SD, N = 15), respectively. The reproducibility for δ123Sb was better than 0.03‰ (2SD) throughout one year. This methodology has been testified by geological samples, yielding δ123Sb identical to the previously reported values. The actual Sb consumption for each sample test is as low as 5 ng. This standard doping method provides new insights into the analytical strategy of stable isotopes.

Hf-Nd-Sr Isotopic Composition of the Tibetan Plateau Dust as a Fingerprint for Regional to Hemispherical Transport.

Large areas of arid regions in the Tibetan Plateau (TP) are undergoing desertification and subsequent aeolian emission and transport. The contribution of TP soils to the atmospheric aerosol burden in Asia and elsewhere is not known. Here, we use Hf, Nd, and Sr isotopes to distinguish the TP from other Asian dust-producing regions and compare the signatures to sediments in major dust sink regions. We found that the Hf-Nd-Sr isotopes of TP soils showed unique spatial signatures. From north to south, 87Sr/86Sr ratios gradually increased, while εNd and εHf values gradually decreased; from west to east, 87Sr/86Sr and εHf gradually increased, while εNd changed indistinctly. The Hf-Nd-Sr isotopic compositions of TP soils were controlled by four geographic isotope regions: the northern, southern, western, and eastern TP. Compared with Asian large deserts, the TP showed a unique isotopic composition, which together exhibited a significant spatial change across Asia. Compared to dust isotopes in prominent sink areas, we found that the TP is an important dust source to eastern TP glaciers, the Chinese Loess Plateau, South China Sea, Japan, and Greenland. This study provides clear isotopic evidence that the TP is a major aeolian contributor in the Northern Hemisphere and may have important implications for the global aeolian cycle.

Direct measurement of Cu and Pb isotopic ratios without column chemistry for bronze materials using MC-ICP-MS.

This study presents a practical method for high-precision Cu and Pb isotope determination without column chemistry for bronze materials using MC-ICP-MS. The standard-sample bracketing method combined with Ga internal normalization (SSBIN) was used to correct the instrumental mass bias during Cu isotopic analysis. The effects of acidity mismatch, concentration mismatch, and matrix effect were rigorously evaluated using a Nu Plasma II MC-ICP-MS in the wet plasma mode. The precision and accuracy of this method were verified by measurements of the Chinese bronze standard material GBW02137 over four months. The δ65Cu of GBW02137 was 0.04 ± 0.02‰ (2s standard deviation, n = 44) relative to NIST SRM 976, which is consistent with the recommended value (0.04 ± 0.02‰). GBW02137 could serve as a potential bracketing standard and quality control sample for in situ Cu isotope measurements of ancient bronze artifacts. The 205Tl/203Tl ratio of 2.3889 and an exponential law were used to correct the instrumental mass discrimination during Pb isotopic analysis. The Pb isotopic ratios determined without column chemistry were within 0.04% of the reference values. Therefore, the method for the direct determination of Cu and Pb isotope presented here is a promising tool for research on bronze materials owing to the chemistry without columns, high precision and accuracy, and rapidity.

Copper Isotope Ratio Measurements of Cu-Dominated Minerals Without Column Chromatography Using MC-ICP-MS.

This study performed a series of comparable experiments (with or without column chromatography) to evaluate whether non-deviated Cu isotope ratios can be obtained directly by Nu Plasma II multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) using standard-sample bracketing with Ga as internal mass bias correction model (C-SSBIN) without column chromatography. Twelve Cu-dominated minerals (copper plate, native copper, chalcopyrite, bornite, chalcocite, digenite, covellite, tetrahedrite, azurite, malachite, atacamite, and cyanotrichite) displayed little drift in δ65Cu values compared with those of minerals with column chromatography, with Δδ65Cuwithout-with ranging from -0.04 to +0.02‰. This means that Cu isotope ratios in Cu-dominated minerals can be achieved without column chromatography, due to the simple matrix and the stability of the machine by using C-SSBIN mode. The acidity and internal standard concentration mismatch effects, as well as the matrix effect, were strictly assessed by Nu Plasma II MC-ICP-MS in a wet-plasma mode in the State Key Laboratory of Continental Dynamics (SKLCD). Finally, a long-term reproducibility of better than ±0.03‰ [n = 38, 2 standard deviations (2s)] were achieved by repeatedly measuring chalcopyrite without column chromatography over 4 months.

Atmospheric deposition and contamination of trace elements in snowpacks of mountain glaciers in the northeastern Tibetan Plateau.

To investigate the large-scale trace element deposition and anthropogenic pollution in mountain glaciers of the northeastern Tibetan Plateau (TP) and its surrounding regions, we analyzed Al and 13 trace elements (As, Cd, Co, Cr, Cs, Cu, Mn, Mo, Ni, Pb, Sb, V, and Zn) in glacier snowpacks collected at the Yuzhufeng, Laohugou No.12, and Qiyi glaciers (YG, LG12, and QG, respectively) in the northeastern TP as well as in the Miaoergou Glacier (MG) in the eastern Tianshan Mountains in June 2017. The concentrations and enrichment factors (EFs) of most trace elements (e.g., As, Cd, Co, Cr, Cu, Ni, and Sb) showed that the largest value appeared in the MG, followed by LG12, and the lowest value appeared in the QG, thereby implying a decreasing influence of anthropogenic emissions on these elements from the west (MG) to the east (QG). The YG inversely exhibited high concentrations but low EFs for As, Cd, Co, Cr, Cs, Cu, Pb, and Sb. Compared to the surrounding regions of the southern and western TP (e.g., NamCo, Mt. Everest, and Pamirs), Japan, and Kathmandu, the trace element concentrations were relatively higher at the YG and MG but relatively lower at the LG12 and QG. The spatial distribution characteristics of trace elements (e.g., Pb and Sb) exhibited a gradually decreasing concentration from west to east in the Tianshan Mountains, and from south to north in the TP, implying two potential transport routes of atmospheric pollutants from Central and South Asia to the northeastern TP. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) backward trajectory model and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations/Cloud-Aerosol Lidar with Orthogonal Polarization (CALIPSO/CALIOP) data reflected that these trace elements in the MG, LG12, and QG predominately originated from the western and surrounding areas, whereas in the YG they were mainly derived from a local source and South Asia through long-distance transport.

[High-precision in situ analysis of the lead isotopic composition in copper using femtosecond laser ablation MC-ICP-MS and the application in ancient coins].

In the present study we set up a femtosecond laser ablation MC-ICP-MS method for lead isotopic analysis. Pb isotopic composition of fifteen copper (brass, bronze) standard samples from the National Institute of Standards Material were analyzed using the solution method (MC-ICP-MS) and laser method (fLA-MC-ICPMS) respectively, the results showed that the Pb isotopic composition in CuPb12 (GBW02137) is very homogeneous, and can be used as external reference material for Pb isotopic in situ analysis. On CuPb12 112 fLA-MC-ICPMS Pb isotope analysis, the weighted average values of the Pb isotopic ratio are in good agreement with the results analyzed by bulk solution method within 2sigma error, the internal precision RSEs of the 208 Pb/204 Pb ratio and 207 Pb/206 Pb ratio are less than 90 and 40 ppm respectively, and the external precision RSDs of them are less than 60 and 30 ppm respectively. Pb isotope of thirteen ancient bronze coins was analyzed via fLA-MC-ICPMS, the results showed that the Pb isotopic composition of ancient coins of different dynasties is significantly different, and not all the Pb isotopic compositions in the coins even from the same dynasty are in agreement with each other.