Determination Of Pb Isotope Ratios Research Articles

Simultaneous In Situ Determination of Pb Isotope Ratios and Trace Element Concentrations in Melt Inclusions by LASS‐ICP‐MS

AbstractMelt inclusions provide unique insights into magmatic sources and processes. This study presents a method for simultaneously measuring Pb isotopes and trace elements in melt inclusions using a 193 nm excimer laser ablation system coupled to a multiple‐collector inductively coupled plasma‐mass spectrometer (MC‐ICP‐MS) and a sector‐field ICP‐MS (SF‐ICP‐MS). The ablated aerosol was split with a Y‐shaped connector into two gas streams, which were simultaneously transported into two mass spectrometers. Lead isotopes were measured on the MC‐ICP‐MS, while trace element concentrations were determined on the SF‐ICP‐MS. Little analytical bias was observed when the aerosol is divided into variable proportions (5:5, 6:4, 7:3, 8:2–9:1) to the two instruments. The precision and accuracy of this method were evaluated by analyzing five geological reference glasses with two laser spot diameters (33, and 45 μm). All the 33 measured trace element concentrations are consistent with the reference values (±10%) and have precisions less than 15% (2RSD). The precisions of the 208Pb/206Pb, and 207Pb/206Pb ratios correlate with Pb concentrations. From BHVO‐2G (Pb = 1.6 ppm) to TB‐1G (Pb = 16.1 ppm), the precision on these ratios improve from about 0.4%–0.2% with a 33 μm laser spot diameter. The mean Pb isotope ratios for the five reference glasses are within 0.15% of the reference values. Using our new method, Pb isotope ratios and trace element contents of plagioclase‐hosted melt inclusions in a mid‐ocean ridge basalt from the Indian Ocean were measured.

Direct determination of Pb isotope ratios in archaeological materials by coupling liquid chromatography to multicollector ICP-MS

On-line coupling of HPLC-MC-ICP-MS allows Pb isotope ratio measurements in archaeological samples without prior off-line Pb separation.

Lead concentrations and stable lead isotope ratios in moss in Slovenia and Switzerland

Using moss as a biomonitor is an established technique for monitoring atmospheric deposition of trace elements, including lead (Pb), a metal that is toxic for most organisms. Lead enters the environment during production and combustion processes and during the use of leaded gasoline. There are four stable isotopes of Pb, and the isotopic composition can be used to determine sources and pathways of atmospheric Pb pollution.In this study we determined Pb concentrations and isotope ratios in moss (Hypnum cupressiforme and Pleurozium schreberi) collected from 1990 to 2015 in Switzerland and from 2006 to 2015 in Slovenia. We used microwave sample digestion and inductively coupled plasma mass spectrometry (ICP-MS) for Pb concentrations and multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) for Pb isotope ratio determination. The aim was to assess the change in atmospheric Pb deposition over time and the differences between and within the two countries. Additionally, we assessed the current Pb isotope ratios for both countries and evaluated the change over time in Switzerland.The Pb concentration in moss decreased significantly over time in both countries. In 2015, at the end of the study period, concentrations were significantly higher in Slovenia compared to in Switzerland. Higher Pb concentrations in Slovenia may be related to the prolonged use of leaded gasoline or to the larger influence of industrial sources. Within Switzerland Pb concentrations differed significantly between regions. These differences are likely a consequence of different population densities and precipitation amounts. In Slovenia there were no significant differences between the regions, indicating that there are no large differences in Pb emissions.The 206Pb/207Pb and 208Pb/206Pb isotope ratios differed between Slovenia and Switzerland and between some regions within Switzerland. This finding shows that Slovenia and Switzerland, as well as the different regions within Switzerland, are influenced by different Pb sources. In Switzerland, 206Pb/207Pb increased and 208Pb/206Pb decreased over time and shifted away from the isotopic signature of leaded gasoline. Additionally, both isotope ratios became more homogeneous within Switzerland, which suggests that the sources of Pb became more similar. Overall, the Pb isotope ratios reflect the diminishing influence of leaded gasoline and indicate an increasing importance of industry, coal burning and natural bedrock as Pb sources.

Marine sponges as a powerful tool for trace elements biomonitoring studies in coastal environment

In this work, we performed a comparative study on six marine sponge species collected along the French Mediterranean and Irish coasts for their TEs accumulation. Intra and inter-species variabilities were examined. Among the Mediterranean species, Cymbaxinella damicornis accumulates significantly more As and Cu than others sponge species; Chondrilla nucula more Ni and Mo and Acanthella acuta more Ag. Among Irish samples, Hymeniacidon perlevis showed higher accumulation properties for most of TEs in comparison to Halichondria panicea. Bioconcentration Factors were > 1 in all species for most of TEs. This study suggests that TEs bioaccumulation is most likely associated to differences in morphological features and/or to specific bacterial communities associated to different species. The determination of Pb isotope ratios revealed mainly natural Pb sources for Mediterranean and Kilkieran Bay's samples, and rather anthropogenic influence for Belfast samples. This study confirms that sponges represent a powerful tool for biomonitoring studies.

Baseline study on trace and rare earth elements in marine sediments collected along the Namibian coast

Namibia is a fast-growing country with extensive mineral extraction activities used in diamond, fluorspar, uranium, and metals production. To assess the impact of land based human activities on the Namibian coastal marine environment, 25 elements were analyzed in 22 surface sediments samples collected along the coast. After applying a variety of pollution assessment indices (Enrichment Factor, Igeo and Pollution Load Indexes) was concluded that As, Cd and Sb were considerably enriched in the sediments from several sites, while Cu, Pb and Zn showed very high enrichment near the Walvis Bay harbor. Pearson's correlation and Principal Component Analysis were used to investigate common metal sources. Additionally, the determination of Pb isotope ratios confirmed the contribution of land based human activities at Walvis Bay and Lüderitz as sources of pollution. The analysis of REEs did not reveal any important enrichment due to anthropogenic activities, but provides a needed baseline for further investigations.

Development of procedure for measurement of Pb isotope ratios in seawater by application of seaFAST sample pre-treatment system and Sector Field Inductively Coupled Plasma Mass Spectrometry

Anthropogenic Pb in the oceans, derived from high-temperature industrial processes, fuel combustion and incineration can have an isotopic signature distinct from naturally occurring Pb, supplied by rock weathering. To identify the different pollution sources accurately and to quantify their relative contributions, Pb isotope ratios are widely used.Due to the high salt content (approximately 3.5% of total dissolved solids) and very low levels of Pb (typically from 1 to 100ngL−1) in seawater the determination of Pb isotope ratios requires preliminary matrix separation and analyte preconcentration. An analytical protocol for the measurements of Pb isotope ratios in seawater combining seaFAST sample pre-treatment system and Sector Field Inductively Coupled Plasma Mass Spectrometry (SF ICP-MS) was developed. The application of seaFAST system was advantageous, because of its completely closed working cycle and small volumes of chemicals introduced in pre-treatment step, resulting in very low detection limits and procedural blanks.The preconcentration/matrix separation step was also of crucial importance for minimizing the isobaric and matrix interferences, coming from the seawater. In order to differentiate between anthropogenic and natural Pb sources, particular attention was paid to the determination of 204Pb isotope because of its implication in some geological interpretations.The validation of the analytical procedure was effectuated according to the recommendations of the ISO/IEC 17025 standard. The method was validated by processing the common Pb isotope reference material NIST SRM 981. All major sources of uncertainty were identified and propagated together following the ISO/GUM guidelines. The estimation of the total uncertainty associated to each measurement result was fundamental tool for sorting the main sources of possible biases. The developed analytical procedure was applied to the coastal and open seawater samples, collected in different regions of the world and revealed that the procedure is applicable for the measurement of Pb isotope ratios in seawater with combined uncertainty adequate to discuss the origin of Pb pollution in the ocean.

Lead isotopes and elemental composition of Roman fistulae plumbeae aquariae from Conimbriga (Portugal) using Quadrupole ICP-MS

Lead metal and lead artefacts were widespread over the Roman world, as consequence of its large use in public buildings, namely as plumbing on hydraulic systems of Roman cities and villae. The determination of Pb isotope ratios combined with minor and trace element contents of such lead artefacts may constitute a powerful tool for provenance studies as well as in the assessment of trade routes during the Roman period. In the present work forty four fistulae plumbeae from the hydraulic systems installed at Conimbriga were analysed using a quadrupole based ICP-MS. The overall results demonstrate the suitableness of this well-established and economic analytical technique involving simple sample preparation and high throughput. Pb isotopic patterns present high scattered distributions which suggest different provenances of the raw material. Ag, As, Bi, Cu, Ni, Sb, and Sn contents were determined in an attempt to identify the type of raw materials and the metallurgical process used to obtain the lead metal. Sn content points to the frequent use of recycled lead. The Pb isotope ratios of samples of lead pipes made with metal probably not recycled indicate the use of raw materials (galena ores) from Sierra Morena mines or desilvered litharge resulting from silver cupellation probably using argentiferous jarosite ores from the Iberian Pyrite Belt (Rio Tinto mines).

High-precision in situ analysis of Pb isotopes in glasses using 1013 Ω resistor high gain amplifiers with ultraviolet femtosecond laser ablation multiple Faraday collector inductively coupled plasma mass spectrometry

The use of 1013 Ω amplifiers enabled high precision Pb isotope analysis in situ using UV femtosecond MFC-ICPMS.

Effects of simple acid leaching of crushed and powdered geological materials on high‐precision Pb isotope analyses

AbstractWe present new results of simple acid leaching experiments on the Pb isotope composition of USGS standard reference material powders and on ocean island basalt whole rock splits and powders. Rock samples were leached with cold 6 N HCl in an ultrasonic bath, then on a hot plate, and washed with ultrapure H2O before sample digestion in HF‐HNO3 and chromatographic purification of Pb. Lead isotope analyses were measured by Tl‐doped MC‐ICPMS. Intrasession and intersession analytical reproducibilities of repeated analyses of both synthetic Pb solutions and Pb from single digests of chemically processed natural samples were generally better than 100 ppm (2 SD). The comparison of leached and unleached samples shows that leaching consistently removes variable amounts of contaminants that differ in Pb isotopic composition for different starting materials. For repeated digests of a single sample, analyses of leached samples reproduce better than those of unleached ones, confirming that leaching effectively removes most of the heterogeneously distributed extraneous Pb. Nevertheless, the external reproducibility of leached samples is still up to an order of magnitude worse than that of Pb solution standards (∼100 ppm). More complex leaching methods employed by earlier studies yield Pb isotope ratios within error of those produced by our method and at similar levels of reproducibility, demonstrating that our simple leaching method is as effective as more complex leaching techniques. Therefore, any Pb isotope heterogeneity among multiple leached digests of samples in excess of the external reproducibility is attributed to inherent isotopic heterogeneity of the sample. The external precision of ∼100 ppm (2 SD) achieved for Pb isotope ratio determination by Tl‐doped MC‐ICPMS is thus sufficient for most rocks. The full advantage of the most precise Pb isotope analytical methods is only realized in cases where the natural isotopic heterogeneity among samples in a studied suite is substantially below 100 ppm.

Classification of the geographic origin of cigarettes according to Pb isotope ratios by inductively coupled plasma dynamic reaction cell mass spectrometry

ICP-DRC-MS was developed for the determination of Pb isotope ratios to distinguish between the geographic origins of cigarettes.

Precise Pb isotope ratio determination of picogram-size samples: A comparison between multiple Faraday collectors equipped with 1012 Ω amplifiers and multiple ion counters

While typical ion-counting peak hopping methods using a single Daly detector or a single secondary electron multiplier have proven very effective in analyzing small Pb samples by TIMS, the measurements often require long acquisition times, typically of several hours. Here we compare and evaluate static multi-collector determination of Pb isotope ratios in samples containing between 100 and 1pg total Pb using Faraday detectors, equipped with 1012Ω feedback resistors in the current amplifier system, versus a multiple ion counting (MIC) system, installed in a Triton Plus TIMS. Faraday cup measurements of pg size Pb samples using 1012Ω amplifiers require precise measurement of long baselines for optimal repeatability (defined as internal precision or the precision of a single run) and intermediate precision (defined as the closeness of the replicated measurements over an extended period of time). In our system, using a 20min baseline before and after the measurement, we achieved a repeatability of 0.02–0.03% (2SE) and an intermediate precision of 0.05% (2SD) on 207Pb/206Pb and 208Pb/206Pb in as little as 1h for samples containing between 80 and 10pg Pb. This is equivalent to the performance obtained from a 4 to 5hour-long single SEM peak hopping analysis of larger (10.0–0.5ng) samples. For measurements in MIC mode, the main analytical uncertainty is the relative instability of the detector yields, which is 0.1–0.3% (2SD; following a 1hour detector stabilization period). Using a correction based on the average yield measured before and after sample analysis, we achieved a repeatability of 0.03%–0.06% (2SE) and an intermediate precision of 0.18%–0.23% (2SD) on 207Pb/206Pb for 80 to 10pg loads. For sample sizes between 10 and 1pg, which were only measured in MIC mode because the 204Pb intensity is below detection limit in Faraday mode, the main source of uncertainty is the variable loading blank contribution (5–15%). We conclude that a Faraday array equipped with 1012Ω amplifiers performs very well for Pb sample load sizes down to 10pg, allowing much more rapid data acquisition than peak-hoping SEM measurements and producing data that is 4–5 times more precise than static MIC measurements. In contrast, the MIC system offers considerable promise for tracer Pb work in the sub-10pg Pb analyte range where data with a few % level of accuracy and precision are useful, providing that acceptable total procedural blanks (below 0.1pg) can be achieved.

Final report of the key comparison CCQM-K98: Pb isotope amount ratios in bronze

Isotope amount ratios are proving useful in an ever increasing array of applications that range from studies unravelling transport processes, to pinpointing the provenance of specific samples as well as trace element quantification by using isotope dilution mass spectrometry (IDMS). These expanding applications encompass fields as diverse as archaeology, food chemistry, forensic science, geochemistry, medicine and metrology. However, to be effective tools, the isotope ratio data must be reliable and traceable to enable the comparability of measurement results.The importance of traceability and comparability in isotope ratio analysis has already been recognized by the Inorganic Analysis Working Group (IAWG) within the CCQM. While the requirements for isotope ratio accuracy and precision in the case of IDMS are generally quite modest, 'absolute' Pb isotope ratio measurements for geochemical applications as well as forensic provenance studies require Pb isotope ratio measurements of the highest quality. To support present and future CMCs on isotope ratio determinations, a key comparison was urgently needed and therefore initiated at the IAWG meeting in Paris in April 2011. The analytical task within such a comparison was decided to be the measurement of Pb isotope amount ratios in water and bronze.Measuring Pb isotope amount ratios in an aqueous Pb solution tested the ability of analysts to correct for any instrumental effects on the measured ratios, while the measurement of Pb isotope amount ratios in a metal matrix sample provided a real world test of the whole chemical and instrumental procedure. A suitable bronze material with a Pb mass fraction between 10 and 100 mg•kg-1 and a high purity solution of Pb with a mass fraction of approximately 100 mg•kg-1 was available at the pilot laboratory (BAM), both offering a natural-like Pb isotopic composition.The mandatory measurands, the isotope amount ratios n(206Pb)/n(204Pb), n(207Pb)/n(204Pb) and n(208Pb)/n(204Pb) were selected such that they correspond with those commonly reported in Pb isotopic studies and fully describe the isotopic composition of Pb in the sample. Additionally, the isotope amount ratio n(208Pb)/n(206Pb) was added, as this isotope ratio is typically measured when performing Pb quantitation by IDMS involving a 206Pb spike.Each participant was free to use any method they deemed suitable for measuring the individual isotope ratios. However, the majority of the results were obtained by using muIti-collector ICPMS or TIMS. The key requirements for all analytical procedures were a traceability statement for all results and the establishment of an uncertainty budget meeting a target uncertainty for all ratios of 0.2 %, relative (k=1). Additionally, the use of a Pb-matrix separation procedure was encouraged.The obtained overall result was excellent, demonstrating that the individual results reported by the NMIs/DIs were comparable and compatible for the determination of Pb isotope ratios. MC-ICPMS and MC-TIMS data were consistent with each other and agree to within 0.05 %. The corresponding uncertainties can be considered as realistic uncertainties and mainly range from 0.02 % to 0.08 % (k=1).As stated above isotope ratios are being increasingly used in different fields. Despite the availability and ease of use of new mass spectrometers, the metrology of unbiased isotope ratio measurements remains very challenging. Therefore, further comparisons are urgently needed, and should be designed to also engage scientists outside the NMI/DI community. Possible follow-up studies should focus on isotope ratio and delta measurements important for environmental and technical applications (e.g. B), food traceability and forensics (e.g. H, C, N, O, S and 87Sr/86Sr) or climate change issues (e.g. Li, B, Mg, Ca, Si).Main text.To reach the main text of this paper, click on Final Report.The final report has been peer-reviewed and approved for publication by the CCQM.

Lichen monitoring as a potential tool in environmental forensics: case study of the Cu smelter and former mining town of Karabash, Russia

Abstract The aim of this paper is to showcase the use of lichens in environmental forensics from an assessment of atmospheric deposition in and around the Cu smelter and former mining town of Karabash, Ural Mountains of Russia. Hypogymnia physodes was collected on its bark substrate in July 2001 from a ‘reference’ site ( c. 25 km SW of Karabash) and transplanted to 10 stations along an approximately 60 km SSW–NNE transect centred on Karabash. Transplants were collected after 2 and 3 month exposure periods. The elemental compositions of Hypogymnia and potential sources of particulates in the study area (smelter blast furnace and converter dusts, wastes, tailings, road dusts, metallurgical slags and top soils) were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) and quadrupole ICP mass spectrometry (ICP-MS), and the Pb isotope compositions of the lichens and smelter dusts by multicollector ICP-MS. Particulates on lichen surfaces were analysed by scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). The method of lichen transplantation, combined with multi-element and surface particle elemental analysis, high-precision Pb isotope ratio determinations and modelling, was shown to be useful for the tracing of the smelter signal, and components from different smelter processes, for more than 25 km from Karabash town. The lichen monitoring methodology is discrete and comparatively low cost, enabling atmospheric deposition from natural and anthropogenic sources to be determined over short (<3 month) periods, and is therefore a valuable qualitative tool for environmental forensics.

Fast and Precise Method for Pb Isotope Ratio Determination in Complex Matrices using GC-MC-ICPMS: Application to Crude Oil, Kerogen, and Asphaltene Samples

A new method to determine Pb isotope ratio without ion-exchange-matrix separation is proposed. After acid digestion, Pb was ethylated to Et(4)Pb, separated from the digested solution (black shale, asphaltene, crude oil and kerogen) by extraction in isooctane, and then injected into a gas chromatograph coupled to a multicollector inductively coupled plasma mass spectrometer. Seven isotopes ((202)Hg, (203)Tl, (204)Pb, (205)Tl, (206)Pb, (207)Pb, (208)Pb) were monitored simultaneously with peak duration of 23 s. GC elution was operated under wet plasma conditions where a thallium standard solution was introduced to the mass spectrometer for mass bias correction. The total time of the procedure (sample preparation and analysis, after acid digestion) was reduced by a factor of 15 compared to conventional-continuous sample introduction. Data treatment was carried out using the linear regression slope method. Mass bias was corrected using the double correction method (first thallium normalization followed by classical bracketing). For the (208/206)Pb and (207/206)Pb ratios, precision (2RSD(EXT), n = 21) was 49 and 69 ppm, and the bias between experimental results and reference values was better than 0.0033 and 0.0007 ‰, when injecting 1.2 ng of ethylated Pb SRM NIST 981 solution. Results obtained by this method were validated by comparison with those obtained via conventional-continuous sample introduction. The applicability of this approach was demonstrated with the analysis of black shale, asphaltene, crude oil and kerogen samples.

ICP-MS determination of lead isotope ratios in legal and counterfeit cigarette tobacco samples

A method for the determination of Pb isotope ratios (IR) in cigarette tobacco by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) has been developed and applied to tobacco samples from genuine and counterfeit cigarettes obtained in the USA. The IR 207Pb/206Pb, 208Pb/206Pb, 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb were measured using a Q-ICP-MS instrument. Two certified reference materials, grown in the USA and Bulgaria, were also analysed for comparison with the tobacco samples, as were tobacco samples from cigarettes obtained in Pakistan and China. The precision of the results was sufficient to distinguish between the counterfeit and genuine USA cigarettes. All of the genuine cigarettes and both reference materials, grown in different regions, were statistically distinct based on the measured ratios. The counterfeit cigarettes were indistinguishable from the reference material grown in Bulgaria. The technique shows promise as a method for identifying counterfeit cigarettes, possibly determining the source region.

From volcanic rock powder to Sr and Pb isotope ratios: a fit-for-purpose procedure for multi-collector ICP–mass spectrometric analysis

Geochemical research into volcanic rocks often involves isotopic analysis of whole rock powders. The method of Deniel and Pin (Anal. Chim. Acta, 2001, 426, 95–103) for simultaneous isolation of strontium and lead using extraction chromatography via Sr spec™ resin was therefore adapted into a straightforward procedure for Sr and Pb isotope ratio determination by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The main focus was to reduce their rather extensive and costly cleaning procedures for resin and columns without negatively affecting data quality. It was furthermore demonstrated that non-quantitative Sr and Pb recoveries do not compromise the quality of the isotope data obtained and that no Pb isotopic fractionation occurs on the Sr spec™ resin. The accuracy of the analyses was assessed by monitoring rock reference materials. GSJ basalt JB-2, commonly regarded as the most homogeneous Pb isotopic rock reference material, hereby produced one anomalous Pb isotopic composition out of eight analyses, suggesting that JB-2 might also be affected by nugget contamination.

Measuring 0.01‰ to 0.1‰ isotopic variations by MC-ICPMS—testing limits for the first time with Pb δ-iCRMs

A blind comparison on Pb-isotope δ-scale measurements by MC-ICPMS of 0.01‰ to 0.1‰ level was organised, involving five laboratories. Test samples were obtained from the series of candidate ERM-3810 δ-isotopic Certified Reference Materials (δ-iCRMs), and comprise four pairs of a material with ∼natural Pb-isotopic composition (‘delta zero’ or ‘δ-0’) and the same natural Pb progressively enriched in 207Pb (with δ207Pb values certified to ∼0.1% relative uncertainty, k = 2). Participants were free to apply the measurement strategy of their choice. A result was considered ‘acceptable’ only when, simultaneously, there was agreement within stated uncertainties with the corresponding reference value and the relative uncertainty stated by the participant was < 100%. This study illustrates the high degree of difficulty inherent to these δ-scale measurements by ‘routine’ MC-ICPMS methodologies (in this case, three participants reported 55% of their results which were deemed accurate, and the other two reported none). The closer to unity the isotope ratio value the better the results became (‘acceptable’ results mostly for δ7/6‰ and δ7/8‰ measurements). This first experiment of its kind demonstrates that Pb δ-scale isotopic measurements by MC-ICPMS can be reliably carried out down to 0.05‰ levels (two participants delivered accurate results above this threshold systematically for δ7/6‰, δ7/8‰ and δ7/4‰). Below this limit, at ∼0.01‰ and ∼ 0.03‰ levels, results are no longer consistent or reproducible and appear to be susceptible to a number of effects introducing error (such as short term changes in mass discrimination) which are either not well understood, or not controlled and/or not corrected for at a sufficiently low level of uncertainty. These results also suggest that ‘routine’ methods for absolute (calibrated) Pb-isotope ratio determination by MC-ICPMS produce relative combined uncertainties on results which are unlikely to be better than 0.05‰ (k = 2).

Precise determination of Pb isotope ratios by simple double spike MC-ICP-MS technique without Tl addition

A double-spike multicollector ICP-MS (DS-MC-ICP-MS) technique for Pb isotope analysis without Tl addition is established and its analytical performance is examined in detail. This simple DS-MC-ICP-MS technique using 20 ng ml−1 gave averages of 16.9417, 15.4988 and 36.7196 with reproducibilities of 0.007, 0.008 and 0.009% (RSD, n = 35), respectively, for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb in NIST 981 solution, corresponding to consumption of 4 ng of Pb in a pair of spiked and non-spiked measurements. The average is consistent with those obtained by previous studies by DS-TIMS and DS-MC-ICP-MS with Tl addition. The reproducibility (RSD %) of 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb improves from 0.26, 0.54 and 0.69% to 0.0022, 0.0030 and 0.0029% as the Pb consumption during analysis increases from 20 pg to 11 ng. The reproducibility with 11 ng is similar to or even better than those by DS-TIMS, MC-ICP-MS with Tl addition, or with DS-Tl addition. The accuracy of the simple DS-MC-ICP-MS technique for Pb, including the column chemistry, is further confirmed by analysis of actual silicate sample, JB-3.

Space charge and mass discrimination effects on lead isotope ratio measurements by ICP-QMS in environmental samples with high uranium content

The accuracy of Pb isotope ratio determinations by ICP-QMS in the presence of different U concentrations was investigated. The influence of U was very severe due to space charge and mass discrimination effects, which play an important role in the process of Pb signal acquisition. In this work, solutions of the isotope reference material NBS 981, spiked with different amounts of U, were analysed for Pb isotope ratios using an ICP-QMS and a MC-ICP-MS. The results obtained demonstrate the existence of a strong interference of U content in the analytical process, the same behaviour being exhibited by both pieces of equipment. In order to optimize an analytical procedure to perform Pb isotopic ratio determinations with an ICP-QMS, a method with external standardization and matrix match was developed. This method provided results in excellent agreement with those obtained by thermal ionization mass spectrometry (r2 = 0.9999). The developed methodology was shown to have suitable analytical quality for Pb isotope measurements when they are used for identification of different Pb sources in environmental studies and applications.

Lead Isotopes in Lichen Transplants around a Cu Smelter in Russia Determined by MC-ICP-MS Reveal Transient Records of Multiple Sources

Transplants of the lichen Hypogymnia physodes, which is relatively tolerant to SO2 and heavy metals, were deployed for 3 months over a 60 km long SW-NE transect centered on a highly polluting Cu smelter and its adjoining town of Karabash, southern Urals, Russia. The abundance of 206Pb, 207Pb, 208Pb, and 204Pb were determined by MC-ICP-MS. The measurement of 204Pb revealed critical features, which would otherwise remain concealed: (i) The precise isotope ratios referenced to 204Pb allowed several different sources to be resolved even within the small area covered: (a) the obvious pollutant source of the Karabash Cu smelter; (b) two dispersed sources, likely to include soil with lower and different contributions of thorogenic and uranogenic lead; and (c) one anthropogenic source with higher contribution of 235U derived Pb. (ii) In part of the transect, the Pb isotope composition changed while the Pb concentrations remained the same. This indicates that the Pb content of the transplantation material from the background site was largely replaced and that the transplants provide a transient record reflecting a continuous accumulation and loss of environmental Pb, probably mainly in the form of extracellular particles. Overall, the method of lichen transplantation coupled with Pb isotope ratio determinations proved effective in assessing the usefulness of lichens in biomonitoring and in resolving different sources of atmospheric deposition.