Precise isotope-ratio measurements of lead species by capillary gas chromatography hyphenated to hexapole Multicollector ICP–MS

The precision and accuracy of lead isotope-ratio determination on a short transient signal has been assessed by coupling capillary gas chromatography to the Isoprobe (Micromass, UK), a single-focusing inductively coupled plasma mass spectrometer with multicollector detection. A T-piece connecting the GC transfer line to the torch enabled continuous aspiration of thallium solution for mass-bias correction. The volatile lead species PbEt₄ was derivatized from NIST isotopic certified lead standard SRM 981 and different amounts of PbEt₄ dissolved in iso-octane were injected into the GC. Chromatograms were recorded in multicollection mode by use of Faraday cups; seven isotopes (²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb, ²⁰⁸Pb, ²⁰³Tl, ²⁰⁵Tl, and ²⁰²Hg) were monitored simultaneously at a transient resolution of 160 ms. PbEt₄ peaks were obtained with a half-width of 1.2 s and a base width of 3.5 s. Lead isotope ratios were calculated from the peak areas integrated for each lead isotope, giving precision in the range of 0.02 to 0.07% for ratios of high-abundant isotopes and injections of 5 and 50 pg absolute amount as lead (five replicates). Mass bias was found to be about 0.5% per mass unit and was corrected by using the continuously measured thallium signals at ²⁰³Tl and ²⁰⁵Tl. After mass-bias correction, deviation of the certified lead ratio values was found to be in the range of 0.02 to 0.15% accuracy.     

Isotope-ratio measurements of lead in NIST standard reference materials by multiple-collector inductively coupled plasma mass spectrometry

The capability of a second-generation Nu Instruments multiple collector inductively coupled plasma mass spectrometer (MC-ICP-MS) has been evaluated for precise and accurate isotope-ratio determinations of lead. Essentially the mass spectrometer is a double-focusing instrument of Nier-Johnson analyzer geometry equipped with a newly designed variable-dispersion ion optical device, enabling the measured ion beams to be focused into a fixed array of Faraday collectors and an ion-counting assembly. NIST SRM Pb 981, 982, and 983 isotopic standards were used. Addition of thallium to the lead standards and subsequent simultaneous measurement of the thallium and lead isotopes enabled correction for mass discrimination, by use of the exponential correction law and 205Tl/203Tl = 2.3875. Six measurements of SRM Pb-982 furnished the results 206Pb/204Pb = 36.7326(68), 207Pb/204Pb = 17.1543(30), 208Pb/204Pb = 36.7249(69), 207Pb/206Pb = 0.46700(1), and 208Pb/206Pb = 0.99979(2); the NIST-certified values were 36.738(37), 17.159(25), 36.744(50), 0.46707(20), and 1.00016(36), respectively. Direct isotope lead analysis in silicates can be performed without any chemical separation. NIST SRM 610 glass was dissolved and introduced into the MC-ICP-MS by means of a micro concentric nebulizer. The ratios observed were in excellent agreement with previously reported data obtained by TIMS and laser ablation MC-ICP-MS, despite the high Ca/Pb concentration ratio (200/1) and the presence of many other elements at levels comparable with that of lead. Approximately 0.2 microg lead are sufficient for isotope analysis with ratio uncertainties between 240 and 530 ppm.     

Accuracy and long-term reproducibility of lead isotopic measurements by multiple-collector inductively coupled plasma mass spectrometry using an external method for correction of mass discrimination

The precision of isotopic measurements of Pb by thermal ionization mass spectrometry (TIMS) is limited by the fact that this element does not possess an invariant isotope ratio that can be used for the correction of mass fractionation by internal normalization. Multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS) can overcome this limitation, because with plasma ionization, elements with overlapping mass ranges are thought to display identical mass discrimination. With respect to Pb, this can be exploited by the addition of Tl to the sample solutions; the mass discrimination factor obtained for Tl can then be used for the correction of the measured Pb isotope ratios. In this article we present the results of a detailed study that investigates the accuracy and precision of such an external correction technique for mass discrimination based upon the results of multiple analyses of a mixed standard solution of NIST SRM-981 Pb and SRM-997 Tl. Our data indicate that normalization of the Pb isotope ratios to the certified isotopic composition of SRM-997 Tl produces Pb isotopic results that are significantly lower than recently published reference values by TIMS. This systematic offset can be eliminated by renormalization of the Pb data to a different Tl isotopic composition to obtain an empirically determined mass discrimination factor for Pb that generates accurate results. It is furthermore shown that a linear law is least suited for the correction of mass discrimination, whereas a power or exponential law function provide significantly more accurate and precise results. In detail, it appears that a power law may provide the most appropriate correction procedure, because the corrected Pb isotope ratios display less residual correlations with mass discrimination compared to the exponentially corrected data. Using an exponential or power law correction our results, obtained over a period of over seven months, display a precision (2σ) of better than 60 parts per million (ppm) for ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁷Pb/²⁰⁶Pb and of better than 350 ppm for ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb. This represents a significant improvement compared to conventional TIMS techniques and demonstrates the potential of MC-ICPMS for routine, high-precision measurements of Pb isotopic compositions.     

电感耦合等离子体质谱法测定黄沙土壤中铅同位素比

用电感耦合等离子体质谱法（ＩＣＰ—ＭＳ）测定了５个黄沙原土样品中铅同位素比２０７Ｐｂ／２０６Ｐｂ、２０８Ｐｂ／２０６Ｐｂ，样品来自被认为是黄沙气溶胶源地区，为了使铅同位素测量中质量偏差和漂移减至最少，在样品中加入了铊标准溶液，测量２０５Ｔｌ／２０３Ｔｌ比，校正质量数差别选择的影响．同时，采用ＩＣＰ—ＭＳ和电感耦合等离子体原子发射光谱法（ＩＣＰ一ＡｌＳ）测定了随粒径变化样品中１２种元素浓度的变化．     

High-precision measurements of seawater Pb isotope compositions by double spike thermal ionization mass spectrometry

A new method for the determination of seawater Pb isotope compositions and concentrations was developed, which combines and optimizes previously published protocols for the separation and isotopic analysis of this element. For isotopic analysis, the procedure involves initial separation of Pb from 1 to 2 L of seawater by co-precipitation with Mg hydroxide and further purification by a two stage anion exchange procedure. The Pb isotope measurements are subsequently carried out by thermal ionization mass spectrometry using a ²⁰⁷Pb–²⁰⁴Pb double spike for correction of instrumental mass fractionation. These methods are associated with a total procedural Pb blank of 28 ± 21 pg (1sd) and typical Pb recoveries of 40–60%. The Pb concentrations are determined by isotope dilution (ID) on 50 mL of seawater, using a simplified version of above methods. Analyses of multiple aliquots of six seawater samples yield a reproducibility of about ±1 to ±10% (1sd) for Pb concentrations of between 7 and 50 pmol/kg, where precision was primarily limited by the uncertainty of the blank correction (12 ± 4 pg; 1sd). For the Pb isotope analyses, typical reproducibilities (±2sd) of 700–1500 ppm and 1000–2000 ppm were achieved for ²⁰⁷Pb/²⁰⁶Pb, ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, ²⁰⁸Pb/²⁰⁴Pb, respectively. These results are superior to literature data that were obtained using plasma source mass spectrometry and they are at least a factor of five more precise for ratios involving the minor ²⁰⁴Pb isotope. Both Pb concentration and isotope data, furthermore, show good agreement with published results for two seawater intercomparison samples of the GEOTRACES program. Finally, the new methods were applied to a seawater depth profile from the eastern South Atlantic. Both Pb contents and isotope compositions display a smooth evolution with depth, and no obvious outliers. Compared to previous Pb isotope data for seawater, the ²⁰⁶Pb/²⁰⁴Pb ratios are well correlated with ²⁰⁷Pb/²⁰⁶Pb, underlining the significant improvement achieved in the measurement of the minor ²⁰⁴Pb isotope.     

Determination of sources of lead in tap water by inductively coupled plasma mass spectrometry (ICP-MS)

We measured the concentrations of Pb and its isotope ratios in coconmittantly obtained tap water and plumbing materials by inductively coupled mass spectrometry (ICP-MS). The Pb concentrations were determined by external calibration with²⁰⁹Bi as an internal standard. Isotope ratios were measured and mass discrimination corrected by normalization to NIST SRM-981 (common lead isotopic standard). Student/s t-test was used to compare the isotopic ratios of²⁰⁶Pb/²⁰⁷Pb,²⁰⁶Pb/²⁰⁸Pb, and²⁰⁷Pb/²⁰⁸Pb in the tap water with those in various plumbing materials. The comparisons revealed that the source of Pb in most of the tap water samples was derived from copper pipe or solder.     

应用多接收器电感耦合等离子体质谱法测定海洋碳酸盐中稳定铅同位素组成

研究了多接收器电感耦合等离子体质谱仪(MC-ICP MS)测定铅同位素比值时,影响测试结果准确度和精密度的主要因素及其优化过程。在优化条件下,10 h内连续30次测定4 ng/mL NIST SRM 981同位素标准溶液铅同位素比值,获得208Pb/206Pb、207Pb/206Pb和206Pb/204Pb相对标准偏差(RSDs)分别为0.005%、0.004%和0.054%。长期监测208Pb/206Pb、207Pb/206Pb和206Pb/204Pb,标准偏差(2SDs)分别为0.000 06、0.000 05和0.006 7。采用NEPTUNE MC-ICP MS法测定了低铅海洋碳酸盐样品中稳定铅的同位素比值,并对南海橙黄滨珊瑚(Porites lutea)和库氏砗磲(Tridacna gigas)进行了分析,得到全流程空白为8～10 pg,重复样误差优于0.1%。经0.50 mol/L HNO3洗脱之后,得到海南珊瑚样品中208Pb/206Pb、207Pb/206Pb的比值分别为2.086 2±0.001 5、0.849 90±0.001 47(n=16);海南砗磲样品中208Pb/206Pb、207Pb/206Pb的比值分别为2.116 9±0.004 2、0.864 81±0.001 62(n=9)。进一步考察了南海海洋碳酸盐中204Pb的同位素比值。分析结果表明,南海海洋碳酸盐中稳定铅同位素比值与中国气溶胶、珠江三角洲大气沉降、黄土及南海海底玄武岩等具有很好的相关性。方法适用于复杂基体高钙低铅的海洋碳酸盐样品中铅同位素比值的分析。     

Application of routine estimation of Pb isotopic ratios by inductively coupled plasma mass spectrometry for studying the Pb origin in hair of children living in polluted areas. A pilot study

The analysis of ²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb isotope ratios for environmental Pb markers (leaded gasoline, air-borne particulate matter, house window dust) and hair of children was undertaken by the routine quadrupole inductively coupled argon plasma mass spectrometry (Q-ICP-MS). Hair samples collected from 10-year-old children living in Krakow in 1995 and 35 randomly selected children, aged 11, both sexes were included in the current study. Air-borne particles were collected by PM-2.5 (an aerodynamic diameter dac <2.5 μm) and PM-10 (fraction with an dac <10 μm) samplers in the proximity of steel factories situated near Krakow. Imprecision of routine estimations was approximately 0.6–0.7% or less, and was the lowest for the ²⁰⁷Pb/²⁰⁸Pb ratio (approx. 0.2%). These conditions were sufficient to distinguish Pb from air-borne dust from that in gasoline or window dust. No differences were found between Pb in PM-2.5 and PM-10 particles. The associations of the Pb in the these environmental sources and that in hair of children were discussed. The relationships of the Pb isotope ratios and other parameters related to environmental pollution were also analyzed. The analysis of distribution of the ²⁰⁷Pb/²⁰⁸Pb ratio in the hair of children, provided some evidence of the fact that hair lead of approximately 20% of the investigated population could arise from gasoline, while the Pb from air-borne dust and remaining sources can be attributed to approximately 80% of the population.     

A rapid and reliable method for Pb isotopic analysis of peat and lichens by laser ablation-quadrupole-inductively coupled plasma-mass spectrometry for biomonitoring and sample screening

An analytical protocol for rapid and reliable laser ablation-quadrupole (LA-Q)- and multi-collector (MC-) inductively coupled plasma-mass spectrometry (ICP-MS) analysis of Pb isotope ratios (²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb) in peats and lichens is developed. This technique is applicable to source tracing atmospheric Pb deposition in biomonitoring studies and sample screening. Reference materials and environmental samples were dry ashed and pressed into pellets for introduction by laser ablation. No binder was used to reduce contamination. LA-MC-ICP-MS internal and external precisions were <1.1% and <0.3%, respectively, on both ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios. LA-Q-ICP-MS internal precisions on ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios were lower with values for the different sample sets <14.3% while external precisions were <2.9%. The level of external precision acquired in this study is high enough to distinguish between most modern Pb sources. LA-MC-ICP-MS measurements differed from thermal ionisation mass spectrometry (TIMS) values by 1% or less while the accuracy obtained using LA-Q-ICP-MS compared to solution MC-ICP-MS was 3.1% or better using a run bracketing (RB) mass bias correction method. Sample heterogeneity and detector switching when measuring ²⁰⁸Pb by Q-ICP-MS are identified as sources of reduced analytical performance.     

Determination of lead concentrations and isotope ratios in recent snow samples from high alpine sites with a double focusing ICP-MS

A double focusing ICP-MS, equipped with a Micro Concentric Nebulizer, has been used to determine concentrations and isotopic ratios of lead in recent snow samples (1993–1996) from high alpine sites in Switzerland. Concentrations varied between 0.02 ± 0.002 and 5.5 ± 0.15 ng/g and are slightly lower than concentrations reported by Atteia [1], by Batifol et al. [2], and by Wagenbach et al. [3] for precipitation samples from similar remote sites in Europe. Since concentrations of lead in the fresh snow samples were mainly in the lower pg/g range, the method to determine the isotopic ratios ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb had to be optimized. They could finally be determined with an average standard error of 0.14% within 12 min and a total sample consumption of 0.8 mL. The average ratios ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb were 0.875 and 2.117, respectively. These values are comparable to isotopic compositions of lead in aerosols collected in Western Europe [4] and are less radiogenic than predicted by Grousset et al. [5]. Our data indicate that, although lead emissions from traffic have decreased largely during the last 10 years, the contribution from this source in modern snow is still detectable and seems to be equal to the lead input from other anthropogenic sources (e.g. waste incineration, industry).     

ICP-MS测定土壤中铅同位素比值及地域差异性比较

建立用HNO_3-H_2O_2-HF体系微波消解前处理样品,利用电感耦合等离子体质谱测定土壤中铅同住素比值的方法,探讨并优化了影响测试结果的两种干扰因素.该方法中~(207)Pb/~(206)Pb和~(208)Pb/~(206)Pb的短期测量稳定性RSD分别达到0.12%和0.13%,长期测量的偏差分别在0.002和0.01以内,样品测量的最佳范围是10～40μg/L.采用标样-样品交叉法测定了湖南、湖北、云南、贵州、河南、福建、辽宁7个省的48个地区土壤中的铅同位素比值,结合聚类分析和主成分分析比较了各省土壤中同位素分布的差异,初步探讨了利用~(207)Pb/~(206)Pb和~(208)Pb/~(206)Pb比较烟叶产区的可能性.     

不同赋存形态土壤铅同位素比值用于判别地域性差异的研究

由于各地区地质结构不同,造成了铅同位素组成具有地域特征。本研究利用电感耦合等离子体质谱测定了福建不同茶园土壤的铅同位素比值,比较了土壤全消解和残渣态两种赋存形态的铅同位素比值的差异,发现残渣态的铅的地域性特征较强,可用来作为地区土壤的判别依据。     

Lead isotope measurements on aerosol samples with ICP-MS

Size fractionated aerosols were collected with low pressure Berner impactors on a radio/TV tower 110 m above ground on a hill 10 km east of Bern at a total elevation of 1060 m asl. Two different wind sectors were chosen with the goal of assessing any differences in lead concentration and the 3 radiogenic lead isotopes (206,207,208) for east and west wind, respectively. A leaching technique was used to extract the lead quantitatively from the surface of the impaction foils. This method has been proven to be better suited for airborne particles than complete microwave digestion because it is less time consuming and contamination risk is smaller. Blank considerations played a major role in choosing all the chemicals, tubes, beakers and selecting the analytical method. Lead concentrations were determined with GF-AAS and lead isotopes with two different ICP-MS systems, one being a multicollector system. Precision of the simultaneous multicollector system was found to be at least a factor of 3 better than that of the sequentially operating ICP-MS. The small variations in isotope ratios from the two wind sectors can be distinctly seen with this enhanced precision. The observed relative difference in isotope ratios between east- and westwind was ～0.6% for ²⁰⁷Pb/²⁰⁶Pb and ～0.5% for ²⁰⁸Pb/²⁰⁶Pb.     

11th International Conference on Methods and Applications of Radioanalytical Chemistry (MARC XI) introduction

Nuclear terrorism has led to newer investigative methods for building national nuclear forensic libraries. The objective of this work was to resolve these signatures by applying the ICP-MS for isotope ratio (IR) analysis on uranium containing samples. Lead (Pb) isotope ratios for the studied gold mine has ²⁰⁷Pb/²⁰⁴Pb values between 13–20 and ²⁰⁶Pb/²⁰⁴Pb values ranging from 16–25, which confirm that the Carletonville gold fields are of uraninite detrital pyrite deposits. Trace elemental concentrations indicated a pyrite type of uranium deposit. Uranium in the deposit exhibits geochemical signatures of the radiogenic formations of the ore enhanced in ²⁰⁶Pb.     

Isotopic Characterization of Lead in the Scottish Upland Environment

Abstract

Experimental plots have been set up at two Research Stations in upland areas of Scotland with the intention of characterising environmental samples using lead isotopic composition which varies according to the original source of the lead. Thermal ionisation mass spectrometry (TIMS) was used to measure lead isotope ratios with high precision. The ²⁰⁶Pb/²⁰⁷Pb ratios in rainwater were in the range from 1.101 to 1.153 over a period of two years at the two sites. Low ratios were associated with the very low ratios found in Britain in petrol additives during that period whereas higher ratios indicated a larger component derived from industrial sources at the Hartwood site. The ²⁰⁶Pb/²⁰⁷Pb ratios in the surface (0–2.5 cm) soil from a roadside plot were low (1.1126 and 1.1159 in 1989 and 1990, respectively) but the ratios in surface soils in plots distant from the road were considerably higher. Whereas the lead in roadside soil had a ²⁰⁶Pb/²⁰⁷Pb ratio indicating its source to be predominantly in recent petrol lead, there were significant components from other sources in the soils away from the road. The washing of grass samples resulted in no significant change in the lead isotope ratios. The lead isotope ratios measured in grass samples reflect the isotopic character of current atmospheric inputs but those in surface soil samples are an integrated record of atmospheric deposition over a long period of time. An undisturbed plot under a tree canopy had high concentrations of lead in the surface soil and low ²⁰⁶Pb/²⁰⁷Pb ratios. The ratios in fallen leaves on this plot were slightly but significantly lower than those in the grass grown on the plot. It would appear that the tree canopy is effective at scavenging lead carried in the atmosphere.     

Precise and accurate determination of lead isotope ratios in mining wastes by ICP-QMS as a tool to identify their source

A methodology for a precise and accurate determination of lead isotope ratios in mining wastes by inductively coupled plasma quadrupole-based mass spectrometry (ICP-QMS) has been developed. The study of instrumental bias factors led to the conclusion that internal correction to compensate mass discrimination is required as well as an interference equation correction when Hg is present. The proposed method has been applied to determine lead isotope ratios in several mining wastes, soils and sediments collected at three mining areas in Spain (Aran Valley, Cartagena and Osor).Statistical analysis highlights that ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb lead isotope ratios can be used as a fingerprint of mining waste origin which is related to the geological age of the lead ore.On the other hand, no statistically significant isotopic differences between original ore samples (galena) and processing wastes within a mining district were found, corroborating a unique lead source. Moreover, the lead isotopic composition of soil and sediment samples collected at the studied mining areas is close to that determined in the mining tailings from the same areas, suggesting that the unusual high content of lead in these samples is derived from mining activities rather than from other lead sources.     

Evaluation of extraction/digestion techniques used to determine lead isotopic composition in forest soils

Lead isotopic studies in soils provide an efficient tool for tracing the sources of lead pollution. Five different extraction/digestion techniques (0.05 M EDTA, 0.5 M HNO₃, 2 M HNO₃, aqua regia, total digestion) were used for lead isotopic composition (²⁰⁶Pb/²⁰⁷Pb) determination in three forest soil profiles with different kinds of prevailing Pb contamination (unpolluted area, smelting area and vicinity of a motorway). The results obtained showed that all extraction/digestion methods used for the determination of ²⁰⁶Pb/²⁰⁷Pb ratios in surface horizons containing high organic matter contents gave statistically identical values (according to the Tukey test). In mineral soil horizons, differences between the individual extraction/digestion methods could be observed (the lowest ²⁰⁶Pb/²⁰⁷Pb ratios were obtained from EDTA extracts, corresponding to weakly bound anthropogenic lead, and the highest ²⁰⁶Pb/²⁰⁷Pb ratios were obtained from total digestion). The combination of total digestion and EDTA extraction (labile lead fraction) seems to be the optimal combination for ²⁰⁶Pb/²⁰⁷Pb ratio determination and optimal result interpretation.     

Temporal evolution of lead isotope ratios and metal concentrations in sediments of the north Aegean Sea,in Turkish coast

In present research, fifteen surficial and two profile sediment samples were studied in terms of sediment chronology and pollution degree on the ground of pollution indexes such as enrichment factor (EF), contamination factor (CF), Pollution Load Index (PLI) and lead isotope ratios (²⁰⁶Pb/²⁰⁷Pb, ²⁰⁸Pb/²⁰⁶Pb). Lead-210 (polonium-210) activity concentrations were measured by utilizing alpha spectrometry. Sediment chronology was determined via modified CRS mathematical model. Average mass accumulation rates are 0.301 and 0.227 g cm^?2 year^?1 in Bak?rçay River mouth and Ayval?k offshore stations respectively. Mass accumulation rates do not display the systematic increases along the cores from bottom layers to top layers. In Bak?rçay River mouth station ²¹⁰Pb flux is higher than the range of global atmospheric ²¹⁰Pb flux value. Due to the high CF and EF values of Sr both of stations have hydrothermal features. Ayval?k offshore station has displayed Na, Cd pollution since 1945, but Na, Cd, As, Mo, Ag pollutions have existed in Bak?rçay River mouth station since 1983 in terms of CF and EF values. According to PLI index, Bak?rçay River mouth station has “starting level pollution” degree and it displayed an “acute corruption” in 1981. ²⁰⁶Pb/²⁰⁷Pb ratios range from 1.17 to 1.25, ²⁰⁸Pb/²⁰⁶Pb ratios range from 1.99 to 2.16 in study area. When ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb ratios are evaluated with together, it is seen that both of the stations have had the natural (geologic) sediments since 2011.     

Isotopic fingerprint method: Assessment of the origin of rare earth compounds from the isotope ratios of lead impurities

The isotope ratios ²⁰⁷Pb:²⁰⁶Pb and ²⁰⁸Pb: ²⁰⁶Pb are measured by means of inductively coupled plasma mass spectrometry (ICP-MS) for monazite minerals and commercial rare earth compounds and are evaluated with respect to the initial composition of the minerals and the origin of the samples. The application of the isotopic fingerprint method is demonstrated.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday     

电感耦合等离子体质谱测定地质样品中Pb同位素比值

铅有 4个天然的同位素 ,由于放射衰变、宇宙的辐射及人类的活动 ,使 2 0 6Pb/2 0 4 Pb,2 0 7Pb/2 0 4 Pb及2 0 8Pb/2 0 4 Pb值在自然界中呈现相应的变化 ,而这种变化使得铅同位素成为一种有效的示踪手段和地质年代学研究的工具 ,同时在环境质量监控、放射性污染追踪及人类社会的变迁等方面有着广泛应用 .热电离质谱 (TIMS)分析技术对于大多数的同位素比值测定具有极高的精密度和准确度 ,但对于铅的测定由于难以获得一个高度浓缩且稳定不变的同位素作为内标进行质量偏移校正 [1] ,使其测定的准确度受到影响 .Rehkamper等 [2 ,3 ] 研究了…